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Hajra D, Yadav V, Singh A, Chakravortty D. SIRT1 and SIRT3 Impact Host Mitochondrial Function and Host Salmonella pH Balance during Infection. ACS Infect Dis 2025; 11:827-843. [PMID: 40168249 DOI: 10.1021/acsinfecdis.4c00751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2025]
Abstract
Mitochondria are important organelles that regulate energy homeostasis. Mitochondrial health and dynamics are crucial determinants of the outcome of several bacterial infections. SIRT3, a major mitochondrial sirtuin, along with SIRT1 regulates key mitochondrial functions. This led to considerable interest in understanding the role of SIRT1 and SIRT3 in governing mitochondrial functions during Salmonella infection. Here, we show that loss of SIRT1 and SIRT3 function either by shRNA-mediated knockdown or by inhibitor treatment led to increased mitochondrial dysfunction with alteration in mitochondrial bioenergetics alongside increased mitochondrial superoxide generation in Salmonella-infected macrophages. Consistent with dysfunctional mitochondria, mitophagy was induced along with altered mitochondrial fusion-fission dynamics in S. typhimurium-infected macrophages. Additionally, the mitochondrial bioenergetic alteration promotes acidification of the infected macrophage cytosolic pH. This host cytosolic pH imbalance skewed the intraphagosomal and intrabacterial pH in the absence of SIRT1 and SIRT3, resulting in decreased SPI-2 gene expression. Our results suggest a novel role for SIRT1 and SIRT3 in maintaining the intracellular Salmonella niche by modulating the mitochondrial bioenergetics and dynamics in the infected macrophages.
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Affiliation(s)
- Dipasree Hajra
- Department of Microbiology & Cell Biology, Indian Institute of Science, Bangalore 560012, India
| | - Vikas Yadav
- Department of Microbiology & Cell Biology, Indian Institute of Science, Bangalore 560012, India
| | - Amit Singh
- Department of Microbiology & Cell Biology, Indian Institute of Science, Bangalore 560012, India
| | - Dipshikha Chakravortty
- Department of Microbiology & Cell Biology, Indian Institute of Science, Bangalore 560012, India
- Adjunct Faculty, School of Biology, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala 695551, India
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2
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Castanheira S, Torronteras S, Cestero JJ, García-del Portillo F. Morphogenetic penicillin-binding proteins control virulence-associated type III secretion systems in Salmonella. Infect Immun 2025; 93:e0055524. [PMID: 39745378 PMCID: PMC11834469 DOI: 10.1128/iai.00555-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2024] [Accepted: 12/09/2024] [Indexed: 02/19/2025] Open
Abstract
Type III protein secretion systems (T3SSs) function as multiprotein devices that span the envelope of Gram-negative bacteria using the peptidoglycan (PG) layer as scaffold. This spatial arrangement explains why modifications in PG structure can alter T3SS activity. In Salmonella, incorporation of non-canonical D-amino acids in the PG was shown to decrease the activity of the T3SS encoded by the pathogenicity island-1 (SPI-1) without affecting other T3SS, like the flagellum apparatus. Enigmatically, following invasion of host cell Salmonella enterica serovar Typhimurium modifies PG synthesis by upregulating two pathogen-specific enzymes, the penicillin-binding proteins PBP2SAL and PBP3SAL, with roles in cell elongation and division, respectively. In the mouse typhoid model, the amount of PBP2SAL and PBP3SAL produced by the pathogen exceeds by large those of the canonical enzymes PBP2 and PBP3. This change responds to acidity and high osmolarity, the same cues that intra-phagosomal S. Typhimurium perceives to switch the SPI-1 T3SS by that encoded in SPI-2. Using isogenic mutants lacking each of the four morphogenetic PBPs, we tested whether their activities and those of the T3SS encoded by SPI-1 and SPI-2, are interconnected. Our data show that PBP2 is required for proper function of SPI-1 T3SS but dispensable for motility, whereas the lack of any of the morphogenetic PBPs increases SPI-2 T3SS activity. The positive control exerted by PBP2 on SPI-1 takes place via the SPI-1-specific regulators HilA and InvF. To our knowledge, these findings provide the first evidence linking morphogenetic enzymes that synthesize PG with T3SS associated to virulence.
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Affiliation(s)
- Sónia Castanheira
- Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
| | - Sara Torronteras
- Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
| | - Juan J. Cestero
- Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
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3
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Raj D, Nair AV, Singh A, Basu S, Sarkar K, Sharma J, Sharma S, Sharma S, Rathore M, Singh S, Prakash S, Simran, Sahu S, Kaushik AC, Siddiqi MI, Ghoshal UC, Chandra T, Bhosale V, Dasgupta A, Gupta SK, Verma S, Guha R, Chakravortty D, Ammanathan V, Lahiri A. Salmonella Typhimurium effector SseI regulates host peroxisomal dynamics to acquire lysosomal cholesterol. EMBO Rep 2025; 26:656-689. [PMID: 39695325 PMCID: PMC11811301 DOI: 10.1038/s44319-024-00328-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 10/16/2024] [Accepted: 10/25/2024] [Indexed: 12/20/2024] Open
Abstract
Salmonella enterica serotype Typhimurium (Salmonella) resides and multiplies intracellularly in cholesterol-rich compartments called Salmonella-containing vacuoles (SCVs) with actin-rich tubular extensions known as Salmonella-induced filaments (SIFs). SCV maturation depends on host-derived cholesterol, but the transport mechanism of low-density lipoprotein (LDL)-derived cholesterol to SCVs remains unclear. Here we find that peroxisomes are recruited to SCVs and function as pro-bacterial organelle. The Salmonella effector protein SseI is required for the interaction between peroxisomes and the SCV. SseI contains a variant of the PTS1 peroxisome-targeting sequence, GKM, localizes to the peroxisomes and activates the host Ras GTPase, ADP-ribosylation factor-1 (ARF-1). Activation of ARF-1 leads to the recruitment of phosphatidylinsolitol-5-phosphate-4 kinase and the generation of phosphatidylinsolitol-4-5-bisphosphate on peroxisomes. This enhances the interaction of peroxisomes with lysosomes and allows for the transfer of lysosomal cholesterol to SCVs using peroxisomes as a bridge. Salmonella infection of peroxisome-depleted cells leads to the depletion of cholesterol on the SCVs, resulting in reduced SIF formation and bacterial proliferation. Taken together, our work identified peroxisomes as a target of Salmonella secretory effectors, and as conveyance of host cholesterol to enhance SCV stability, SIF integrity, and intracellular bacterial growth.
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Affiliation(s)
- Desh Raj
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Abhilash Vijay Nair
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India
| | - Anmol Singh
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India
| | - Swarnali Basu
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Kabita Sarkar
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Jyotsna Sharma
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Shiva Sharma
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Sanmi Sharma
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Manisha Rathore
- Laboratory Animal Facility Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Shriya Singh
- Molecular Microbiology and Immunology Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Shakti Prakash
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Simran
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- Neuroscience & Ageing Biology Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Shikha Sahu
- Department of Gastroenterology, Sanjay Gandhi Postgraduate Institute of Medicine, Lucknow, India
| | - Aman Chandra Kaushik
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Mohammad Imran Siddiqi
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Uday C Ghoshal
- Department of Gastroenterology, Sanjay Gandhi Postgraduate Institute of Medicine, Lucknow, India
| | - Tulika Chandra
- Department of Transfusion Medicine, King Georges' Medical University, Lucknow, India
| | - Vivek Bhosale
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- Toxicology and Experimental Medicine Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Arunava Dasgupta
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- Molecular Microbiology and Immunology Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Shashi Kumar Gupta
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Sonia Verma
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- Neuroscience & Ageing Biology Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Rajdeep Guha
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- Laboratory Animal Facility Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Dipshikha Chakravortty
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
| | - Veena Ammanathan
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow, India.
| | - Amit Lahiri
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India.
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Han J, Aljahdali N, Zhao S, Tang H, Harbottle H, Hoffmann M, Frye JG, Foley SL. Infection biology of Salmonella enterica. EcoSal Plus 2024; 12:eesp00012023. [PMID: 38415623 PMCID: PMC11636313 DOI: 10.1128/ecosalplus.esp-0001-2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 07/31/2023] [Indexed: 02/29/2024]
Abstract
Salmonella enterica is the leading cause of bacterial foodborne illness in the USA, with an estimated 95% of salmonellosis cases due to the consumption of contaminated food products. Salmonella can cause several different disease syndromes, with the most common being gastroenteritis, followed by bacteremia and typhoid fever. Among the over 2,600 currently identified serotypes/serovars, some are mostly host-restricted and host-adapted, while the majority of serotypes can infect a broader range of host species and are associated with causing both livestock and human disease. Salmonella serotypes and strains within serovars can vary considerably in the severity of disease that may result from infection, with some serovars that are more highly associated with invasive disease in humans, while others predominantly cause mild gastroenteritis. These observed clinical differences may be caused by the genetic make-up and diversity of the serovars. Salmonella virulence systems are very complex containing several virulence-associated genes with different functions that contribute to its pathogenicity. The different clinical syndromes are associated with unique groups of virulence genes, and strains often differ in the array of virulence traits they display. On the chromosome, virulence genes are often clustered in regions known as Salmonella pathogenicity islands (SPIs), which are scattered throughout different Salmonella genomes and encode factors essential for adhesion, invasion, survival, and replication within the host. Plasmids can also carry various genes that contribute to Salmonella pathogenicity. For example, strains from several serovars associated with significant human disease, including Choleraesuis, Dublin, Enteritidis, Newport, and Typhimurium, can carry virulence plasmids with genes contributing to attachment, immune system evasion, and other roles. The goal of this comprehensive review is to provide key information on the Salmonella virulence, including the contributions of genes encoded in SPIs and plasmids during Salmonella pathogenesis.
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Affiliation(s)
- Jing Han
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
| | - Nesreen Aljahdali
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
- Biological Science Department, College of Science, King Abdul-Aziz University, Jeddah, Saudi Arabia
| | - Shaohua Zhao
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Rockville, Maryland, USA
| | - Hailin Tang
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
| | - Heather Harbottle
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Rockville, Maryland, USA
| | - Maria Hoffmann
- Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, Maryland, USA
| | - Jonathan G. Frye
- Agricutlutral Research Service, U.S. Department of Agriculture, Athens, Georgia, USA
| | - Steven L. Foley
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
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Wimmi S, Fleck M, Helbig C, Brianceau C, Langenfeld K, Szymanski WG, Angelidou G, Glatter T, Diepold A. Pilotins are mobile T3SS components involved in assembly and substrate specificity of the bacterial type III secretion system. Mol Microbiol 2024; 121:304-323. [PMID: 38178634 DOI: 10.1111/mmi.15223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 12/17/2023] [Accepted: 12/20/2023] [Indexed: 01/06/2024]
Abstract
In animal pathogens, assembly of the type III secretion system injectisome requires the presence of so-called pilotins, small lipoproteins that assist the formation of the secretin ring in the outer membrane. Using a combination of functional assays, interaction studies, proteomics, and live-cell microscopy, we determined the contribution of the pilotin to the assembly, function, and substrate selectivity of the T3SS and identified potential new downstream roles of pilotin proteins. In absence of its pilotin SctG, Yersinia enterocolitica forms few, largely polar injectisome sorting platforms and needles. Accordingly, most export apparatus subcomplexes are mobile in these strains, suggesting the absence of fully assembled injectisomes. Remarkably, while absence of the pilotin all but prevents export of early T3SS substrates, such as the needle subunits, it has little effect on secretion of late T3SS substrates, including the virulence effectors. We found that although pilotins interact with other injectisome components such as the secretin in the outer membrane, they mostly localize in transient mobile clusters in the bacterial membrane. Together, these findings provide a new view on the role of pilotins in the assembly and function of type III secretion injectisomes.
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Affiliation(s)
- Stephan Wimmi
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Moritz Fleck
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Carlos Helbig
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Corentin Brianceau
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Katja Langenfeld
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Witold G Szymanski
- Mass Spectrometry and Proteomics Facility, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Georgia Angelidou
- Mass Spectrometry and Proteomics Facility, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Timo Glatter
- Mass Spectrometry and Proteomics Facility, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Andreas Diepold
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
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Xiong D, Song L, Chen Y, Jiao X, Pan Z. Salmonella Enteritidis activates inflammatory storm via SPI-1 and SPI-2 to promote intracellular proliferation and bacterial virulence. Front Cell Infect Microbiol 2023; 13:1158888. [PMID: 37325511 PMCID: PMC10266283 DOI: 10.3389/fcimb.2023.1158888] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Accepted: 05/18/2023] [Indexed: 06/17/2023] Open
Abstract
Salmonella Enteritidis is an important intracellular pathogen, which can cause gastroenteritis in humans and animals and threaten life and health. S. Enteritidis proliferates in host macrophages to establish systemic infection. In this study, we evaluated the effects of Salmonella pathogenicity island-1 (SPI-1) and SPI-2 to S. Enteritidis virulence in vitro and in vivo, as well as the host inflammatory pathways affected by SPI-1 and SPI-2. Our results show that S. Enteritidis SPI-1 and SPI-2 contributed to bacterial invasion and proliferation in RAW264.7 macrophages, and induced cytotoxicity and cellular apoptosis of these cells. S. Enteritidis infection induced multiple inflammatory responses, including mitogen-activated protein kinase (ERK-mediated) and Janus kinase-signal transducer and activator of transcript (STAT) (STAT2-mediated) pathways. Both SPI-1 and SPI-2 were necessary to induce robust inflammatory responses and ERK/STAT2 phosphorylation in macrophages. In a mouse infection model, both SPIs, especially SPI-2, resulted in significant production of inflammatory cytokines and various interferon-stimulated genes in the liver and spleen. Activation of the ERK- and STAT2-mediated cytokine storm was largely affected by SPI-2. S. Enteritidis ΔSPI-1-infected mice displayed moderate histopathological damage and drastically reduced bacterial loads in tissues, whereas only slight damage and no bacteria were observed in ΔSPI-2- and ΔSPI-1/SPI-2-infected mice. A survival assay showed that ΔSPI-1 mutant mice maintained a medium level of virulence, while SPI-2 plays a decisive role in bacterial virulence. Collectively, our findings indicate that both SPIs, especially SPI-2, profoundly contributed to S. Enteritidis intracellular localization and virulence by activating multiple inflammatory pathways.
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Affiliation(s)
- Dan Xiong
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture and Rural Affairs, Yangzhou University, Yangzhou, China
| | - Li Song
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture and Rural Affairs, Yangzhou University, Yangzhou, China
| | - Yushan Chen
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture and Rural Affairs, Yangzhou University, Yangzhou, China
| | - Xinan Jiao
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture and Rural Affairs, Yangzhou University, Yangzhou, China
| | - Zhiming Pan
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture and Rural Affairs, Yangzhou University, Yangzhou, China
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Browning KR, Merrikh H. Pathogenic bacteria experience pervasive RNA polymerase backtracking during infection. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.12.540596. [PMID: 37215019 PMCID: PMC10197661 DOI: 10.1101/2023.05.12.540596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Pathogenic bacteria and their eukaryotic hosts are in a constant arms race. Hosts have numerous defense mechanisms at their disposal that not only challenge the bacterial invaders, but have the potential to disrupt molecular transactions along the bacterial chromosome. However, it is unclear how the host impacts association of proteins with the bacterial chromosome at the molecular level during infection. This is partially due to the lack of a method that could detect these events in pathogens while they are within host cells. We developed and optimized a system capable of mapping and measuring levels of bacterial proteins associated with the chromosome while they are actively infecting the host (referred to as PIC-seq). Here, we focused on the dynamics of RNA polymerase (RNAP) movement and association with the chromosome in the pathogenic bacterium Salmonella enterica as a model system during infection. Using PIC-seq, we found that RNAP association patterns with the chromosome change during infection genome-wide, including at regions that encode for key virulence genes. Importantly, we found that infection of a host significantly increases RNAP backtracking on the bacterial chromosome. RNAP backtracking is the most common form of disruption to RNAP progress on the chromosome. Interestingly, we found that the resolution of backtracked RNAPs via the anti-backtracking factors GreA and GreB is critical for pathogenesis, revealing a new class of virulence genes. Altogether, our results strongly suggest that infection of a host significantly impacts transcription by disrupting RNAP movement on the chromosome within the bacterial pathogen. The increased backtracking events have important implications not only for efficient transcription, but also for mutation rates as stalled RNAPs increase the levels of mutagenesis.
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Affiliation(s)
- Kaitlyn R. Browning
- Vanderbilt University School of Medicine, Department of Biochemistry, Nashville, TN 37232, USA
| | - Houra Merrikh
- Vanderbilt University School of Medicine, Department of Biochemistry, Nashville, TN 37232, USA
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St. Louis BM, Quagliato SM, Lee PC. Bacterial effector kinases and strategies to identify their target host substrates. Front Microbiol 2023; 14:1113021. [PMID: 36846793 PMCID: PMC9950578 DOI: 10.3389/fmicb.2023.1113021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 01/25/2023] [Indexed: 02/12/2023] Open
Abstract
Post-translational modifications (PTMs) are critical in regulating protein function by altering chemical characteristics of proteins. Phosphorylation is an integral PTM, catalyzed by kinases and reversibly removed by phosphatases, that modulates many cellular processes in response to stimuli in all living organisms. Consequently, bacterial pathogens have evolved to secrete effectors capable of manipulating host phosphorylation pathways as a common infection strategy. Given the importance of protein phosphorylation in infection, recent advances in sequence and structural homology search have significantly expanded the discovery of a multitude of bacterial effectors with kinase activity in pathogenic bacteria. Although challenges exist due to complexity of phosphorylation networks in host cells and transient interactions between kinases and substrates, approaches are continuously being developed and applied to identify bacterial effector kinases and their host substrates. In this review, we illustrate the importance of exploiting phosphorylation in host cells by bacterial pathogens via the action of effector kinases and how these effector kinases contribute to virulence through the manipulation of diverse host signaling pathways. We also highlight recent developments in the identification of bacterial effector kinases and a variety of techniques to characterize kinase-substrate interactions in host cells. Identification of host substrates provides new insights for regulation of host signaling during microbial infection and may serve as foundation for developing interventions to treat infection by blocking the activity of secreted effector kinases.
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Affiliation(s)
- Brendyn M. St. Louis
- Department of Biological Sciences, College of Liberal Arts and Sciences, Wayne State University, Detroit, MI, United States
| | - Sydney M. Quagliato
- Department of Biological Sciences, College of Liberal Arts and Sciences, Wayne State University, Detroit, MI, United States
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9
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Roy Chowdhury A, Sah S, Varshney U, Chakravortty D. Salmonella Typhimurium outer membrane protein A (OmpA) renders protection from nitrosative stress of macrophages by maintaining the stability of bacterial outer membrane. PLoS Pathog 2022; 18:e1010708. [PMID: 35969640 PMCID: PMC9410544 DOI: 10.1371/journal.ppat.1010708] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Revised: 08/25/2022] [Accepted: 06/27/2022] [Indexed: 11/18/2022] Open
Abstract
Bacterial porins are highly conserved outer membrane proteins used in the selective transport of charged molecules across the membrane. In addition to their significant contributions to the pathogenesis of Gram-negative bacteria, their role(s) in salmonellosis remains elusive. In this study, we investigated the role of outer membrane protein A (OmpA), one of the major outer membrane porins of Salmonella, in the pathogenesis of Salmonella Typhimurium (STM). Our study revealed that OmpA plays an important role in the intracellular virulence of Salmonella. An ompA deficient strain of Salmonella (STM ΔompA) showed compromised proliferation in macrophages. We found that the SPI-2 encoded virulence factors such as sifA and ssaV are downregulated in STM ΔompA. The poor colocalization of STM ΔompA with LAMP-1 showed that disruption of SCV facilitated its release into the cytosol of macrophages, where it was assaulted by reactive nitrogen intermediates (RNI). The enhanced recruitment of nitrotyrosine on the cytosolic population of STM ΔompAΔsifA and ΔompAΔssaV compared to STM ΔsifA and ΔssaV showed an additional role of OmpA in protecting the bacteria from host nitrosative stress. Further, we showed that the generation of greater redox burst could be responsible for enhanced sensitivity of STM ΔompA to the nitrosative stress. The expression of several other outer membrane porins such as ompC, ompD, and ompF was upregulated in STM ΔompA. We found that in the absence of ompA, the enhanced expression of ompF increased the outer membrane porosity of Salmonella and made it susceptible to in vitro and in vivo nitrosative stress. Our study illustrates a novel mechanism for the strategic utilization of OmpA by Salmonella to protect itself from the nitrosative stress of macrophages.
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Affiliation(s)
- Atish Roy Chowdhury
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India
| | - Shivjee Sah
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India
| | - Umesh Varshney
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India
| | - Dipshikha Chakravortty
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India
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10
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Kriel NL, Newton-Foot M, Bennion OT, Aldridge BB, Mehaffy C, Belisle JT, Walzl G, Warren RM, Sampson SL, Gey van Pittius NC. Localization of EccA 3 at the growing pole in Mycobacterium smegmatis. BMC Microbiol 2022; 22:140. [PMID: 35590245 PMCID: PMC9118679 DOI: 10.1186/s12866-022-02554-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 05/09/2022] [Indexed: 11/30/2022] Open
Abstract
Background Bacteria require specialized secretion systems for the export of molecules into the extracellular space to modify their environment and scavenge for nutrients. The ESX-3 secretion system is required by mycobacteria for iron homeostasis. The ESX-3 operon encodes for one cytoplasmic component (EccA3) and five membrane components (EccB3 – EccE3 and MycP3). In this study we sought to identify the sub-cellular location of EccA3 of the ESX-3 secretion system in mycobacteria. Results Fluorescently tagged EccA3 localized to a single pole in the majority of Mycobacterium smegmatis cells and time-lapse fluorescent microscopy identified this pole as the growing pole. Deletion of ESX-3 did not prevent polar localization of fluorescently tagged EccA3, suggesting that EccA3 unipolar localization is independent of other ESX-3 components. Affinity purification - mass spectrometry was used to identify EccA3 associated proteins which may contribute to the localization of EccA3 at the growing pole. EccA3 co-purified with fatty acid metabolism proteins (FAS, FadA3, KasA and KasB), mycolic acid synthesis proteins (UmaA, CmaA1), cell division proteins (FtsE and FtsZ), and cell shape and cell cycle proteins (MurS, CwsA and Wag31). Secretion system related proteins Ffh, SecA1, EccA1, and EspI were also identified. Conclusions Time-lapse microscopy demonstrated that EccA3 is located at the growing pole in M. smegmatis. The co-purification of EccA3 with proteins known to be required for polar growth, mycolic acid synthesis, the Sec secretion system (SecA1), and the signal recognition particle pathway (Ffh) also suggests that EccA3 is located at the site of active cell growth. Supplementary Information The online version contains supplementary material available at 10.1186/s12866-022-02554-6.
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Affiliation(s)
- Nastassja L Kriel
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research; South African Medical Research Council Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa.
| | - Mae Newton-Foot
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research; South African Medical Research Council Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
| | - Owen T Bennion
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, 02111, USA
| | - Bree B Aldridge
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, 02111, USA
| | - Carolina Mehaffy
- Mycobacteria Research Laboratories, Department of Microbiology Immunology and Pathology, Colorado State University, Fort Collins, CO, 80523, USA
| | - John T Belisle
- Mycobacteria Research Laboratories, Department of Microbiology Immunology and Pathology, Colorado State University, Fort Collins, CO, 80523, USA
| | - Gerhard Walzl
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research; South African Medical Research Council Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
| | - Robin M Warren
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research; South African Medical Research Council Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
| | - Samantha L Sampson
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research; South African Medical Research Council Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
| | - Nico C Gey van Pittius
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research; South African Medical Research Council Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
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11
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Xu J, Wang J, Liu A, Zhang Y, Gao X. Structural and Functional Analysis of SsaV Cytoplasmic Domain and Variable Linker States in the Context of the InvA-SsaV Chimeric Protein. Microbiol Spectr 2021; 9:e0125121. [PMID: 34851139 PMCID: PMC8635156 DOI: 10.1128/spectrum.01251-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 11/05/2021] [Indexed: 11/20/2022] Open
Abstract
The type III secretion (T3S) injectisome is a syringe-like protein-delivery nanomachine widely utilized by Gram-negative bacteria. It can deliver effector proteins directly from bacteria into eukaryotic host cells, which is crucial for the bacterial-host interaction. Intracellular pathogen Salmonella enterica serovar Typhimurium encodes two sets of T3S injectisomes from Salmonella pathogenicity islands 1 and 2 (SPI-1 and SPI-2), which are critical for its host invasion and intracellular survival, respectively. The inner membrane export gate protein, SctV (InvA in SPI-1 and SsaV in SPI-2), is the largest component of the injectisome and is essential for assembly and function of T3SS. Here, we report the 2.11 Å cryo-EM structure of the SsaV cytoplasmic domain (SsaVC) in the context of a full-length SctV chimera consisting of the transmembrane region of InvA, the linker of SsaV (SsaVL) and SsaVC. The structural analysis shows that SsaVC exists in a semi-open state and SsaVL exhibits two major orientations, implying a highly dynamic process of SsaV for the substrate selection and secretion in a full-length context. A biochemical assay indicates that SsaVL plays an essential role in maintaining the nonameric state of SsaV. This study offers near atomic-level insights into how SsaVC and SsaVL facilitate the assembly and function of SsaV and may lead to the development of potential anti-virulence therapeutics against T3SS-mediated bacterial infection. IMPORTANCE Type III secretion system (T3SS) is a multicomponent nanomachine and a critical virulence factor for a wide range of Gram-negative bacterial pathogens. It can deliver numbers of effectors into the host cell to facilitate the bacterial host infection. Export gate protein SctV, as one of the engines of T3SS, is at the center of T3SS assembly and function. In this study, we show the high-resolution atomic structure of the cytosolic domain of SctV in the nonameric state with variable linker conformations. Our first observation of conformational changes of the linker region of SctV and the semi-open state of the cytosolic domain of SctV in the full-length context further support that the substrate selection and secretion process of SctV is highly dynamic. These findings have important implications for the development of therapeutic strategies targeting SctV to combat T3SS-mediated bacterial infection.
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Affiliation(s)
- Jinghua Xu
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China
| | - Jiuqing Wang
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China
| | - Aijun Liu
- Shanghai Fifth People's Hospital and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Yanqing Zhang
- Shanghai Fifth People's Hospital and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Xiang Gao
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China
- School of Life Sciences, Shandong University, Qingdao, China
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12
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Lisowski C, Dias J, Costa S, Silva RJ, Mano M, Eulalio A. Dysregulated endolysosomal trafficking in cells arrested in the G 1 phase of the host cell cycle impairs Salmonella vacuolar replication. Autophagy 2021; 18:1785-1800. [PMID: 34781820 DOI: 10.1080/15548627.2021.1999561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
Modulation of the host cell cycle has emerged as a common theme among the pathways regulated by bacterial pathogens, arguably to promote host cell colonization. However, in most cases the exact benefit ensuing from such interference to the infection process remains unclear. Previously, we have shown that Salmonella actively induces G2/M arrest of host cells, and that infection is severely inhibited in cells arrested in G1. In this study, we demonstrate that Salmonella vacuolar replication is inhibited in host cells blocked in G1, whereas the cytosolic replication of the closely related pathogen Shigella is not affected. Mechanistically, we show that cells arrested in G1, but not cells arrested in G2, present dysregulated endolysosomal trafficking, displaying an abnormal accumulation of vesicles positive for late endosomal and lysosomal markers. In addition, the macroautophagic/autophagic flux and degradative lysosomal function are strongly impaired. This endolysosomal trafficking dysregulation results in sustained activation of the SPI-1 type III secretion system and lack of vacuole repair by the autophagy pathway, ultimately compromising the maturation and integrity of the Salmonella-containing vacuole. As such, Salmonella is released in the host cytosol. Collectively, our findings demonstrate that the modulation of the host cell cycle occurring during Salmonella infection is related to a disparity in the permissivity of cells arrested in G1 and G2/M, due to their intrinsic characteristics.
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Affiliation(s)
- Clivia Lisowski
- Host RNA Metabolism Group, Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg, Germany
| | - Jane Dias
- RNA & Infection Laboratory, Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal.,Functional Genomics and RNA-based Therapeutics Laboratory, Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal.,PhD Programme in Experimental Biology and Biomedicine (PDBEB), Institute for Interdisciplinary Research (IIIUC), University of Coimbra, Coimbra, Portugal
| | - Susana Costa
- RNA & Infection Laboratory, Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal.,Functional Genomics and RNA-based Therapeutics Laboratory, Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal.,PhD Programme in Experimental Biology and Biomedicine (PDBEB), Institute for Interdisciplinary Research (IIIUC), University of Coimbra, Coimbra, Portugal
| | - Ricardo Jorge Silva
- Functional Genomics and RNA-based Therapeutics Laboratory, Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal.,PhD Programme in Experimental Biology and Biomedicine (PDBEB), Institute for Interdisciplinary Research (IIIUC), University of Coimbra, Coimbra, Portugal
| | - Miguel Mano
- Functional Genomics and RNA-based Therapeutics Laboratory, Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal.,Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - Ana Eulalio
- Host RNA Metabolism Group, Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg, Germany.,RNA & Infection Laboratory, Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal.,Department of Life Sciences, University of Coimbra, Coimbra, Portugal
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13
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Kim SI, Kim E, Yoon H. σ S-Mediated Stress Response Induced by Outer Membrane Perturbation Dampens Virulence in Salmonella enterica serovar Typhimurium. Front Microbiol 2021; 12:750940. [PMID: 34659184 PMCID: PMC8516096 DOI: 10.3389/fmicb.2021.750940] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 08/30/2021] [Indexed: 12/13/2022] Open
Abstract
Salmonella alters cellular processes as a strategy to improve its intracellular fitness during host infection. Alternative σ factors are known to rewire cellular transcriptional regulation in response to environmental stressors. σs factor encoded by the rpoS gene is a key regulator required for eliciting the general stress response in many proteobacteria. In this study, Salmonella Typhimurium deprived of an outer membrane protein YcfR was attenuated in intracellular survival and exhibited downregulation in Salmonella pathogenicity island-2 (SPI-2) genes. This decreased SPI-2 expression caused by the outer membrane perturbation was abolished in the absence of rpoS. Interestingly, regardless of the defects in the outer membrane integrity, RpoS overproduction decreased transcription from the common promoter of ssrA and ssrB, which encode a two-component regulatory system for SPI-2. RpoS was found to compete with RpoD for binding to the PssrA region, and its binding activity with RNA polymerase (RNAP) to form Eσs holoenzyme was stimulated by the small regulatory protein Crl. This study demonstrates that Salmonella undergoing RpoS-associated stress responses due to impaired envelope integrity may reciprocally downregulate the expression of SPI-2 genes to reduce its virulence.
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Affiliation(s)
- Seul I Kim
- Department of Molecular Science and Technology, Ajou University, Suwon, South Korea
| | - Eunsuk Kim
- Department of Molecular Science and Technology, Ajou University, Suwon, South Korea
| | - Hyunjin Yoon
- Department of Molecular Science and Technology, Ajou University, Suwon, South Korea.,Department of Applied Chemistry and Biological Engineering, Ajou University, Suwon, South Korea
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14
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Singh MK, Zangoui P, Yamanaka Y, Kenney LJ. Genetic code expansion enables visualization of Salmonella type three secretion system components and secreted effectors. eLife 2021; 10:67789. [PMID: 34061032 PMCID: PMC8192122 DOI: 10.7554/elife.67789] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 05/22/2021] [Indexed: 12/14/2022] Open
Abstract
Type three secretion systems enable bacterial pathogens to inject effectors into the cytosol of eukaryotic hosts to reprogram cellular functions. It is technically challenging to label effectors and the secretion machinery without disrupting their structure/function. Herein, we present a new approach for labeling and visualization of previously intractable targets. Using genetic code expansion, we site-specifically labeled SsaP, the substrate specificity switch, and SifA, a here-to-fore unlabeled secreted effector. SsaP was secreted at later infection times; SsaP labeling demonstrated the stochasticity of injectisome and effector expression. SifA was labeled after secretion into host cells via fluorescent unnatural amino acids or non-fluorescent labels and a subsequent click reaction. We demonstrate the superiority of imaging after genetic code expansion compared to small molecule tags. It provides an alternative for labeling proteins that do not tolerate N- or C-terminal tags or fluorophores and thus is widely applicable to other secreted effectors and small proteins.
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Affiliation(s)
- Moirangthem Kiran Singh
- Mechanobiology Institute, T-Lab, 5A Engineering Drive 1, National University of Singapore, Singapore, Singapore.,Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, United States
| | - Parisa Zangoui
- Mechanobiology Institute, T-Lab, 5A Engineering Drive 1, National University of Singapore, Singapore, Singapore.,Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, United States
| | - Yuki Yamanaka
- Mechanobiology Institute, T-Lab, 5A Engineering Drive 1, National University of Singapore, Singapore, Singapore
| | - Linda J Kenney
- Mechanobiology Institute, T-Lab, 5A Engineering Drive 1, National University of Singapore, Singapore, Singapore.,Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, United States
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15
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Matthews-Palmer TRS, Gonzalez-Rodriguez N, Calcraft T, Lagercrantz S, Zachs T, Yu XJ, Grabe GJ, Holden DW, Nans A, Rosenthal PB, Rouse SL, Beeby M. Structure of the cytoplasmic domain of SctV (SsaV) from the Salmonella SPI-2 injectisome and implications for a pH sensing mechanism. J Struct Biol 2021; 213:107729. [PMID: 33774138 PMCID: PMC8223533 DOI: 10.1016/j.jsb.2021.107729] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 03/19/2021] [Accepted: 03/20/2021] [Indexed: 12/22/2022]
Abstract
CryoEM of a full-length type III secretion system SctV resolves cytoplasmic but not transmembrane domains. MD simulations show SctV protomers flexibly hinge. Acidification expands the SctV ring by altering interprotomer interactions.
Bacterial type III secretion systems assemble the axial structures of both injectisomes and flagella. Injectisome type III secretion systems subsequently secrete effector proteins through their hollow needle into a host, requiring co-ordination. In the Salmonella enterica serovar Typhimurium SPI-2 injectisome, this switch is triggered by sensing the neutral pH of the host cytoplasm. Central to specificity switching is a nonameric SctV protein with an N-terminal transmembrane domain and a toroidal C-terminal cytoplasmic domain. A ‘gatekeeper’ complex interacts with the SctV cytoplasmic domain in a pH dependent manner, facilitating translocon secretion while repressing effector secretion through a poorly understood mechanism. To better understand the role of SctV in SPI-2 translocon-effector specificity switching, we purified full-length SctV and determined its toroidal cytoplasmic region’s structure using cryo-EM. Structural comparisons and molecular dynamics simulations revealed that the cytoplasmic torus is stabilized by its core subdomain 3, about which subdomains 2 and 4 hinge, varying the flexible outside cleft implicated in gatekeeper and substrate binding. In light of patterns of surface conservation, deprotonation, and structural motion, the location of previously identified critical residues suggest that gatekeeper binds a cleft buried between neighboring subdomain 4s. Simulations suggest that a local pH change from 5 to 7.2 stabilizes the subdomain 3 hinge and narrows the central aperture of the nonameric torus. Our results are consistent with a model of local pH sensing at SctV, where pH-dependent dynamics of SctV cytoplasmic domain affect binding of gatekeeper complex.
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Affiliation(s)
| | | | - Thomas Calcraft
- Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom; Structural Biology of Cells and Viruses Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Signe Lagercrantz
- Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Tobias Zachs
- Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Xiu-Jun Yu
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
| | - Grzegorz J Grabe
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
| | - David W Holden
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
| | - Andrea Nans
- Structural Biology of Cells and Viruses Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Peter B Rosenthal
- Structural Biology of Cells and Viruses Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Sarah L Rouse
- Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom.
| | - Morgan Beeby
- Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom.
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16
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Milne-Davies B, Wimmi S, Diepold A. Adaptivity and dynamics in type III secretion systems. Mol Microbiol 2020; 115:395-411. [PMID: 33251695 DOI: 10.1111/mmi.14658] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 11/17/2020] [Accepted: 11/23/2020] [Indexed: 01/07/2023]
Abstract
The type III secretion system is the common core of two bacterial molecular machines: the flagellum and the injectisome. The flagellum is the most widely distributed prokaryotic locomotion device, whereas the injectisome is a syringe-like apparatus for inter-kingdom protein translocation, which is essential for virulence in important human pathogens. The successful concept of the type III secretion system has been modified for different bacterial needs. It can be adapted to changing conditions, and was found to be a dynamic complex constantly exchanging components. In this review, we highlight the flexibility, adaptivity, and dynamic nature of the type III secretion system.
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Affiliation(s)
- Bailey Milne-Davies
- Department of Ecophysiology, Max-Planck-Institute for Terrestrial Microbiology, Marburg, Germany
| | - Stephan Wimmi
- Department of Ecophysiology, Max-Planck-Institute for Terrestrial Microbiology, Marburg, Germany
| | - Andreas Diepold
- Department of Ecophysiology, Max-Planck-Institute for Terrestrial Microbiology, Marburg, Germany
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17
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Wang J, Brodmann M, Basler M. Assembly and Subcellular Localization of Bacterial Type VI Secretion Systems. Annu Rev Microbiol 2019; 73:621-638. [DOI: 10.1146/annurev-micro-020518-115420] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bacteria need to deliver large molecules out of the cytosol to the extracellular space or even across membranes of neighboring cells to influence their environment, prevent predation, defeat competitors, or communicate. A variety of protein-secretion systems have evolved to make this process highly regulated and efficient. The type VI secretion system (T6SS) is one of the largest dynamic assemblies in gram-negative bacteria and allows for delivery of toxins into both bacterial and eukaryotic cells. The recent progress in structural biology and live-cell imaging shows the T6SS as a long contractile sheath assembled around a rigid tube with associated toxins anchored to a cell envelope by a baseplate and membrane complex. Rapid sheath contraction releases a large amount of energy used to push the tube and toxins through the membranes of neighboring target cells. Because reach of the T6SS is limited, some bacteria dynamically regulate its subcellular localization to precisely aim at their targets and thus increase efficiency of toxin translocation.
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Affiliation(s)
- Jing Wang
- Biozentrum, University of Basel, CH 4056 Basel, Switzerland
| | - Maj Brodmann
- Biozentrum, University of Basel, CH 4056 Basel, Switzerland
| | - Marek Basler
- Biozentrum, University of Basel, CH 4056 Basel, Switzerland
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18
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Ashari KS, Roslan NS, Omar AR, Bejo MH, Ideris A, Mat Isa N. Genome sequencing and analysis of Salmonella enterica subsp. enterica serovar Stanley UPM 517: Insights on its virulence-associated elements and their potentials as vaccine candidates. PeerJ 2019; 7:e6948. [PMID: 31293824 PMCID: PMC6601603 DOI: 10.7717/peerj.6948] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 04/05/2019] [Indexed: 12/12/2022] Open
Abstract
Salmonella enterica subsp. enterica serovar Stanley (S. Stanley) is a pathogen that contaminates food, and is related to Salmonella outbreaks in a variety of hosts such as humans and farm animals through products like dairy items and vegetables. Despite the fact that several vaccines of Salmonella strains had been constructed, none of them were developed according to serovar Stanley up to this day. This study presents results of genome sequencing and analysis on our S. Stanley UPM 517 strain taken from fecal swabs of 21-day-old healthy commercial chickens in Perak, Malaysia and used Salmonella enterica subsp. enterica serovar Typhimurium LT2 (S. Typhimurium LT2) as a reference to be compared with. First, sequencing and assembling of the Salmonella Stanley UPM 517 genome into a contiguous form were done. The work was then continued with scaffolding and gap filling. Annotation and alignment of the draft genome was performed with S. Typhimurium LT2. The other elements of virulence estimated in this study included Salmonella pathogenicity islands, resistance genes, prophages, virulence factors, plasmid regions, restriction-modification sites and the CRISPR-Cas system. The S. Stanley UPM 517 draft genome had a length of 4,736,817 bp with 4,730 coding sequence and 58 RNAs. It was discovered via genomic analysis on this strain that there were antimicrobial resistance properties toward a wide variety of antibiotics. Tcf and ste, the two fimbrial virulence clusters related with human and broiler intestinal colonizations which were not found in S. Typhimurium LT2, were atypically discovered in the S. Stanley UPM 517 genome. These clusters are involved in the intestinal colonization of human and broilers, respectively. There were seven Salmonella pathogenicity islands (SPIs) within the draft genome, which contained the virulence factors associated with Salmonella infection (except SPI-14). Five intact prophage regions, mostly comprising of the protein encoding Gifsy-1, Fels-1, RE-2010 and SEN34 prophages, were also encoded in the draft genome. Also identified were Type I–III restriction-modification sites and the CRISPR-Cas system of the Type I–E subtype. As this strain exhibited resistance toward numerous antibiotics, we distinguished several genes that had the potential for removal in the construction of a possible vaccine candidate to restrain and lessen the pervasiveness of salmonellosis and to function as an alternative to antibiotics.
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Affiliation(s)
- Khalidah Syahirah Ashari
- Department of Cell and Molecular Biology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor, Malaysia
| | | | - Abdul Rahman Omar
- Institute of Bioscience, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.,Department of Veterinary Pathology and Microbiology, Faculty of Veterinary Medicine, Universiti Putra Malaysia, Serdang, Selangor, Malaysia
| | - Mohd Hair Bejo
- Institute of Bioscience, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.,Department of Veterinary Pathology and Microbiology, Faculty of Veterinary Medicine, Universiti Putra Malaysia, Serdang, Selangor, Malaysia
| | - Aini Ideris
- Institute of Bioscience, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.,Department of Veterinary Clinical Studies, Faculty of Veterinary Medicine, Universiti Putra Malaysia, Serdang, Selangor, Malaysia
| | - Nurulfiza Mat Isa
- Department of Cell and Molecular Biology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.,Institute of Bioscience, Universiti Putra Malaysia, Serdang, Selangor, Malaysia
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19
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Liew ATF, Foo YH, Gao Y, Zangoui P, Singh MK, Gulvady R, Kenney LJ. Single cell, super-resolution imaging reveals an acid pH-dependent conformational switch in SsrB regulates SPI-2. eLife 2019; 8:e45311. [PMID: 31033442 PMCID: PMC6557628 DOI: 10.7554/elife.45311] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 04/28/2019] [Indexed: 12/29/2022] Open
Abstract
After Salmonella is phagocytosed, it resides in an acidic vacuole. Its cytoplasm acidifies to pH 5.6; acidification activates pathogenicity island 2 (SPI-2). SPI-2 encodes a type three secretion system whose effectors modify the vacuole, driving endosomal tubulation. Using super-resolution imaging in single bacterial cells, we show that low pH induces expression of the SPI-2 SsrA/B signaling system. Single particle tracking, atomic force microscopy, and single molecule unzipping assays identified pH-dependent stimulation of DNA binding by SsrB. A so-called phosphomimetic form (D56E) was unable to bind to DNA in live cells. Acid-dependent DNA binding was not intrinsic to regulators, as PhoP and OmpR binding was not pH-sensitive. The low level of SPI-2 injectisomes observed in single cells is not due to fluctuating SsrB levels. This work highlights the surprising role that acid pH plays in virulence and intracellular lifestyles of Salmonella; modifying acid survival pathways represents a target for inhibiting Salmonella.
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Affiliation(s)
- Andrew Tze Fui Liew
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
| | - Yong Hwee Foo
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
| | - Yunfeng Gao
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
| | - Parisa Zangoui
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
| | | | - Ranjit Gulvady
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
| | - Linda J Kenney
- Mechanobiology Institute, T-LabNational University of SingaporeSingaporeSingapore
- Biochemistry and Molecular BiologyUniversity of Texas Medical BranchGalvestonUnited States
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20
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Kenney LJ. The role of acid stress in Salmonella pathogenesis. Curr Opin Microbiol 2019; 47:45-51. [DOI: 10.1016/j.mib.2018.11.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 11/10/2018] [Accepted: 11/15/2018] [Indexed: 11/29/2022]
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21
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Diepold A. Assembly and Post-assembly Turnover and Dynamics in the Type III Secretion System. Curr Top Microbiol Immunol 2019; 427:35-66. [PMID: 31218503 DOI: 10.1007/82_2019_164] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The type III secretion system (T3SS) is one of the largest transmembrane complexes in bacteria, comprising several intricately linked and embedded substructures. The assembly of this nanomachine is a hierarchical process which is regulated and controlled by internal and external cues at several critical points. Recently, it has become obvious that the assembly of the T3SS is not a unidirectional and deterministic process, but that parts of the T3SS constantly exchange or rearrange. This article aims to give an overview on the assembly and post-assembly dynamics of the T3SS, with a focus on emerging general concepts and adaptations of the general assembly pathway.
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Affiliation(s)
- Andreas Diepold
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Straße 10, 35043, Marburg, Germany.
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22
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SsaV Interacts with SsaL to Control the Translocon-to-Effector Switch in the Salmonella SPI-2 Type Three Secretion System. mBio 2018; 9:mBio.01149-18. [PMID: 30279280 PMCID: PMC6168863 DOI: 10.1128/mbio.01149-18] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Salmonella Typhimurium is an intracellular pathogen that uses the SPI-2 type III secretion system to deliver virulence proteins across the vacuole membrane surrounding intracellular bacteria. This involves a tightly regulated hierarchy of protein secretion controlled by two molecular switches. We found that SPI-2-encoded proteins SsaP and SsaU are involved in the first but not the second secretion switch. We identify key amino acids of the inner membrane protein SsaV that are required to interact with the so-called gatekeeper protein SsaL and show that the dissociation of SsaV-SsaL causes the second switch, leading to delivery of effector proteins. Our results provide insights into the molecular events controlling virulence-associated type III secretion and suggest a broader model describing how the process is regulated. Nonflagellar type III secretion systems (nf T3SSs) form a cell surface needle-like structure and an associated translocon that deliver bacterial effector proteins into eukaryotic host cells. This involves a tightly regulated hierarchy of protein secretion. A switch involving SctP and SctU stops secretion of the needle protein. The gatekeeper protein SctW is required for secretion of translocon proteins and controls a second switch to start effector secretion. Salmonella enterica serovar Typhimurium encodes two T3SSs in Salmonella pathogenicity island 1 (SPI-1) and SPI-2. The acidic vacuole containing intracellular bacteria stimulates assembly of the SPI-2 T3SS and its translocon. Sensing the nearly neutral host cytosolic pH is required for effector translocation. Here, we investigated the involvement of SPI-2-encoded proteins SsaP (SctP), SsaU (SctU), SsaV (SctV), and SsaL (SctW) in regulation of secretion. We found that SsaP and SsaU are involved in the first but not the second secretion switch. A random-mutagenesis screen identified amino acids of SsaV that regulate translocon and effector secretion. Single substitutions in subdomain 4 of SsaV or InvA (SPI-1-encoded SctV) phenocopied mutations of their corresponding gatekeepers with respect to translocon and effector protein secretion and host cell interactions. SsaL interacted with SsaV in bacteria exposed to low ambient pH but not after the pH was raised to 7.2. We propose that SsaP and SsaU enable the apparatus to become competent for a secretion switch and facilitate the SsaL-SsaV interaction. This mediates secretion of translocon proteins until neutral pH is sensed, which causes their dissociation, resulting in arrest of translocon secretion and derepression of effector translocation.
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Novel Role of VisP and the Wzz System during O-Antigen Assembly in Salmonella enterica Serovar Typhimurium Pathogenesis. Infect Immun 2018; 86:IAI.00319-18. [PMID: 29866904 DOI: 10.1128/iai.00319-18] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 05/14/2018] [Indexed: 01/18/2023] Open
Abstract
Salmonella enterica serovars are associated with diarrhea and gastroenteritis and are a helpful model for understanding host-pathogen mechanisms. Salmonella enterica serovar Typhimurium regulates the distribution of O antigen (OAg) and presents a trimodal distribution based on Wzy polymerase and the WzzST (long-chain-length OAg [L-OAg]) and WzzfepE (very-long-chain-length OAg [VL-OAg]) copolymerases; however, several mechanisms regulating this process remain unclear. Here, we report that LPS modifications modulate the infectious process and that OAg chain length determination plays an essential role during infection. An increase in VL-OAg is dependent on Wzy polymerase, which is promoted by a growth condition resembling the environment of Salmonella-containing vacuoles (SCVs). The virulence- and stress-related periplasmic protein (VisP) participates in OAg synthesis, as a ΔvisP mutant presents a semirough OAg phenotype. The ΔvisP mutant has greatly decreased motility and J774 macrophage survival in a colitis model of infection. Interestingly, the phenotype is restored after mutation of the wzzST or wzzfepE gene in a ΔvisP background. Loss of both the visP and wzzST genes promotes an imbalance in flagellin secretion. L-OAg may function as a shield against host immune systems in the beginning of an infectious process, and VL-OAg protects bacteria during SCV maturation and facilitates intramacrophage replication. Taken together, these data highlight the roles of OAg length in generating phenotypes during S Typhimurium pathogenesis and show the periplasmic protein VisP as a novel protein in the OAg biosynthesis pathway.
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do Vale A, Pereira C, Osorio CR, dos Santos NMS. The Apoptogenic Toxin AIP56 Is Secreted by the Type II Secretion System of Photobacterium damselae subsp. piscicida. Toxins (Basel) 2017; 9:toxins9110368. [PMID: 29135911 PMCID: PMC5705983 DOI: 10.3390/toxins9110368] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 11/07/2017] [Accepted: 11/08/2017] [Indexed: 11/16/2022] Open
Abstract
AIP56 (apoptosis-inducing protein of 56 kDa) is a key virulence factor of Photobacterium damselae subsp. piscicida (Phdp), the causative agent of a septicaemia affecting warm water marine fish species. Phdp-associated pathology is triggered by AIP56, a short trip AB toxin with a metalloprotease A domain that cleaves the p65 subunit of NF-κB, an evolutionarily conserved transcription factor that regulates the expression of inflammatory and anti-apoptotic genes and plays a central role in host responses to infection. During infection by Phdp, AIP56 is systemically disseminated and induces apoptosis of macrophages and neutrophils, compromising the host phagocytic defence and contributing to the genesis of pathology. Although it is well established that the secretion of AIP56 is crucial for Phdp pathogenicity, the protein secretion systems operating in Phdp and the mechanism responsible for the extracellular release of the toxin remain unknown. Here, we report that Phdp encodes a type II secretion system (T2SS) and show that mutation of the EpsL component of this system impairs AIP56 secretion. This work demonstrates that Phdp has a functional T2SS that mediates secretion of its key virulence factor AIP56.
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Affiliation(s)
- Ana do Vale
- Fish Immunology and Vaccinology Group, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal.
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-235 Porto, Portugal.
| | - Cassilda Pereira
- Fish Immunology and Vaccinology Group, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal.
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-235 Porto, Portugal.
| | - Carlos R Osorio
- Departamento de Microbioloxía e Parasitoloxía, Instituto de Acuicultura, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain.
| | - Nuno M S dos Santos
- Fish Immunology and Vaccinology Group, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal.
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-235 Porto, Portugal.
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General response of Salmonella enterica serovar Typhimurium to desiccation: A new role for the virulence factors sopD and sseD in survival. PLoS One 2017; 12:e0187692. [PMID: 29117268 PMCID: PMC5678696 DOI: 10.1371/journal.pone.0187692] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 10/10/2017] [Indexed: 02/05/2023] Open
Abstract
Salmonella can survive for long periods under extreme desiccation conditions. This stress tolerance poses a risk for food safety, but relatively little is known about the molecular and cellular regulation of this adaptation mechanism. To determine the genetic components involved in Salmonella’s cellular response to desiccation, we performed a global transcriptomic analysis comparing S. enterica serovar Typhimurium cells equilibrated to low water activity (aw 0.11) and cells equilibrated to high water activity (aw 1.0). The analysis revealed that 719 genes were differentially regulated between the two conditions, of which 290 genes were up-regulated at aw 0.11. Most of these genes were involved in metabolic pathways, transporter regulation, DNA replication/repair, transcription and translation, and, more importantly, virulence genes. Among these, we decided to focus on the role of sopD and sseD. Deletion mutants were created and their ability to survive desiccation and exposure to aw 0.11 was compared to the wild-type strain and to an E. coli O157:H7 strain. The sopD and sseD mutants exhibited significant cell viability reductions of 2.5 and 1.3 Log (CFU/g), respectively, compared to the wild-type after desiccation for 4 days on glass beads. Additional viability differences of the mutants were observed after exposure to aw 0.11 for 7 days. E. coli O157:H7 lost viability similarly to the mutants. Scanning electron microscopy showed that both mutants displayed a different morphology compared to the wild-type and differences in production of the extracellular matrix under the same conditions. These findings suggested that sopD and sseD are required for Salmonella’s survival during desiccation.
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Polar delivery of Legionella type IV secretion system substrates is essential for virulence. Proc Natl Acad Sci U S A 2017; 114:8077-8082. [PMID: 28696299 DOI: 10.1073/pnas.1621438114] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A recurrent emerging theme is the targeting of proteins to subcellular microdomains within bacterial cells, particularly to the poles. In most cases, it has been assumed that this localization is critical to the protein's function. Legionella pneumophila uses a type IVB secretion system (T4BSS) to export a large number of protein substrates into the cytoplasm of host cells. Here we show that the Legionella export apparatus is localized to the bacterial poles, as is consistent with many T4SS substrates being retained on the phagosomal membrane adjacent to the poles of the bacterium. More significantly, we were able to demonstrate that polar secretion of substrates is critically required for Legionella's alteration of the host endocytic pathway, an activity required for this pathogen's virulence.
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Ganesan R, Hos NJ, Gutierrez S, Fischer J, Stepek JM, Daglidu E, Krönke M, Robinson N. Salmonella Typhimurium disrupts Sirt1/AMPK checkpoint control of mTOR to impair autophagy. PLoS Pathog 2017; 13:e1006227. [PMID: 28192515 PMCID: PMC5325604 DOI: 10.1371/journal.ppat.1006227] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 02/24/2017] [Accepted: 02/08/2017] [Indexed: 01/25/2023] Open
Abstract
During intracellular infections, autophagy significantly contributes to the elimination of pathogens, regulation of pro-inflammatory signaling, secretion of immune mediators and in coordinating the adaptive immune system. Intracellular pathogens such as S. Typhimurium have evolved mechanisms to circumvent autophagy. However, the regulatory mechanisms targeted by S. Typhimurium to modulate autophagy have not been fully resolved. Here we report that cytosolic energy loss during S. Typhimurium infection triggers transient activation of AMPK, an important checkpoint of mTOR activity and autophagy. The activation of AMPK is regulated by LKB1 in a cytosolic complex containing Sirt1 and LKB1, where Sirt1 is required for deacetylation and subsequent activation of LKB1. S. Typhimurium infection targets Sirt1, LKB1 and AMPK to lysosomes for rapid degradation resulting in the disruption of the AMPK-mediated regulation of mTOR and autophagy. The degradation of cytosolic Sirt1/LKB1/AMPK complex was not observed with two mutant strains of S. Typhimurium, ΔssrB and ΔssaV, both compromising the pathogenicity island 2 (SPI2). The results highlight virulence factor-dependent degradation of host cell proteins as a previously unrecognized strategy of S. Typhimurium to evade autophagy. S. Typhimurium is a facultative intracellular pathogen which uses its type III secretion system to avoid cell-autonomous defense mechanisms such as autophagy. Here we show that S. Typhimurium induces energy depletion resulting in an early but transient activation of AMPK and autophagy. Salmonella virulence factors target Sirt1/LKB1/AMPK for lysosomal degradation, which enables sustained mTOR-activation and inhibition of autophagy. Activation of mTOR establishes a molecular feedback loop that enhances lysosomal degradation of Sirt1/LKB1/AMPK.
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Affiliation(s)
- Raja Ganesan
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
- Cologne Cluster of Excellence in Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Nina Judith Hos
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
- Cologne Cluster of Excellence in Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
- German Center for Infection Research (DZIF), Cologne, Germany
| | - Saray Gutierrez
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
- Cologne Cluster of Excellence in Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Julia Fischer
- Cologne Cluster of Excellence in Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
- First Department of Internal Medicine, University of Cologne, Cologne, Germany
| | - Joanna Magdalena Stepek
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
- Cologne Cluster of Excellence in Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Evmorphia Daglidu
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
- Cologne Cluster of Excellence in Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Martin Krönke
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
- Cologne Cluster of Excellence in Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
- German Center for Infection Research (DZIF), Cologne, Germany
| | - Nirmal Robinson
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
- Cologne Cluster of Excellence in Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
- * E-mail:
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Yin J, Chen Y, Xie X, Xia J, Li Q, Geng S, Jiao X. Influence of Salmonella enterica serovar Pullorum pathogenicity island 2 on type III secretion system effector gene expression in chicken macrophage HD11 cells. Avian Pathol 2016; 46:209-214. [PMID: 27735192 DOI: 10.1080/03079457.2016.1247432] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Salmonella pathogenicity island 2 (SPI2) can encode type III secretion system 2 (T3SS2) which plays an important role in systemic disease development through delivering different effector proteins into host cells. Here, the influence of Salmonella Pullorum pathogenicity island 2 on T3SS2 effector gene expression was studied using qRT-PCR in chicken macrophage HD11 cells. Our results showed that all the detected genes (including pseudogenes sifB, sspH2 and steC) can express in HD11 cells of S. Pullorum infection; deletion of SPI2 of S. Pullorum did not significantly affect the expression of genes cigR, gtgA, slrP, sopD, sseK1, steB and steC, but had a significant effect on the expression of genes pipB2, sifB, sopD2, sseJ, sseL, sspH2, steD, sifA, pipB and steA at different degrees. These results suggest that SPI2 can significantly affect the expression of some T3SS2 effector genes. Some effectors may have secretion pathways other than T3SS2 and pseudogenes may play roles in the process of S. Pullorum infection.
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Affiliation(s)
- Junlei Yin
- a Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou University , Yangzhou , People's Republic of China
| | - Yun Chen
- a Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou University , Yangzhou , People's Republic of China
| | - Xiaolei Xie
- a Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou University , Yangzhou , People's Republic of China
| | - Jie Xia
- a Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou University , Yangzhou , People's Republic of China
| | - Qiuchun Li
- a Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou University , Yangzhou , People's Republic of China
| | - Shizhong Geng
- a Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou University , Yangzhou , People's Republic of China
| | - Xinan Jiao
- a Jiangsu Key Laboratory of Zoonosis, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou University , Yangzhou , People's Republic of China
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29
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Smith C, Stringer AM, Mao C, Palumbo MJ, Wade JT. Mapping the Regulatory Network for Salmonella enterica Serovar Typhimurium Invasion. mBio 2016; 7:e01024-16. [PMID: 27601571 PMCID: PMC5013294 DOI: 10.1128/mbio.01024-16] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 08/10/2016] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED Salmonella enterica pathogenicity island 1 (SPI-1) encodes proteins required for invasion of gut epithelial cells. The timing of invasion is tightly controlled by a complex regulatory network. The transcription factor (TF) HilD is the master regulator of this process and senses environmental signals associated with invasion. HilD activates transcription of genes within and outside SPI-1, including six other TFs. Thus, the transcriptional program associated with host cell invasion is controlled by at least 7 TFs. However, very few of the regulatory targets are known for these TFs, and the extent of the regulatory network is unclear. In this study, we used complementary genomic approaches to map the direct regulatory targets of all 7 TFs. Our data reveal a highly complex and interconnected network that includes many previously undescribed regulatory targets. Moreover, the network extends well beyond the 7 TFs, due to the inclusion of many additional TFs and noncoding RNAs. By comparing gene expression profiles of regulatory targets for the 7 TFs, we identified many uncharacterized genes that are likely to play direct roles in invasion. We also uncovered cross talk between SPI-1 regulation and other regulatory pathways, which, in turn, identified gene clusters that likely share related functions. Our data are freely available through an intuitive online browser and represent a valuable resource for the bacterial research community. IMPORTANCE Invasion of epithelial cells is an early step during infection by Salmonella enterica and requires secretion of specific proteins into host cells via a type III secretion system (T3SS). Most T3SS-associated proteins required for invasion are encoded in a horizontally acquired genomic locus known as Salmonella pathogenicity island 1 (SPI-1). Multiple regulators respond to environmental signals to ensure appropriate timing of SPI-1 gene expression. In particular, there are seven transcription regulators that are known to be involved in coordinating expression of SPI-1 genes. We have used complementary genome-scale approaches to map the gene targets of these seven regulators. Our data reveal a highly complex and interconnected regulatory network that includes many previously undescribed target genes. Moreover, our data functionally implicate many uncharacterized genes in the invasion process and reveal cross talk between SPI-1 regulation and other regulatory pathways. All datasets are freely available through an intuitive online browser.
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Affiliation(s)
- Carol Smith
- Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Anne M Stringer
- Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Chunhong Mao
- Biocomplexity Institute of Virginia Tech, Virginia Tech, Blacksburg, Virginia, USA
| | - Michael J Palumbo
- Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Joseph T Wade
- Wadsworth Center, New York State Department of Health, Albany, New York, USA Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, USA
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30
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Diepold A, Armitage JP. Type III secretion systems: the bacterial flagellum and the injectisome. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0020. [PMID: 26370933 DOI: 10.1098/rstb.2015.0020] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The flagellum and the injectisome are two of the most complex and fascinating bacterial nanomachines. At their core, they share a type III secretion system (T3SS), a transmembrane export complex that forms the extracellular appendages, the flagellar filament and the injectisome needle. Recent advances, combining structural biology, cryo-electron tomography, molecular genetics, in vivo imaging, bioinformatics and biophysics, have greatly increased our understanding of the T3SS, especially the structure of its transmembrane and cytosolic components, the transcriptional, post-transcriptional and functional regulation and the remarkable adaptivity of the system. This review aims to integrate these new findings into our current knowledge of the evolution, function, regulation and dynamics of the T3SS, and to highlight commonalities and differences between the two systems, as well as their potential applications.
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Affiliation(s)
- Andreas Diepold
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Judith P Armitage
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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31
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Uribe JH, Collado-Romero M, Zaldívar-López S, Arce C, Bautista R, Carvajal A, Cirera S, Claros MG, Garrido JJ. Transcriptional analysis of porcine intestinal mucosa infected with Salmonella Typhimurium revealed a massive inflammatory response and disruption of bile acid absorption in ileum. Vet Res 2016; 47:11. [PMID: 26738723 PMCID: PMC4704413 DOI: 10.1186/s13567-015-0286-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 11/13/2015] [Indexed: 01/16/2023] Open
Abstract
Infected pork meat is an important source of non-typhoidal human salmonellosis. Understanding of molecular mechanisms involved in disease pathogenesis is important for the development of therapeutic and preventive strategies. Thus, hereby we study the transcriptional profiles along the porcine intestine during infection with Salmonella Typhimurium, as well as post-transcriptional gene modulation by microRNAs (miRNA). Sixteen piglets were orally challenged with S. Typhimurium. Samples from jejunum, ileum and colon, collected 1, 2 and 6 days post infection (dpi) were hybridized to mRNA and miRNA expression microarrays and analyzed. Jejunum showed a reduced transcriptional response indicating mild inflammation only at 2 dpi. In ileum inflammatory genes were overexpressed (e.g., IL-1B, IL-6, IL-8, IL1RAP, TNFα), indicating a strong immune response at all times of infection. Infection also down-regulated genes of the FXR pathway (e.g., NR1H4, FABP6, APOA1, SLC10A2), indicating disruption of the bile acid absorption in ileum. This result was confirmed by decreased high-density lipoprotein cholesterol in serum of infected pigs. Ileal inflammatory gene expression changes peaked at 2 dpi and tended to resolve at 6 dpi. Furthermore, miRNA analysis of ileum at 2 dpi revealed 62 miRNAs potentially regulating target genes involved in this inflammatory process (e.g., miR-374 and miR-451). In colon, genes involved in epithelial adherence, proliferation and cellular reorganization were down-regulated at 2 and 6 dpi. In summary, here we show the transcriptional changes occurring at the intestine at different time points of the infection, which are mainly related to inflammation and disruption of the bile acid metabolism.
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Affiliation(s)
- Juber Herrera Uribe
- Grupo de Genómica y Mejora Animal, Departamento de Genética, Facultad de Veterinaria, Universidad de Córdoba, 14047, Córdoba, Spain.
| | - Melania Collado-Romero
- Grupo de Genómica y Mejora Animal, Departamento de Genética, Facultad de Veterinaria, Universidad de Córdoba, 14047, Córdoba, Spain.
| | - Sara Zaldívar-López
- Grupo de Genómica y Mejora Animal, Departamento de Genética, Facultad de Veterinaria, Universidad de Córdoba, 14047, Córdoba, Spain.
| | - Cristina Arce
- Departamento de Producción Animal, Facultad de Veterinaria, Universidad de Córdoba, 14047, Córdoba, Spain.
| | - Rocío Bautista
- Plataforma Andaluza de Bioinformática, Universidad de Málaga, 29590, Málaga, Spain.
| | - Ana Carvajal
- Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad de León, 24071, León, Spain.
| | - Susanna Cirera
- Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 1870, Copenhagen, Denmark.
| | - M Gonzalo Claros
- Plataforma Andaluza de Bioinformática, Universidad de Málaga, 29590, Málaga, Spain.
- Departamento de Biología Molecular y Bioquímica, Universidad de Málaga, 29071, Málaga, Spain.
| | - Juan J Garrido
- Grupo de Genómica y Mejora Animal, Departamento de Genética, Facultad de Veterinaria, Universidad de Córdoba, 14047, Córdoba, Spain.
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Chakraborty S, Mizusaki H, Kenney LJ. A FRET-based DNA biosensor tracks OmpR-dependent acidification of Salmonella during macrophage infection. PLoS Biol 2015; 13:e1002116. [PMID: 25875623 PMCID: PMC4397060 DOI: 10.1371/journal.pbio.1002116] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 02/24/2015] [Indexed: 11/19/2022] Open
Abstract
In bacteria, one paradigm for signal transduction is the two-component regulatory system, consisting of a sensor kinase (usually a membrane protein) and a response regulator (usually a DNA binding protein). The EnvZ/OmpR two-component system responds to osmotic stress and regulates expression of outer membrane proteins. In Salmonella, EnvZ/OmpR also controls expression of another two-component system SsrA/B, which is located on Salmonella Pathogenicity Island (SPI) 2. SPI-2 encodes a type III secretion system, which functions as a nanomachine to inject bacterial effector proteins into eukaryotic cells. During the intracellular phase of infection, Salmonella switches from assembling type III secretion system structural components to secreting effectors into the macrophage cytoplasm, enabling Salmonella to replicate in the phagocytic vacuole. Major questions remain regarding how bacteria survive the acidified vacuole and how acidification affects bacterial secretion. We previously reported that EnvZ sensed cytoplasmic signals rather than extracellular ones, as intracellular osmolytes altered the dynamics of a 17-amino-acid region flanking the phosphorylated histidine. We reasoned that the Salmonella cytoplasm might acidify in the macrophage vacuole to activate OmpR-dependent transcription of SPI-2 genes. To address these questions, we employed a DNA-based FRET biosensor ("I-switch") to measure bacterial cytoplasmic pH and immunofluorescence to monitor effector secretion during infection. Surprisingly, we observed a rapid drop in bacterial cytoplasmic pH upon phagocytosis that was not predicted by current models. Cytoplasmic acidification was completely dependent on the OmpR response regulator, but did not require known OmpR-regulated genes such as ompC, ompF, or ssaC (SPI-2). Microarray analysis highlighted the cadC/BA operon, and additional experiments confirmed that it was repressed by OmpR. Acidification was blocked in the ompR null background in a Cad-dependent manner. Acid-dependent activation of OmpR stimulated type III secretion; blocking acidification resulted in a neutralized cytoplasm that was defective for SPI-2 secretion. Based upon these findings, we propose that Salmonella infection involves an acid-dependent secretion process in which the translocon SseB moves away from the bacterial cell surface as it associates with the vacuolar membrane, driving the secretion of SPI-2 effectors such as SseJ. New steps in the SPI-2 secretion process are proposed.
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Affiliation(s)
| | - Hideaki Mizusaki
- Mechanobiology Institute, National University of Singapore, Singapore
| | - Linda J. Kenney
- Mechanobiology Institute, National University of Singapore, Singapore
- Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois, United States of America
- Department of Microbiology and Immunology, University of Illinois-Chicago, Chicago, Illinois, United States of America
- * E-mail:
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Kolodziejek AM, Miller SI. Salmonella modulation of the phagosome membrane, role of SseJ. Cell Microbiol 2015; 17:333-41. [PMID: 25620407 DOI: 10.1111/cmi.12420] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 01/21/2015] [Accepted: 01/22/2015] [Indexed: 12/15/2022]
Abstract
Salmonellae have the ability to invade, persist and replicate within an intracellular phagosome termed the Salmonella-containing vacuole (SCV). Salmonellae alter lipid and protein content of the SCV membrane and manipulate cytoskeletal elements in contact with the SCV using the Salmonella pathogenicity island 1 (SPI-2) type III secretion system effectors. These modifications result in microtubular-based movement and morphological changes, which include endosomal tubulation of the SCV membrane. SseJ is a SPI-2 effector that localizes to the cytoplasmic face of the SCV and esterifies cholesterol through its glycerophospholipid : cholesterol acyltransferase activity. SseJ enzymatic activity as well as localization to the SCV are determined by binding to the small mammalian GTPase, RhoA. This review will focus on current knowledge about the role of SseJ in SCV membrane modification and will discuss how the hypothesis that a major role of SPI-2 effectors is to modify SCV protein and lipid content to promote bacterial intracellular survival.
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McWhorter AR, Chousalkar KK. Comparative phenotypic and genotypic virulence of Salmonella strains isolated from Australian layer farms. Front Microbiol 2015; 6:12. [PMID: 25667583 PMCID: PMC4304256 DOI: 10.3389/fmicb.2015.00012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 01/06/2015] [Indexed: 11/23/2022] Open
Abstract
There are over 2500 Salmonella enterica serovars that circulate globally. Of these, serovars those classified into subspecies I are the most common cause of human salmonellosis. Many subspecies I Salmonella serovars are routinely isolated from egg farm environments but are not frequently associated with causing disease in humans. In this study, virulence profiles were generated for 10 strains of Salmonella enterica isolated directly from egg farm environments to investigate their potential public health risk. Three virulence parameters were assessed including in vitro invasion, in vivo pathogenicity and characterization of genomic variation within five specific pathogenicity islands. These 10 Salmonella strains exhibited significant differences in invasion into the human intestinal epithelial cell line, Caco2. Low, moderate, and high invasion patterns were observed and the degree of invasion was dependent on bacterial growth in a nutritive environment. Interestingly, two Salmonella strains, S. Adelaide and S. Bredeney had consistently low invasion. The S. Typhimurium definitive types and S. Virchow exhibited the greatest cell invasion following growth in Luria Bertani broth. Only the S. Typhimurium strains caused disease in BALB/c mice, yet the majority of serovars were consistently detected in feces over the 21 day experiment. Genomic comparison of the five specific pathogenicity islands has shown that variation in virulence is likely multifactorial. Sequence variability was observed primarily in strains with low virulence. In particular, genes involved in forming the structures of the SPI-1 and SPI-2 type 3 secretion systems as well as multiple effector proteins were among the most variable. This variability suggest that serovars with low virulence are likely to have both invasion and within host replication defects that ultimately limit their pathogenicity.
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Affiliation(s)
- Andrea R McWhorter
- School of Animal and Veterinary Sciences, University of Adelaide - Roseworthy Campus Roseworthy, SA, Australia
| | - Kapil K Chousalkar
- School of Animal and Veterinary Sciences, University of Adelaide - Roseworthy Campus Roseworthy, SA, Australia
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Egan F, Barret M, O’Gara F. The SPI-1-like Type III secretion system: more roles than you think. FRONTIERS IN PLANT SCIENCE 2014; 5:34. [PMID: 24575107 PMCID: PMC3921676 DOI: 10.3389/fpls.2014.00034] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 01/25/2014] [Indexed: 05/05/2023]
Abstract
The type III secretion system (T3SS) is a protein delivery system which is involved in a wide spectrum of interactions, from mutualism to pathogenesis, between Gram negative bacteria and various eukaryotes, including plants, fungi, protozoa and mammals. Various phylogenetic families of the T3SS have been described, including the Salmonella Pathogenicity Island 1 family (SPI-1). The SPI-1 T3SS was initially associated with the virulence of enteric pathogens, but is actually found in a diverse array of bacterial species, where it can play roles in processes as different as symbiotic interactions with insects and colonization of plants. We review the multiple roles of the SPI-1 T3SS and discuss both how these discoveries are changing our perception of the SPI-1 family and what impacts this has on our understanding of the specialization of the T3SS in general.
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Affiliation(s)
- Frank Egan
- BIOMERIT Research Centre, School of Microbiology, University College CorkCork, Ireland
| | - Matthieu Barret
- UMR1345 Institut de Recherche en Horticulture et Semences, Institut National de la Recherche AgronomiqueBeaucouzé, France
- UMR1345 Institut de Recherches en Horticulture et SemencesAgrocampus Ouest, Beaucouzé, France
- Université d’Angers, UMR1345 Institut de Recherches en Horticulture et Semences, SFR4207 QUASAVBeaucouzé, France
| | - Fergal O’Gara
- BIOMERIT Research Centre, School of Microbiology, University College CorkCork, Ireland
- School of Biomedical Sciences, Curtin UniversityPerth, WA, Australia
- *Correspondence: Fergal O’Gara, BIOMERIT Research Centre, School of Microbiology, University College Cork, Cork, Ireland e-mail:
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Remuzgo-Martínez S, Aranzamendi-Zaldunbide M, Pilares-Ortega L, Icardo JM, Acosta F, Martínez-Martínez L, Ramos-Vivas J. Interaction of macrophages with a cytotoxic Serratia liquefaciens human isolate. Microbes Infect 2013; 15:480-90. [PMID: 23524146 DOI: 10.1016/j.micinf.2013.03.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 03/07/2013] [Accepted: 03/11/2013] [Indexed: 11/18/2022]
Abstract
Macrophages play key roles in host defense by recognizing, engulfing, and killing microorganisms. Understanding the response of macrophages to pathogens may provide insights into host defenses and the tactics used by pathogens to circumvent these defenses. In the present study, we investigated the interaction between a clinical isolate of Serratia liquefaciens and macrophages. S. liquefaciens strain HUMV-3250 triggers a fast and potent cytotoxic effect upon infection. This process requires the presence of live bacteria, adherence, and protein synthesis but not phagocytosis/bacterial internalization. Moreover, cytotoxicity assays, analysis of DNA integrity, immunofluorescence, and confocal, scanning, and time-lapse microscopy revealed that macrophage viability decreased rapidly with time upon challenge, and depends on the MOI used. Treatment of macrophages with caspase-1 inhibitors, or with specific inhibitors of phagocytosis, did not alter the infection outcome. Moreover, human macrophages exhibited similar cytotoxic changes after infection with this strain. Macrophages responded to this cytotoxic strain with a robust pattern of pro-inflammatory gene expression. However, phagocytosis attempts to engulf live bacteria were unsuccessful, and the phagocytes were unable to kill the bacteria. We conclude that macrophage cell death occurs rapidly as a result of necrotic events after close contact with S. liquefaciens. These results likely have important implications for understanding Serratia pathogenesis and host response to infection.
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Affiliation(s)
- Sara Remuzgo-Martínez
- Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla-IFIMAV, Santander, Cantabria, Spain
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Dehghani B, Rasooli I, Gargari SLM, Nadooshan MRJ, Owlia P, Nazarian S. Immunogenicity of Salmonella enterica serovar Enteritidis virulence protein, InvH, and cross-reactivity of its antisera with Salmonella strains. Microbiol Res 2013; 168:84-90. [PMID: 23141708 DOI: 10.1016/j.micres.2012.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 09/03/2012] [Accepted: 09/09/2012] [Indexed: 11/19/2022]
Affiliation(s)
- Behzad Dehghani
- Department of Biology, Shahed University, Tehran-Qom Express Way, Opposite Imam Khomeini's Shrine, Tehran 3319118651, Iran
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Moest TP, Méresse S. Salmonella T3SSs: successful mission of the secret(ion) agents. Curr Opin Microbiol 2013; 16:38-44. [DOI: 10.1016/j.mib.2012.11.006] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 11/15/2012] [Accepted: 11/26/2012] [Indexed: 10/27/2022]
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The type VI secretion system encoded in Salmonella pathogenicity island 19 is required for Salmonella enterica serotype Gallinarum survival within infected macrophages. Infect Immun 2013; 81:1207-20. [PMID: 23357385 DOI: 10.1128/iai.01165-12] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Salmonella enterica serotype Gallinarum is the causative agent of fowl typhoid, a disease characterized by high morbidity and mortality that causes major economic losses in poultry production. We have reported that S. Gallinarum harbors a type VI secretion system (T6SS) encoded in Salmonella pathogenicity island 19 (SPI-19) that is required for efficient colonization of chicks. In the present study, we aimed to characterize the SPI-19 T6SS functionality and to investigate the mechanisms behind the phenotypes previously observed in vivo. Expression analyses revealed that SPI-19 T6SS core components are expressed and produced under in vitro bacterial growth conditions. However, secretion of the structural/secreted components Hcp1, Hcp2, and VgrG to the culture medium could not be determined, suggesting that additional signals are required for T6SS-dependent secretion of these proteins. In vitro bacterial competition assays failed to demonstrate a role for SPI-19 T6SS in interbacterial killing. In contrast, cell culture experiments with murine and avian macrophages (RAW264.7 and HD11, respectively) revealed production of a green fluorescent protein-tagged version of VgrG soon after Salmonella uptake. Furthermore, infection of RAW264.7 and HD11 macrophages with deletion mutants of SPI-19 or strains with genes encoding specific T6SS core components (clpV and vgrG) revealed that SPI-19 T6SS contributes to S. Gallinarum survival within macrophages at 20 h postuptake. SPI-19 T6SS function was not linked to Salmonella-induced cytotoxicity or cell death of infected macrophages, as has been described for other T6SS. Our data indicate that SPI-19 T6SS corresponds to a novel tool used by Salmonella to survive within host cells.
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Grant AJ, Morgan FJE, McKinley TJ, Foster GL, Maskell DJ, Mastroeni P. Attenuated Salmonella Typhimurium lacking the pathogenicity island-2 type 3 secretion system grow to high bacterial numbers inside phagocytes in mice. PLoS Pathog 2012; 8:e1003070. [PMID: 23236281 PMCID: PMC3516571 DOI: 10.1371/journal.ppat.1003070] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 10/19/2012] [Indexed: 01/23/2023] Open
Abstract
Intracellular replication within specialized vacuoles and cell-to-cell spread in the tissue are essential for the virulence of Salmonella enterica. By observing infection dynamics at the single-cell level in vivo, we have discovered that the Salmonella pathogenicity island 2 (SPI-2) type 3 secretory system (T3SS) is dispensable for growth to high intracellular densities. This challenges the concept that intracellular replication absolutely requires proteins delivered by SPI-2 T3SS, which has been derived largely by inference from in vitro cell experiments and from unrefined measurement of net growth in mouse organs. Furthermore, we infer from our data that the SPI-2 T3SS mediates exit from infected cells, with consequent formation of new infection foci resulting in bacterial spread in the tissues. This suggests a new role for SPI-2 in vivo as a mediator of bacterial spread in the body. In addition, we demonstrate that very similar net growth rates of attenuated salmonellae in organs can be derived from very different underlying intracellular growth dynamics.
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Affiliation(s)
- Andrew J Grant
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.
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Protein export according to schedule: architecture, assembly, and regulation of type III secretion systems from plant- and animal-pathogenic bacteria. Microbiol Mol Biol Rev 2012; 76:262-310. [PMID: 22688814 DOI: 10.1128/mmbr.05017-11] [Citation(s) in RCA: 312] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Flagellar and translocation-associated type III secretion (T3S) systems are present in most gram-negative plant- and animal-pathogenic bacteria and are often essential for bacterial motility or pathogenicity. The architectures of the complex membrane-spanning secretion apparatuses of both systems are similar, but they are associated with different extracellular appendages, including the flagellar hook and filament or the needle/pilus structures of translocation-associated T3S systems. The needle/pilus is connected to a bacterial translocon that is inserted into the host plasma membrane and mediates the transkingdom transport of bacterial effector proteins into eukaryotic cells. During the last 3 to 5 years, significant progress has been made in the characterization of membrane-associated core components and extracellular structures of T3S systems. Furthermore, transcriptional and posttranscriptional regulators that control T3S gene expression and substrate specificity have been described. Given the architecture of the T3S system, it is assumed that extracellular components of the secretion apparatus are secreted prior to effector proteins, suggesting that there is a hierarchy in T3S. The aim of this review is to summarize our current knowledge of T3S system components and associated control proteins from both plant- and animal-pathogenic bacteria.
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Figueira R, Holden DW. Functions of the Salmonella pathogenicity island 2 (SPI-2) type III secretion system effectors. Microbiology (Reading) 2012; 158:1147-1161. [DOI: 10.1099/mic.0.058115-0] [Citation(s) in RCA: 253] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Affiliation(s)
- Rita Figueira
- Section of Microbiology, Centre for Molecular Microbiology and Infection, Imperial College London, Armstrong Road, London SW7 2AZ, UK
| | - David W. Holden
- Section of Microbiology, Centre for Molecular Microbiology and Infection, Imperial College London, Armstrong Road, London SW7 2AZ, UK
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Li G, Young KD. Isolation and identification of new inner membrane-associated proteins that localize to cell poles inEscherichia coli. Mol Microbiol 2012; 84:276-95. [DOI: 10.1111/j.1365-2958.2012.08021.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Jennings ME, Quick LN, Ubol N, Shrom S, Dollahon N, Wilson JW. Characterization of Salmonella type III secretion hyper-activity which results in biofilm-like cell aggregation. PLoS One 2012; 7:e33080. [PMID: 22412985 PMCID: PMC3297627 DOI: 10.1371/journal.pone.0033080] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 02/07/2012] [Indexed: 01/06/2023] Open
Abstract
We have previously reported the cloning of the Salmonella enterica serovar Typhimurium SPI-1 secretion system and the use of this clone to functionally complement a ΔSPI-1 strain for type III secretion activity. In the current study, we discovered that S. Typhimurium cultures containing cloned SPI-1 display an adherent biofilm and cell clumps in the media. This phenotype was associated with hyper-expression of SPI-1 type III secretion functions. The biofilm and cell clumps were associated with copious amounts of secreted SPI-1 protein substrates SipA, SipB, SipC, SopB, SopE, and SptP. We used a C-terminally FLAG-tagged SipA protein to further demonstrate SPI-1 substrate association with the cell aggregates using fluorescence microscopy and immunogold electron microscopy. Different S. Typhimurium backgrounds and both flagellated and nonflagellated strains displayed the biofilm phenotype. Mutations in genes essential for known bacterial biofilm pathways (bcsA, csgBA, bapA) did not affect the biofilms formed here indicating that this phenomenon is independent of established biofilm mechanisms. The SPI-1-mediated biofilm was able to massively recruit heterologous non-biofilm forming bacteria into the adherent cell community. The results indicate a bacterial aggregation phenotype mediated by elevated SPI-1 type III secretion activity with applications for engineered biofilm formation, protein purification strategies, and antigen display.
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Affiliation(s)
- Matthew E. Jennings
- Department of Biology, Villanova University, Villanova, Pennsylvania, United States of America
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, United States of America
| | - Laura N. Quick
- Department of Biology, Villanova University, Villanova, Pennsylvania, United States of America
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Nicha Ubol
- Department of Biology, Villanova University, Villanova, Pennsylvania, United States of America
| | - Sally Shrom
- Department of Biology, Villanova University, Villanova, Pennsylvania, United States of America
| | - Norman Dollahon
- Department of Biology, Villanova University, Villanova, Pennsylvania, United States of America
| | - James W. Wilson
- Department of Biology, Villanova University, Villanova, Pennsylvania, United States of America
- * E-mail:
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Allam US, Krishna MG, Sen M, Thomas R, Lahiri A, Gnanadhas DP, Chakravortty D. Acidic pH induced STM1485 gene is essential for intracellular replication of Salmonella. Virulence 2012; 3:122-135. [PMID: 22460643 PMCID: PMC3396692 DOI: 10.4161/viru.19029] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
During the course of infection, Salmonella has to face several potentially lethal environmental conditions, one such being acidic pH. The ability to sense and respond to the acidic pH is crucial for the survival and replication of Salmonella. The physiological role of one gene (STM1485) involved in this response, which is upregulated inside the host cells (by 90- to 113-fold) is functionally characterized in Salmonella pathogenesis. In vitro, the ΔSTM1485 neither exhibited any growth defect at pH 4.5 nor any difference in the acid tolerance response. The ΔSTM1485 was compromised in its capacity to proliferate inside the host cells and complementation with STM1485 gene restored its virulence. We further demonstrate that the surface translocation of Salmonella pathogenicity island-2 (SPI-2) encoded translocon proteins, SseB and SseD were reduced in the ΔSTM1485. The increase in co-localization of this mutant with lysosomes was also observed. In addition, the ΔSTM1485 displayed significantly reduced competitive indices (CI) in spleen, liver and mesenteric lymph nodes in murine typhoid model when infected by intra-gastric route. Based on these results, we conclude that the acidic pH induced STM1485 gene is essential for intracellular replication of Salmonella.
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Affiliation(s)
| | | | - Minakshi Sen
- Department of Microbiology and Cell Biology; Centre for Infectious Disease Research and Biosafety Laboratories; Indian Institute of Science; Bangalore, India
| | - Rony Thomas
- Department of Microbiology and Cell Biology; Centre for Infectious Disease Research and Biosafety Laboratories; Indian Institute of Science; Bangalore, India
| | - Amit Lahiri
- Department of Microbiology and Cell Biology; Centre for Infectious Disease Research and Biosafety Laboratories; Indian Institute of Science; Bangalore, India
| | - Divya Prakash Gnanadhas
- Department of Microbiology and Cell Biology; Centre for Infectious Disease Research and Biosafety Laboratories; Indian Institute of Science; Bangalore, India
| | - Dipshikha Chakravortty
- Department of Microbiology and Cell Biology; Centre for Infectious Disease Research and Biosafety Laboratories; Indian Institute of Science; Bangalore, India
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A review of the ecology, colonization and genetic characterization of Salmonella enterica serovar Sofia, a prolific but avirulent poultry serovar in Australia. Food Res Int 2012. [DOI: 10.1016/j.foodres.2011.04.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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47
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Bulmer DM, Kharraz L, Grant AJ, Dean P, Morgan FJE, Karavolos MH, Doble AC, McGhie EJ, Koronakis V, Daniel RA, Mastroeni P, Anjam Khan CM. The bacterial cytoskeleton modulates motility, type 3 secretion, and colonization in Salmonella. PLoS Pathog 2012; 8:e1002500. [PMID: 22291596 PMCID: PMC3266929 DOI: 10.1371/journal.ppat.1002500] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Accepted: 12/07/2011] [Indexed: 11/26/2022] Open
Abstract
Although there have been great advances in our understanding of the bacterial cytoskeleton, major gaps remain in our knowledge of its importance to virulence. In this study we have explored the contribution of the bacterial cytoskeleton to the ability of Salmonella to express and assemble virulence factors and cause disease. The bacterial actin-like protein MreB polymerises into helical filaments and interacts with other cytoskeletal elements including MreC to control cell-shape. As mreB appears to be an essential gene, we have constructed a viable ΔmreC depletion mutant in Salmonella. Using a broad range of independent biochemical, fluorescence and phenotypic screens we provide evidence that the Salmonella pathogenicity island-1 type three secretion system (SPI1-T3SS) and flagella systems are down-regulated in the absence of MreC. In contrast the SPI-2 T3SS appears to remain functional. The phenotypes have been further validated using a chemical genetic approach to disrupt the functionality of MreB. Although the fitness of ΔmreC is reduced in vivo, we observed that this defect does not completely abrogate the ability of Salmonella to cause disease systemically. By forcing on expression of flagella and SPI-1 T3SS in trans with the master regulators FlhDC and HilA, it is clear that the cytoskeleton is dispensable for the assembly of these structures but essential for their expression. As two-component systems are involved in sensing and adapting to environmental and cell surface signals, we have constructed and screened a panel of such mutants and identified the sensor kinase RcsC as a key phenotypic regulator in ΔmreC. Further genetic analysis revealed the importance of the Rcs two-component system in modulating the expression of these virulence factors. Collectively, these results suggest that expression of virulence genes might be directly coordinated with cytoskeletal integrity, and this regulation is mediated by the two-component system sensor kinase RcsC. Salmonella are major global pathogens responsible for causing food-borne disease. In recent years the existence of a cytoskeleton in prokaryotes has received much attention. In this study the Salmonella cytoskeleton has been genetically disrupted, causing changes in morphology, motility and expression of key virulence factors. We provide evidence that the sensory protein RcsC detects changes at the cell surface caused by the disintegration of the bacterial cytoskeleton and modulates expression of key virulence factors. This study provides insights into the importance of the integrity of the bacterial cytoskeleton in the ability of Salmonella to cause disease, and thus may provide a novel target for antimicrobial drugs or vaccines.
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Affiliation(s)
- David M. Bulmer
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Newcastle, United Kingdom
| | - Lubna Kharraz
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Newcastle, United Kingdom
| | - Andrew J. Grant
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Paul Dean
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Newcastle, United Kingdom
| | - Fiona J. E. Morgan
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Michail H. Karavolos
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Newcastle, United Kingdom
| | - Anne C. Doble
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Newcastle, United Kingdom
| | - Emma J. McGhie
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Vassilis Koronakis
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Richard A. Daniel
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Newcastle, United Kingdom
| | - Pietro Mastroeni
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - C. M. Anjam Khan
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Newcastle, United Kingdom
- * E-mail:
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48
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Wisner ALS, Potter AA, Köster W. Effect of the Salmonella pathogenicity island 2 type III secretion system on Salmonella survival in activated chicken macrophage-like HD11 cells. PLoS One 2011; 6:e29787. [PMID: 22216355 PMCID: PMC3246499 DOI: 10.1371/journal.pone.0029787] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 12/05/2011] [Indexed: 11/18/2022] Open
Abstract
In order to better identify the role of the Salmonella pathogenicity island 2 (SPI-2) type III secretion system (T3SS) in chickens, we used the well-known gentamicin protection assay with activated HD11 cells. HD11 cells are a macrophage-like chicken cell line that can be stimulated with phorbol 12-myristate 13-acetate (PMA) to exhibit more macrophage-like morphology and greater production of reactive oxygen species (ROS). Activated HD11 cells were infected with a wild-type Salmonella enterica subspecies enterica serovar Typhimurium (S. Typhimurium) strain, a SPI-2 mutant S. Typhimurium strain, a wild-type Salmonella enterica subspecies enterica serovar Enteritidis (S. Enteritidis) strain, a SPI-2 mutant S. Enteritidis strain, or a non-pathogenic Escherichia coli (E. coli) strain. SPI-2 mutant strains were found to survive as well as their parent strain at all time points post-uptake (PU) by the HD11 cells, up to 24 h PU, while the E. coli strain was no longer recoverable by 3 h PU. We can conclude from these observations that the SPI-2 T3SS of S. Typhimurium and S. Enteritidis is not important for survival of Salmonella in the activated macrophage-like HD11 cell line, and that Salmonella must employ other mechanisms for survival in this environment, as E. coli is effectively eliminated.
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Affiliation(s)
- Amanda L. S. Wisner
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Canada
- Canadian Center for Vaccinology, Izaak Walton Killam Health Centre, Halifax, Canada
| | - Andrew A. Potter
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Canada
| | - Wolfgang Köster
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Canada
- * E-mail:
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Yu XJ, Liu M, Matthews S, Holden DW. Tandem translation generates a chaperone for the Salmonella type III secretion system protein SsaQ. J Biol Chem 2011; 286:36098-36107. [PMID: 21878641 PMCID: PMC3195561 DOI: 10.1074/jbc.m111.278663] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Type III secretion systems (T3SSs) of bacterial pathogens involve the assembly of a surface-localized needle complex, through which translocon proteins are secreted to form a pore in the eukaryotic cell membrane. This enables the transfer of effector proteins from the bacterial cytoplasm to the host cell. A structure known as the C-ring is thought to have a crucial role in secretion by acting as a cytoplasmic sorting platform at the base of the T3SS. Here, we studied SsaQ, an FliN-like putative C-ring protein of the Salmonella pathogenicity island 2 (SPI-2)-encoded T3SS. ssaQ produces two proteins by tandem translation: a long form (SsaQ(L)) composed of 322 amino acids and a shorter protein (SsaQ(S)) comprising the C-terminal 106 residues of SsaQ(L). SsaQ(L) is essential for SPI-2 T3SS function. Loss of SsaQ(S) impairs the function of the T3SS both ex vivo and in vivo. SsaQ(S) binds to its corresponding region within SsaQ(L) and stabilizes the larger protein. Therefore, SsaQ(L) function is optimized by a novel chaperone-like protein, produced by tandem translation from its own mRNA species.
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Affiliation(s)
- Xiu-Jun Yu
- Section of Microbiology, Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, United Kingdom
| | - Mei Liu
- Section of Microbiology, Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, United Kingdom
| | - Steve Matthews
- Division of Molecular Biosciences, Centre for Structural Biology, Imperial College London, London SW7 2AZ, United Kingdom
| | - David W Holden
- Section of Microbiology, Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, United Kingdom.
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Krzymińska S, Mokracka J, Koczura R, Cwiertnia A, Kaznowski A. Aeromonas spp.-mediated cell-contact cytotoxicity is associated with the presence of type III secretion system. Antonie van Leeuwenhoek 2011; 101:243-51. [PMID: 21809027 PMCID: PMC3261397 DOI: 10.1007/s10482-011-9627-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Accepted: 07/20/2011] [Indexed: 11/28/2022]
Abstract
In the study we examined the production of cytotonic and cytotoxic toxins and the presence of a type III secretion system (TTSS) in 64 Aeromonas spp. strains isolated from fecal specimens of patients with gastroenteritis. We observed that contact of the bacteria with host epithelial cells is a prerequisite for their cytotoxicity at 3 h incubation. Cell-contact cytotoxic activity of the strains was strongly associated with the presence of the TTSS. Culture supernatants of the strains induced low cytotoxicity effects at the same time of incubation. Cell-free supernatants of 61 (95%) isolates expressed cytotoxic activity which caused the destruction of HEp-2 cells at 24 h. Moreover, 44% strains were cytotonic towards CHO cells and 46% of strains invaded epithelial cells.
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Affiliation(s)
- Sylwia Krzymińska
- Department of Microbiology, Faculty of Biology A. Mickiewicz University, 61-614 Poznań, ul. Umultowska 89, Poznan, Poland.
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