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Crosby HA, Keim K, Kwiecinski JM, Langouët-Astrié CJ, Oshima K, LaRivière WB, Schmidt EP, Horswill AR. Host-derived protease promotes aggregation of Staphylococcus aureus by cleaving the surface protein SasG. mBio 2024; 15:e0348323. [PMID: 38511930 PMCID: PMC11005337 DOI: 10.1128/mbio.03483-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 02/21/2024] [Indexed: 03/22/2024] Open
Abstract
Staphylococcus aureus is one of the leading causes of hospital-acquired infections, many of which begin following attachment and accumulation on indwelling medical devices or diseased tissue. These infections are often linked to the establishment of biofilms, but another often overlooked key characteristic allowing S. aureus to establish persistent infection is the formation of planktonic aggregates. Such aggregates are physiologically similar to biofilms and protect pathogens from innate immune clearance and increase antibiotic tolerance. The cell-wall-associated protein SasG has been implicated in biofilm formation via mechanisms of intercellular aggregation but the mechanism in the context of disease is largely unknown. We have previously shown that the expression of cell-wall-anchored proteins involved in biofilm formation is controlled by the ArlRS-MgrA regulatory cascade. In this work, we demonstrate that the ArlRS two-component system controls aggregation, by repressing the expression of sasG by activation of the global regulator MgrA. We also demonstrate that SasG must be proteolytically processed by a non-staphylococcal protease to induce aggregation and that strains expressing functional full-length sasG aggregate significantly upon proteolysis by a mucosal-derived host protease found in human saliva. We used fractionation and N-terminal sequencing to demonstrate that human trypsin within saliva cleaves within the A domain of SasG to expose the B domain and induce aggregation. Finally, we demonstrated that SasG is involved in virulence during mouse lung infection. Together, our data point to SasG, its processing by host proteases, and SasG-driven aggregation as important elements of S. aureus adaptation to the host environment.IMPORTANCEHere, we demonstrate that the Staphylococcus aureus surface protein SasG is important for cell-cell aggregation in the presence of host proteases. We show that the ArlRS two-component regulatory system controls SasG levels through the cytoplasmic regulator MgrA. We identified human trypsin as the dominant protease triggering SasG-dependent aggregation and demonstrated that SasG is important for S. aureus lung infection. The discovery that host proteases can induce S. aureus aggregation contributes to our understanding of how this pathogen establishes persistent infections. The observations in this study demonstrate the need to strengthen our knowledge of S. aureus surface adhesin function and processing, regulation of adhesin expression, and the mechanisms that promote biofilm formation to develop strategies for preventing chronic infections.
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Affiliation(s)
- Heidi A. Crosby
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Klara Keim
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Jakub M. Kwiecinski
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
- Department of Microbiology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland
| | - Christophe J. Langouët-Astrié
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Kaori Oshima
- Division of Pulmonary Sciences and Critical Care, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Wells B. LaRivière
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Eric P. Schmidt
- Division of Pulmonary Sciences and Critical Care, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Alexander R. Horswill
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
- Department of Veterans Affairs Eastern Colorado Health Care System, Denver, Colorado, USA
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2
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Costa FG, Mills KB, Crosby HA, Horswill AR. The Staphylococcus aureus regulatory program in a human skin-like environment. mBio 2024:e0045324. [PMID: 38546267 DOI: 10.1128/mbio.00453-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 03/04/2024] [Indexed: 04/09/2024] Open
Abstract
Staphylococcus aureus is a Gram-positive pathogen responsible for the majority of skin and soft tissue infections (SSTIs). S. aureus colonizes the anterior nares of approximately 20%-30% of the population and transiently colonizes the skin, thereby increasing the risk of developing SSTIs and more serious infections. Current laboratory models that mimic the skin surface environment are expensive, require substantial infrastructure, and limit the scope of bacterial physiology studies under human skin conditions. To overcome these limitations, we developed a cost-effective, open-source, chemically defined media recipe termed skin-like medium (SLM) that incorporates key aspects of the human skin surface environment and supports growth of several staphylococcal species. We utilized SLM to investigate the transcriptional response of methicillin-resistant Staphylococcus aureus (MRSA) following growth in SLM compared to a commonly used laboratory media. Through RNA-seq analysis, we observed the upregulation of several virulence factors, including genes encoding functions involved in adhesion, proteolysis, and cytotoxicity. To further explore these findings, we conducted quantitative reverse transcription-PCR (qRT-PCR) experiments to determine the influence of media composition, pH, and temperature on the transcriptional response of key factors involved in adhesion and virulence. We also demonstrated that MRSA primed in SLM adhered better to human corneocytes and demonstrated adhesin-specific phenotypes that previously required genetic manipulation. This improved adherence to corneocytes was dependent on both acidic pH and growth in SLM. These results support the potential utility of SLM as an in vitro model for assessing staphylococcal physiology and metabolism on human skin. IMPORTANCE Staphylococcus aureus is the major cause of skin diseases, and its increased prevalence in skin colonization and infections present a need to understand its physiology in this environment. The work presented here outlines S. aureus upregulation of colonization and virulence factors using a newly developed medium that strives to replicate the human skin surface environment and demonstrates roles for adhesins clumping factor A (ClfA), serine-rich repeat glycoprotein adhesin (SraP), and the fibronectin binding proteins (Fnbps) in human corneocyte adherence.
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Affiliation(s)
- Flavia G Costa
- Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Krista B Mills
- Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Heidi A Crosby
- Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Alexander R Horswill
- Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Department of Veterans Affairs, Eastern Colorado Healthcare System, Aurora, Colorado, USA
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3
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Costa FG, Mills KB, Crosby HA, Horswill AR. The Staphylococcus aureus regulatory program in a human skin-like environment. bioRxiv 2023:2023.10.24.563767. [PMID: 37961268 PMCID: PMC10634794 DOI: 10.1101/2023.10.24.563767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Staphylococcus aureus is a Gram-positive pathogen responsible for the majority of skin and soft tissue infections (SSTIs). S. aureus colonizes the anterior nares of approximately 20-30% of the population and transiently colonizes the skin, thereby increasing the risk of developing SSTIs and more serious infections. Current laboratory models that mimic the skin surface environment are expensive, require substantial infrastructure, and limit the scope of bacterial physiology studies under human skin conditions. To overcome these limitations, we developed a cost-effective, open-source, chemically defined media recipe termed skin-like media (SLM) that incorporates key aspects of the human skin surface environment and supports growth of several Staphylococcal species. We utilized SLM to investigate the transcriptional response of methicillin-resistant S. aureus (MRSA) following growth in SLM compared to a commonly used laboratory media. Through RNA-seq analysis, we observed the upregulation of several virulence factors, including genes encoding functions involved in adhesion, proteolysis, and cytotoxicity. To further explore these findings, we conducted qRT-PCR experiments to determine the influence of media composition, pH, and temperature on the transcriptional response of key factors involved in adhesion and virulence. We also demonstrated that MRSA primed in SLM adhered better to human corneocytes and demonstrated adhesin-specific phenotypes that previously required genetic manipulation. These results support the potential utility of SLM as an in vitro model for assessing Staphylococcal physiology and metabolism on human skin. Importance Staphylococcus aureus is the major cause of skin diseases, and its increased prevalence in skin colonization and infections present a need to understand its physiology in this environment. The work presented here outlines S. aureus upregulation of colonization and virulence factors using a newly developed media that strives to replicate the human skin surface environment, and demonstrates roles for adhesins ClfA, SraP, and Fnbps in human corneocyte adherence.
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Häffner N, Bär J, Dengler Haunreiter V, Mairpady Shambat S, Seidl K, Crosby HA, Horswill AR, Zinkernagel AS. Intracellular Environment and agr System Affect Colony Size Heterogeneity of Staphylococcus aureus. Front Microbiol 2020; 11:1415. [PMID: 32695082 PMCID: PMC7339952 DOI: 10.3389/fmicb.2020.01415] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Accepted: 06/02/2020] [Indexed: 12/21/2022] Open
Abstract
Staphylococcus aureus causes chronic and relapsing infections, which may be difficult to treat. So-called small colony variants (SCVs) have been associated with chronic infections and their occurrence has been shown to increase under antibiotic pressure, low pH and intracellular localization. In clinics, S. aureus isolated from invasive infections often show a dysfunction in the accessory gene regulator (agr), a major virulence regulatory system in S. aureus. To assess whether intracellular environment and agr function influence SCV formation, an infection model was established using lung epithelial cells and skin fibroblasts. This allowed analyzing intracellular survival and localization of a panel of S. aureus wild type strains and their isogenic agr knock out mutants as well as a natural dysfunctional agr strain by confocal laser scanning microscopy (CLSM). Furthermore, bacterial colonies were quantified after 1, 3, and 5 days of intracellular survival by time-lapse analysis to determine kinetics of colony appearance and SCV formation. Here, we show that S. aureus strains with an agr knock out predominantly resided in a neutral environment, whereas wild type strains and an agr complemented strain resided in an acidic environment. S. aureus agr mutants derived from an intracellular environment showed a higher percentage of SCVs as compared to their corresponding wild type strains. Neutralizing acidic phagolysosomes with chloroquine resulted in a significant reduction of SCVs in S. aureus wild type strain 6850, but not in its agr mutant indicating a pH dependent formation of SCVs in the wild type strain. The in-depth understanding of the interplay between intracellular persistence, agr function and pH should help to identify new therapeutic options facilitating the treatment of chronic S. aureus infections in the future.
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Affiliation(s)
- Nicola Häffner
- Department of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Julian Bär
- Department of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Vanina Dengler Haunreiter
- Department of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Srikanth Mairpady Shambat
- Department of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Kati Seidl
- Department of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Heidi A Crosby
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO, United States
| | - Alexander R Horswill
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO, United States.,Department of Veterans Affairs Eastern Colorado Health Care System, Denver, CO, United States
| | - Annelies S Zinkernagel
- Department of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
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5
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Crosby HA, Tiwari N, Kwiecinski JM, Xu Z, Dykstra A, Jenul C, Fuentes EJ, Horswill AR. The Staphylococcus aureus ArlRS two-component system regulates virulence factor expression through MgrA. Mol Microbiol 2020; 113:103-122. [PMID: 31618469 PMCID: PMC7175635 DOI: 10.1111/mmi.14404] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The Gram-positive bacterium, Staphylococcus aureus, is a versatile pathogen that can sense and adapt to a wide variety of environments within the human host, in part through its 16 two-component regulatory systems. The ArlRS two-component system has been shown to affect many cellular processes in S. aureus, including autolysis, biofilm formation, capsule synthesis and virulence. Yet the molecular details of this regulation remained largely unknown. We used RNA sequencing to identify the ArlRS regulon, and found 70% overlap with that of the global regulator MgrA. These genes included cell wall-anchored adhesins (ebh, sdrD), polysaccharide and capsule synthesis genes, cell wall remodeling genes (lytN, ddh), the urease operon, genes involved in metal transport (feoA, mntH, sirA), anaerobic metabolism genes (adhE, pflA, nrdDG) and a large number of virulence factors (lukSF, lukAB, nuc, gehB, norB, chs, scn and esxA). We show that ArlR directly activates expression of mgrA and identify a probable ArlR-binding site (TTTTCTCAT-N4 -TTTTAATAA). A highly similar sequence is also found in the spx P2 promoter, which was recently shown to be regulated by ArlRS. We also demonstrate that ArlS has kinase activity toward ArlR in vitro, although it has slower kinetics than other similar histidine kinases.
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Affiliation(s)
- Heidi A. Crosby
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO
| | - Nitija Tiwari
- Department of Biochemistry, University of Iowa Carver College of Medicine, Iowa City, IA
| | - Jakub M. Kwiecinski
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO
| | - Zhen Xu
- Department of Biochemistry, University of Iowa Carver College of Medicine, Iowa City, IA
| | - Allison Dykstra
- Department of Biochemistry, University of Iowa Carver College of Medicine, Iowa City, IA
| | - Christian Jenul
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO
| | - Ernesto J Fuentes
- Department of Biochemistry, University of Iowa Carver College of Medicine, Iowa City, IA
| | - Alexander R. Horswill
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO
- Department of Veterans Affairs Eastern Colorado Health Care System, Denver, CO
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6
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Miller RJ, Crosby HA, Schilcher K, Wang Y, Ortines RV, Mazhar M, Dikeman DA, Pinsker BL, Brown ID, Joyce DP, Zhang J, Archer NK, Liu H, Alphonse MP, Czupryna J, Anderson WR, Bernthal NM, Fortuno-Miranda L, Bulte JWM, Francis KP, Horswill AR, Miller LS. Development of a Staphylococcus aureus reporter strain with click beetle red luciferase for enhanced in vivo imaging of experimental bacteremia and mixed infections. Sci Rep 2019; 9:16663. [PMID: 31723175 PMCID: PMC6853927 DOI: 10.1038/s41598-019-52982-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 10/26/2019] [Indexed: 02/03/2023] Open
Abstract
In vivo bioluminescence imaging has been used to monitor Staphylococcus aureus infections in preclinical models by employing bacterial reporter strains possessing a modified lux operon from Photorhabdus luminescens. However, the relatively short emission wavelength of lux (peak 490 nm) has limited tissue penetration. To overcome this limitation, the gene for the click beetle (Pyrophorus plagiophtalamus) red luciferase (luc) (with a longer >600 emission wavelength), was introduced singly and in combination with the lux operon into a methicillin-resistant S. aureus strain. After administration of the substrate D-luciferin, the luc bioluminescent signal was substantially greater than the lux signal in vitro. The luc signal had enhanced tissue penetration and improved anatomical co-registration with infected internal organs compared with the lux signal in a mouse model of S. aureus bacteremia with a sensitivity of approximately 3 × 104 CFU from the kidneys. Finally, in an in vivo mixed bacterial wound infection mouse model, S. aureus luc signals could be spectrally unmixed from Pseudomonas aeruginosa lux signals to noninvasively monitor the bacterial burden of both strains. Therefore, the S. aureus luc reporter may provide a technological advance for monitoring invasive organ dissemination during S. aureus bacteremia and for studying bacterial dynamics during mixed infections.
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Affiliation(s)
- Robert J Miller
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Heidi A Crosby
- Department of Immunology & Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, 80045, USA
| | - Katrin Schilcher
- Department of Immunology & Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, 80045, USA
| | - Yu Wang
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Roger V Ortines
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Momina Mazhar
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Dustin A Dikeman
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Bret L Pinsker
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Isabelle D Brown
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Daniel P Joyce
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jeffrey Zhang
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Nathan K Archer
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Haiyun Liu
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Martin P Alphonse
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | | | | | - Nicholas M Bernthal
- Department of Orthopaedic Surgery, David Geffen School of Medicine at UCLA, Santa Monica, California, USA
| | - Lea Fortuno-Miranda
- Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA.,Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - Jeff W M Bulte
- Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA.,Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA.,Department of Chemical & Biomolecular Engineering, Johns Hopkins University Whiting School of Engineering, Baltimore, Maryland, 21205, USA.,Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA.,Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - Kevin P Francis
- PerkinElmer, Hopkinton, Massachusetts, USA.,Department of Orthopaedic Surgery, David Geffen School of Medicine at UCLA, Santa Monica, California, USA
| | - Alexander R Horswill
- Department of Immunology & Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, 80045, USA.,Denver VA Healthcare System, Denver, Colorado, USA
| | - Lloyd S Miller
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. .,Department of Medicine, Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21287, USA. .,Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21287, USA. .,Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, 21218, USA.
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7
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Kwiecinski JM, Crosby HA, Valotteau C, Hippensteel JA, Nayak MK, Chauhan AK, Schmidt EP, Dufrêne YF, Horswill AR. Staphylococcus aureus adhesion in endovascular infections is controlled by the ArlRS-MgrA signaling cascade. PLoS Pathog 2019; 15:e1007800. [PMID: 31116795 PMCID: PMC6548404 DOI: 10.1371/journal.ppat.1007800] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 06/04/2019] [Accepted: 04/30/2019] [Indexed: 12/31/2022] Open
Abstract
Staphylococcus aureus is a leading cause of endovascular infections. This bacterial pathogen uses a diverse array of surface adhesins to clump in blood and adhere to vessel walls, leading to endothelial damage, development of intravascular vegetations and secondary infectious foci, and overall disease progression. In this work, we describe a novel strategy used by S. aureus to control adhesion and clumping through activity of the ArlRS two-component regulatory system, and its downstream effector MgrA. Utilizing a combination of in vitro cellular assays, and single-cell atomic force microscopy, we demonstrated that inactivation of this ArlRS—MgrA cascade inhibits S. aureus adhesion to a vast array of relevant host molecules (fibrinogen, fibronectin, von Willebrand factor, collagen), its clumping with fibrinogen, and its attachment to human endothelial cells and vascular structures. This impact on S. aureus adhesion was apparent in low shear environments, and in physiological levels of shear stress, as well as in vivo in mouse models. These effects were likely mediated by the de-repression of giant surface proteins Ebh, SraP, and SasG, caused by inactivation of the ArlRS—MgrA cascade. In our in vitro assays, these giant proteins collectively shielded the function of other surface adhesins and impaired their binding to cognate ligands. Finally, we demonstrated that the ArlRS—MgrA regulatory cascade is a druggable target through the identification of a small-molecule inhibitor of ArlRS signaling. Our findings suggest a novel approach for the pharmacological treatment and prevention of S. aureus endovascular infections through targeting the ArlRS—MgrA regulatory system. Adhesion is central to the success of Staphylococcus aureus as a bacterial pathogen. We describe a novel mechanism through which S. aureus alters adhesion to ligands by regulating expression of giant inhibitory surface proteins. These giant proteins shield normal surface adhesins, preventing binding to ligands commonly found in the bloodstream and vessel walls. Using this unique regulatory scheme, S. aureus can bypass the need for individualized regulation of numerous adhesins to control overall adhesive properties. Our study establishes the importance of these giant proteins for S. aureus pathogenesis and demonstrates that a single regulatory cascade can be targeted for treating infections.
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Affiliation(s)
- Jakub M. Kwiecinski
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Heidi A. Crosby
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Claire Valotteau
- Institute of Life Sciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Joseph A. Hippensteel
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Manasa K. Nayak
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Anil K. Chauhan
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Eric P. Schmidt
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Yves F. Dufrêne
- Institute of Life Sciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium
- Walloon Excellence in Life Sciences and Biotechnology (WELBIO), Wallonia, Belgium
| | - Alexander R. Horswill
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, United States of America
- Department of Veterans Affairs Eastern Colorado Healthcare System, Denver, Colorado, United States of America
- * E-mail:
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Tian X, Hellman J, Horswill AR, Crosby HA, Francis KP, Prakash A. Corrigendum: Elevated Gut Microbiome-Derived Propionate Levels Are Associated With Reduced Sterile Lung Inflammation and Bacterial Immunity in Mice. Front Microbiol 2019; 10:518. [PMID: 30972040 PMCID: PMC6443955 DOI: 10.3389/fmicb.2019.00518] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 02/28/2019] [Indexed: 11/13/2022] Open
Abstract
[This corrects the article DOI: 10.3389/fmicb.2019.00159.].
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Affiliation(s)
- Xiaoli Tian
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA, United States
| | - Judith Hellman
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA, United States
| | - Alexander R Horswill
- Department of Immunology and Microbiology, Anschutz Medical Campus, University of Colorado, Aurora, CO, United States
| | - Heidi A Crosby
- Department of Immunology and Microbiology, Anschutz Medical Campus, University of Colorado, Aurora, CO, United States
| | - Kevin P Francis
- Preclinical Imaging, PerkinElmer, Hopkinton, MA, United States
| | - Arun Prakash
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA, United States.,San Francisco General Hospital, University of California, San Francisco, San Francisco, CA, United States
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9
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Parlet CP, Kavanaugh JS, Crosby HA, Raja HA, El-Elimat T, Todd DA, Pearce CJ, Cech NB, Oberlies NH, Horswill AR. Apicidin Attenuates MRSA Virulence through Quorum-Sensing Inhibition and Enhanced Host Defense. Cell Rep 2019; 27:187-198.e6. [PMID: 30943400 PMCID: PMC7224364 DOI: 10.1016/j.celrep.2019.03.018] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 01/27/2019] [Accepted: 03/05/2019] [Indexed: 11/15/2022] Open
Abstract
Recurrent epidemics of drug-resistant Staphylococcus aureus illustrate the rapid lapse of antibiotic efficacy following clinical implementation. Over the last decade, community-associated methicillin-resistant S. aureus (MRSA) has emerged as a dominant cause of infections, and this problem is amplified by the hyper-virulent nature of these isolates. Herein, we report the discovery of a fungal metabolite, apicidin, as an innovative means to counter both resistance and virulence. Owing to its breadth and specificity as a quorum-sensing inhibitor, apicidin antagonizes all MRSA agr systems in a non-biocidal manner. In skin challenge experiments, the apicidin-mediated abatement of MRSA pathogenesis corresponds with quorum-sensing inhibition at in vivo sites of infection. Additionally, we show that apicidin attenuates MRSA-induced disease by potentiating innate effector responses, particularly through enhanced neutrophil accumulation and function at cutaneous challenge sites. Together, these results indicate that apicidin treatment represents a strategy to limit MRSA virulence and promote host defense.
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Affiliation(s)
- Corey P Parlet
- Roy J. and Lucille A. Carver College of Medicine, Department of Microbiology, University of Iowa, Iowa City, IA, USA
| | - Jeffrey S Kavanaugh
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Heidi A Crosby
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Huzefa A Raja
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, USA
| | - Tamam El-Elimat
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, USA
| | - Daniel A Todd
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, USA
| | | | - Nadja B Cech
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, USA
| | - Nicholas H Oberlies
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, USA
| | - Alexander R Horswill
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO, USA; Department of Veterans Affairs, Eastern Colorado Healthcare System, Aurora, CO, USA.
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Tian X, Hellman J, Horswill AR, Crosby HA, Francis KP, Prakash A. Elevated Gut Microbiome-Derived Propionate Levels Are Associated With Reduced Sterile Lung Inflammation and Bacterial Immunity in Mice. Front Microbiol 2019; 10:159. [PMID: 30891007 PMCID: PMC6413706 DOI: 10.3389/fmicb.2019.00159] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 01/22/2019] [Indexed: 12/14/2022] Open
Abstract
Short-chain fatty acids (SCFA) are important dietary and microbiome metabolites that can have roles in gut immunity as well as further afield. We previously observed that gut microbiome alteration via antibiotics led to attenuated lung inflammatory responses. The rationale for this study was to identify gut microbiome factors that regulate lung immune homeostasis. We first investigated key factors within mouse colonic lumen filtrates (CLF) which could elicit direct inflammatory effects in vitro. We identified lipopolysaccharide (LPS) and SCFAs as key CLF ingredients whose levels and inflammatory capacity changed after antibiotic exposure in mice. Specifically, the SCFA propionate appeared to be a key regulator of LPS responses in vitro. Elevated propionate: acetate ratios, as seen in CLF after antibiotic exposure, strongly blunted inflammatory responses in vitro. In vivo, exposure of lungs to high dose propionate, to mimic how prior antibiotic exposure changed SCFA levels, resulted in diminished immune containment of Staphylococcus aureus pneumonia. Finally, we discovered an enrichment of propionate-producing gut bacteria in mice with reduced lung inflammation following lung ischemia reperfusion injury in vivo. Overall, our data show that propionate levels can distinctly modulate lung immune responses in vitro and in vivo and that gut microbiome increased production of propionate is associated with reduced lung inflammation.
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Affiliation(s)
- Xiaoli Tian
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA, United States
| | - Judith Hellman
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA, United States
| | - Alexander R. Horswill
- Department of Immunology and Microbiology, Anschutz Medical Campus, University of Colorado, Aurora, CO, United States
| | - Heidi A. Crosby
- Department of Immunology and Microbiology, Anschutz Medical Campus, University of Colorado, Aurora, CO, United States
| | | | - Arun Prakash
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA, United States.,San Francisco General Hospital, University of California, San Francisco, San Francisco, CA, United States
Approved by: Frontiers in Microbiology Editorial Office, Frontiers Media SA, Switzerland
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Trivedi U, Madsen JS, Everett J, Fell C, Russel J, Haaber J, Crosby HA, Horswill AR, Burmølle M, Rumbaugh KP, Sørensen SJ. Staphylococcus aureus coagulases are exploitable yet stable public goods in clinically relevant conditions. Proc Natl Acad Sci U S A 2018; 115:E11771-E11779. [PMID: 30463950 PMCID: PMC6294911 DOI: 10.1073/pnas.1804850115] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Coagulation is an innate defense mechanism intended to limit blood loss and trap invading pathogens during infection. However, Staphylococcus aureus has the ability to hijack the coagulation cascade and generate clots via secretion of coagulases. Although many S. aureus have this characteristic, some do not. The population dynamics regarding this defining trait have yet to be explored. We report here that coagulases are public goods that confer protection against antimicrobials and immune factors within a local population or community, thus promoting growth and virulence. By utilizing variants of a methicillin-resistant S. aureus we infer that the secretion of coagulases is a cooperative trait, which is subject to exploitation by invading mutants that do not produce the public goods themselves. However, overexploitation, "tragedy of the commons," does not occur at clinically relevant conditions. Our micrographs indicate this is due to spatial segregation and population viscosity. These findings emphasize the critical role of coagulases in a social evolution context and provide a possible explanation as to why the secretion of these public goods is maintained in mixed S. aureus communities.
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Affiliation(s)
- Urvish Trivedi
- Section of Microbiology, Department of Biology, Faculty of Science, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Jonas S Madsen
- Section of Microbiology, Department of Biology, Faculty of Science, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Jake Everett
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, TX 79430
| | - Cody Fell
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, TX 79430
| | - Jakob Russel
- Section of Microbiology, Department of Biology, Faculty of Science, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Jakob Haaber
- Department of Veterinary and Animal Sciences, Faculty of Health & Medical Sciences, University of Copenhagen, 1870 Copenhagen, Denmark
| | - Heidi A Crosby
- Department of Immunology and Microbiology, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045
| | - Alexander R Horswill
- Department of Immunology and Microbiology, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045
| | - Mette Burmølle
- Section of Microbiology, Department of Biology, Faculty of Science, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Kendra P Rumbaugh
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, TX 79430
| | - Søren J Sørensen
- Section of Microbiology, Department of Biology, Faculty of Science, University of Copenhagen, 2100 Copenhagen, Denmark;
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Quave CL, Lyles JT, Kavanaugh JS, Nelson K, Parlet CP, Crosby HA, Heilmann KP, Horswill AR. Correction: Castanea sativa (European Chestnut) Leaf Extracts Rich in Ursene and Oleanene Derivatives Block Staphylococcus aureus Virulence and Pathogenesis without Detectable Resistance. PLoS One 2016; 11:e0163655. [PMID: 27657727 PMCID: PMC5033592 DOI: 10.1371/journal.pone.0163655] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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13
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Crosby HA, Kwiecinski J, Horswill AR. Staphylococcus aureus Aggregation and Coagulation Mechanisms, and Their Function in Host-Pathogen Interactions. Adv Appl Microbiol 2016; 96:1-41. [PMID: 27565579 DOI: 10.1016/bs.aambs.2016.07.018] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The human commensal bacterium Staphylococcus aureus can cause a wide range of infections ranging from skin and soft tissue infections to invasive diseases like septicemia, endocarditis, and pneumonia. Muticellular organization almost certainly contributes to S. aureus pathogenesis mechanisms. While there has been considerable focus on biofilm formation and its role in colonizing prosthetic joints and indwelling devices, less attention has been paid to nonsurface-attached group behavior like aggregation and clumping. S. aureus is unique in its ability to coagulate blood, and it also produces multiple fibrinogen-binding proteins that facilitate clumping. Formation of clumps, which are large, tightly packed groups of cells held together by fibrin(ogen), has been demonstrated to be important for S. aureus virulence and immune evasion. Clumps of cells are able to avoid detection by the host's immune system due to a fibrin(ogen) coat that acts as a shield, and the size of the clumps facilitates evasion of phagocytosis. In addition, clumping could be an important early step in establishing infections that involve tight clusters of cells embedded in host matrix proteins, such as soft tissue abscesses and endocarditis. In this review, we discuss clumping mechanisms and regulation, as well as what is known about how clumping contributes to immune evasion.
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Affiliation(s)
- H A Crosby
- University of Iowa, Iowa City, IA, United States
| | - J Kwiecinski
- University of Iowa, Iowa City, IA, United States
| | - A R Horswill
- University of Iowa, Iowa City, IA, United States
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14
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Parlet CP, Kavanaugh JS, Crosby HA, Cech NB, Oberlies NH, Horswill AR. Apicidin mediated attenuation of MRSA virulence corresponds with quorum sensing inhibition and enhanced immune effector responses. The Journal of Immunology 2016. [DOI: 10.4049/jimmunol.196.supp.206.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
As the leading cause of infectious mortality in the United States, S. aureus-induced disease represents a major healthcare problem. The alarming rise of infections caused by virulent, antibiotic resistant strains, such as emerging methicillin-resistant S. aureus (MRSA) isolates, highlight the need for new interventions that inhibit MRSA pathogenicity and potentiate host defense responses. The expression of MRSA virulence factors is a function of agr-driven quorum sensing, making this system a promising target for anti-MRSA therapies. Through agr-reporter-based screens, a class of compounds, called apicidins, were found to inhibit quorum-sensing activity across MRSA isolates. To test the efficacy of apicidin in vivo, mice were challenged intradermally with 2×107 MRSA (+/−) 5 mg apicidin. The abatement MRSA virulence in the apicidin-treated group was demonstrated by reduced: weight loss, dermonecrosis and cutaneous bacterial burden. By challenging mice with an agr-reporter strain, we also found that the apicidin-mediated attenuation of MRSA pathogenesis corresponded with reduced quorum sensing activity in vivo. To evaluate apicidin’s impact upon anti-MRSA effector responses, we assessed polymorphonuclear neutrophil (PMN) accumulation and function at cutaneous sites of infection. Flow cytometric analysis revealed that apicidin increased the density of PMNs within infected wounds 24 hours post infection. In addition, we found that the number of PMNs that phagocytosed MRSA organisms in vivo was increased in lesional skin preparations from apicidin treated mice. Together, these results indicate that apicidin-mediated quorum quenching represents a novel strategy to limit MRSA virulence and promote host defense.
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Quave CL, Lyles JT, Kavanaugh JS, Nelson K, Parlet CP, Crosby HA, Heilmann KP, Horswill AR. Castanea sativa (European Chestnut) Leaf Extracts Rich in Ursene and Oleanene Derivatives Block Staphylococcus aureus Virulence and Pathogenesis without Detectable Resistance. PLoS One 2015; 10:e0136486. [PMID: 26295163 PMCID: PMC4546677 DOI: 10.1371/journal.pone.0136486] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 08/04/2015] [Indexed: 01/08/2023] Open
Abstract
The Mediterranean is home to a rich history of medical traditions that have developed under the influence of diverse cultures over millennia. Today, many such traditions are still alive in the folk medical practices of local people. Investigation of botanical folk medicines used in the treatment of skin and soft tissue infections led us to study Castanea sativa (European Chestnut) for its potential antibacterial activity. Here, we report the quorum sensing inhibitory activity of refined and chemically characterized European Chestnut leaf extracts, rich in oleanene and ursene derivatives (pentacyclic triterpenes), against all Staphylococcus aureus accessory gene regulator (agr) alleles. We present layers of evidence of agr blocking activity (IC50 1.56–25 μg mL-1), as measured in toxin outputs, reporter assays hemolytic activity, cytotoxicity studies, and an in vivo abscess model. We demonstrate the extract’s lack of cytotoxicity to human keratinocytes and murine skin, as well as lack of growth inhibitory activity against S. aureus and a panel of skin commensals. Lastly, we demonstrate that serial passaging of the extract does not result in acquisition of resistance to the quorum quenching composition. In conclusion, through disruption of quorum sensing in the absence of growth inhibition, this study provides insight into the role that non-biocide inhibitors of virulence may play in future antibiotic therapies.
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Affiliation(s)
- Cassandra L. Quave
- Center for the Study of Human Health, Emory University, Atlanta, Georgia, United States of America
- Department of Dermatology, Emory University School of Medicine, Atlanta, Georgia, United States of America
- * E-mail:
| | - James T. Lyles
- Center for the Study of Human Health, Emory University, Atlanta, Georgia, United States of America
| | - Jeffery S. Kavanaugh
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Kate Nelson
- Department of Dermatology, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Corey P. Parlet
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Heidi A. Crosby
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Kristopher P. Heilmann
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Alexander R. Horswill
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
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16
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Mootz JM, Benson MA, Heim CE, Crosby HA, Kavanaugh JS, Dunman PM, Kielian T, Torres VJ, Horswill AR. Rot is a key regulator of Staphylococcus aureus biofilm formation. Mol Microbiol 2015; 96:388-404. [PMID: 25612137 DOI: 10.1111/mmi.12943] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2015] [Indexed: 01/28/2023]
Abstract
Staphylococcus aureus is a significant cause of chronic biofilm infections on medical implants. We investigated the biofilm regulatory cascade and discovered that the repressor of toxins (Rot) is part of this pathway. A USA300 community-associated methicillin-resistant S. aureus strain deficient in Rot was unable to form a biofilm using multiple different assays, and we found rot mutants in other strain lineages were also biofilm deficient. By performing a global analysis of transcripts and protein production controlled by Rot, we observed that all the secreted protease genes were up-regulated in a rot mutant, and we hypothesized that this regulation could be responsible for the biofilm phenotype. To investigate this question, we determined that Rot bound to the protease promoters, and we observed that activity levels of these enzymes, in particular the cysteine proteases, were increased in a rot mutant. By inactivating these proteases, biofilm capacity was restored to the mutant, demonstrating they are responsible for the biofilm negative phenotype. Finally, we tested the rot mutant in a mouse catheter model of biofilm infection and observed a significant reduction in biofilm burden. Thus S. aureus uses the transcription factor Rot to repress secreted protease levels in order to build a biofilm.
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Affiliation(s)
- Joe M Mootz
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
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Kiedrowski MR, Crosby HA, Hernandez FJ, Malone CL, McNamara JO, Horswill AR. Staphylococcus aureus Nuc2 is a functional, surface-attached extracellular nuclease. PLoS One 2014; 9:e95574. [PMID: 24752186 PMCID: PMC3994088 DOI: 10.1371/journal.pone.0095574] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 03/28/2014] [Indexed: 12/30/2022] Open
Abstract
Staphylococcus aureus is a prominent bacterial pathogen that causes a diverse range of acute and chronic infections. Recently, it has been demonstrated that the secreted nuclease (Nuc) enzyme is a virulence factor in multiple models of infection, and in vivo expression of nuc has facilitated the development of an infection imaging approach based on Nuc-activatable probes. Interestingly, S. aureus strains encode a second nuclease (Nuc2) that has received limited attention. With the growing interest in bacterial nucleases, we sought to characterize Nuc2 in more detail through localization, expression, and biochemical studies. Fluorescence microscopy and alkaline phosphatase localization approaches using Nuc2-GFP and Nuc2-PhoA fusions, respectively, demonstrated that Nuc2 is membrane bound with the C-terminus facing the extracellular environment, indicating it is a signal-anchored Type II membrane protein. Nuc2 enzyme activity was detectable on the S. aureus cell surface using a fluorescence resonance energy transfer (FRET) assay, and in time courses, both nuc2 transcription and enzyme activity peaked in early logarithmic growth and declined in stationary phase. Using a mouse model of S. aureus pyomyositis, Nuc2 activity was detected with activatable probes in vivo in nuc mutant strains, demonstrating that Nuc2 is produced during infections. To assess Nuc2 biochemical properties, the protein was purified and found to cleave both single- and double-stranded DNA, and it exhibited thermostability and calcium dependence, paralleling the properties of Nuc. Purified Nuc2 prevented biofilm formation in vitro and modestly decreased biomass in dispersal experiments. Altogether, our findings confirm that S. aureus encodes a second, surface-attached and functional DNase that is expressed during infections and displays similar biochemical properties to the secreted Nuc enzyme.
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Affiliation(s)
- Megan R. Kiedrowski
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Heidi A. Crosby
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Frank J. Hernandez
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Cheryl L. Malone
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - James O. McNamara
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Alexander R. Horswill
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
- * E-mail:
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18
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Walker JN, Crosby HA, Spaulding AR, Salgado-Pabón W, Malone CL, Rosenthal CB, Schlievert PM, Boyd JM, Horswill AR. The Staphylococcus aureus ArlRS two-component system is a novel regulator of agglutination and pathogenesis. PLoS Pathog 2013; 9:e1003819. [PMID: 24367264 PMCID: PMC3868527 DOI: 10.1371/journal.ppat.1003819] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 10/21/2013] [Indexed: 01/31/2023] Open
Abstract
Staphylococcus aureus is a prominent bacterial pathogen that is known to agglutinate in the presence of human plasma to form stable clumps. There is increasing evidence that agglutination aids S. aureus pathogenesis, but the mechanisms of this process remain to be fully elucidated. To better define this process, we developed both tube based and flow cytometry methods to monitor clumping in the presence of extracellular matrix proteins. We discovered that the ArlRS two-component system regulates the agglutination mechanism during exposure to human plasma or fibrinogen. Using divergent S. aureus strains, we demonstrated that arlRS mutants are unable to agglutinate, and this phenotype can be complemented. We found that the ebh gene, encoding the Giant Staphylococcal Surface Protein (GSSP), was up-regulated in an arlRS mutant. By introducing an ebh complete deletion into an arlRS mutant, agglutination was restored. To assess whether GSSP is the primary effector, a constitutive promoter was inserted upstream of the ebh gene on the chromosome in a wildtype strain, which prevented clump formation and demonstrated that GSSP has a negative impact on the agglutination mechanism. Due to the parallels of agglutination with infective endocarditis development, we assessed the phenotype of an arlRS mutant in a rabbit combined model of sepsis and endocarditis. In this model the arlRS mutant displayed a large defect in vegetation formation and pathogenesis, and this phenotype was partially restored by removing GSSP. Altogether, we have discovered that the ArlRS system controls a novel mechanism through which S. aureus regulates agglutination and pathogenesis. Staphylococcus aureus is a bacterial pathogen that is responsible for causing significant disease in humans. The development of antibiotic resistant strains has made these infections more difficult to treat, and an improved understanding of how this pathogen causes infections will facilitate the development of new tools for treatment. It has long been recognized that S. aureus can bind human matrix proteins to form stable clumps in a process called agglutination, but the importance of agglutination during infection is only just becoming understood. In this work, we developed several techniques to investigate the S. aureus agglutination mechanism. We discovered that the ArlRS two-component regulatory system controls agglutination by regulating the expression of the ebh gene, which encodes the Giant Staphylococcal Surface Protein (GSSP). When ArlRS is non-functional, S. aureus agglutination is prevented through the action of GSSP. These phenotypes were confirmed in a rabbit model of sepsis and infective endocarditis, demonstrating that ArlRS is an important regulator of virulence. Taken together, the identification of ArlRS as a regulator of S. aureus agglutination and pathogenesis may lead to innovative directions for therapeutic development.
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Affiliation(s)
- Jennifer N Walker
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Heidi A Crosby
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Adam R Spaulding
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Wilmara Salgado-Pabón
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Cheryl L Malone
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Carolyn B Rosenthal
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Patrick M Schlievert
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Jeffrey M Boyd
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, New Jersey, United States of America
| | - Alexander R Horswill
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
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Crosby HA, Rank KC, Rayment I, Escalante-Semerena JC. Structural insights into the substrate specificity of the Rhodopseudomonas palustris protein acetyltransferase RpPat: identification of a loop critical for recognition by RpPat. J Biol Chem 2012; 287:41392-404. [PMID: 23076154 DOI: 10.1074/jbc.m112.417360] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Lysine acetylation is a post-translational modification that is important for the regulation of metabolism in both prokaryotes and eukaryotes. In bacteria, the best studied protein acetyltransferase is Pat. In the purple photosynthetic bacterium Rhodopseudomonas palustris, at least 10 AMP-forming acyl-CoA synthetase enzymes are acetylated by the Pat homologue RpPat. All bona fide RpPat substrates contain the conserved motif PX(4)GK. Here, we show that the presence of such a motif is necessary but not sufficient for recognition by RpPat. RpPat failed to acetylate the methylmalonyl-CoA synthetase of this bacterium (hereafter RpMatB) in vivo and in vitro, despite the homology of RpMatB to known RpPat substrates. We used RpMatB to identify structural determinants that are recognized by RpPat. To do this, we constructed a series of RpMatB chimeras that became substrates of RpPat. In such chimeras, a short region (11-25 residues) of RpMatB located >20 residues N-terminal to the acetylation site was replaced with the corresponding sequences from other AMP-forming acyl-CoA synthetases that were known RpPat substrates. Strikingly, the enzymatic activity of RpMatB chimeras was regulated by acetylation both in vitro and in vivo. Crystal structures of two of these chimeras showed that the major difference between them and wild-type RpMatB was within a loop region ∼23 Å from the acetylation site. On the basis of these results, we suggest that RpPat likely interacts with a relatively large surface of its substrates, in addition to the PX(4)GK motif, and that RpPat probably has relatively narrow substrate specificity.
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Affiliation(s)
- Heidi A Crosby
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin 53706, USA
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20
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Crosby HA, Pelletier DA, Hurst GB, Escalante-Semerena JC. System-wide studies of N-lysine acetylation in Rhodopseudomonas palustris reveal substrate specificity of protein acetyltransferases. J Biol Chem 2012; 287:15590-601. [PMID: 22416131 DOI: 10.1074/jbc.m112.352104] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
N-lysine acetylation is a posttranslational modification that has been well studied in eukaryotes and is likely widespread in prokaryotes as well. The central metabolic enzyme acetyl-CoA synthetase is regulated in both bacteria and eukaryotes by acetylation of a conserved lysine residue in the active site. In the purple photosynthetic α-proteobacterium Rhodopseudomonas palustris, two protein acetyltransferases (RpPat and the newly identified RpKatA) and two deacetylases (RpLdaA and RpSrtN) regulate the activities of AMP-forming acyl-CoA synthetases. In this work, we used LC/MS/MS to identify other proteins regulated by the N-lysine acetylation/deacetylation system of this bacterium. Of the 24 putative acetylated proteins identified, 14 were identified more often in a strain lacking both deacetylases. Nine of these proteins were members of the AMP-forming acyl-CoA synthetase family. RpPat acetylated all nine of the acyl-CoA synthetases identified by this work, and RpLdaA deacetylated eight of them. In all cases, acetylation occurred at the conserved lysine residue in the active site, and acetylation decreased activity of the enzymes by >70%. Our results show that many different AMP-forming acyl-CoA synthetases are regulated by N-lysine acetylation. Five non-acyl-CoA synthetases were identified as possibly acetylated, including glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and Rpa1177, a putative 4-oxalocrotonate tautomerase. Neither RpPat nor RpKatA acetylated either of these proteins in vitro. It has been reported that Salmonella enterica Pat (SePat) can acetylate a number of metabolic enzymes, including GAPDH, but we were unable to confirm this claim, suggesting that the substrate range of SePat is not as broad as suggested previously.
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Affiliation(s)
- Heidi A Crosby
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin 53706, USA
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21
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Chan CH, Garrity J, Crosby HA, Escalante-Semerena JC. In Salmonella enterica, the sirtuin-dependent protein acylation/deacylation system (SDPADS) maintains energy homeostasis during growth on low concentrations of acetate. Mol Microbiol 2011; 80:168-83. [PMID: 21306440 DOI: 10.1111/j.1365-2958.2011.07566.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Acetyl-coenzyme A synthetase (Acs) activates acetate into acetyl-coenzyme A (Ac-CoA) in most cells. In Salmonella enterica, acs expression and Acs activity are controlled. It is unclear why the sirtuin-dependent protein acylation/deacylation system (SDPADS) controls the activity of Acs. Here we show that, during growth on 10 mM acetate, acs(+) induction in a S. enterica strain that cannot acetylate (i.e. inactivate) Acs leads to growth arrest, a condition that correlates with a drop in energy charge (0.17) in the acetylation-deficient strain, relative to the energy charge in the acetylation-proficient strain (0.71). Growth arrest was caused by elevated Acs activity, a conclusion supported by the isolation of a single-amino-acid variant (Acs(G266S)), whose overproduction did not arrest growth. Acs-dependent depletion of ATP, coupled with the rise in AMP levels, prevented the synthesis of ADP needed to replenish the pool of ATP. Consistent with this idea, overproduction of ADP-forming Ac-CoA-synthesizing systems did not affect the growth behaviour of acetylation-deficient or acetylation-proficient strains. The Acs(G266S) variant was >2 orders of magnitude less efficient than the Acs(WT) enzyme, but still supported growth on 10 mM acetate. This work provides the first evidence that SDPADS function helps cells maintain energy homeostasis during growth on acetate.
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Affiliation(s)
- Chi Ho Chan
- Department of Bacteriology, University of Wisconsin, 6478 Microbial Sciences Building, 1550 Linden Dr, Madison, WI 53706-1521, USA
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Crosby HA, Heiniger EK, Harwood CS, Escalante-Semerena JC. Reversible N epsilon-lysine acetylation regulates the activity of acyl-CoA synthetases involved in anaerobic benzoate catabolism in Rhodopseudomonas palustris. Mol Microbiol 2010; 76:874-88. [PMID: 20345662 DOI: 10.1111/j.1365-2958.2010.07127.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Rhodopseudomonas palustris grows photoheterotrophically on aromatic compounds available in aquatic environments rich in plant-derived lignin. Benzoate degradation is regulated at the transcriptional level in R. palustris in response to anoxia and the presence of benzoate and/or benzoyl-CoA (Bz-CoA). Here, we report evidence that anaerobic benzoate catabolism in this bacterium is also regulated at the post-translational level. In this pathway, benzoate is activated to Bz-CoA by the AMP-forming Bz-CoA synthetase (BadA) enzyme. Mass spectrometry and mutational analysis data indicate that residue Lys512 is critical to BadA activity. Acetylation of Lys512 inactivated BadA; deacetylation reactivated BadA. Likewise, 4-hydroxybenzoyl-CoA (HbaA) and cyclohexanecarboxyl-CoA (AliA) synthetases were also reversibly acetylated. We identified one acetyltransferase that modified BadA, Hba and AliA in vitro. The acetyltransferase enzyme is homologous to the protein acetyltransferase (Pat) enzyme of Salmonella enterica sv Typhimurium LT2, thus we refer to it as RpPat. RpPat also modified acetyl-CoA (Ac-CoA) synthetase (Acs) from R. palustris. In vivo data indicate that at least two deacetylases reactivate BadA(Ac). One is SrtN (encoded by srtN, formerly rpa2524), a sirtuin-type NAD(+)-dependent deacetylase (O-acetyl-ADPribose-forming); the other deacetylase is LdaA (encoded by ldaA, for lysine deacetylase A; formerly rpa0954), an acetate-forming protein deacetylase. LdaA reactivated Hba(Ac) and AliA(Ac)in vitro.
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Affiliation(s)
- Heidi A Crosby
- Department of Bacteriology, University of Wisconsin, Madison, WI 53706, USA
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23
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Kavanagh DPJ, Durant LE, Crosby HA, Lalor PF, Frampton J, Adams DH, Kalia N. Haematopoietic stem cell recruitment to injured murine liver sinusoids depends on (alpha)4(beta)1 integrin/VCAM-1 interactions. Gut 2010; 59:79-87. [PMID: 19828466 DOI: 10.1136/gut.2008.168054] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
OBJECTIVE Evidence suggests haematopoietic stem cells (HSCs) can migrate to injured liver and influence tissue repair. However, mechanisms governing HSC recruitment to injured hepatic microcirculation are poorly understood. These were investigated in vivo following hepatic ischaemia-reperfusion (IR) injury and in vitro using flow-based adhesion assays. DESIGN Partial IR was induced in anaesthetised WT or PECAM-1(-/-) mice for 90 min. Recruitment of systemically administered HSCs was monitored and effects of function blocking antibodies against alpha(4)beta(1) integrin, CD18, CD44, PECAM-1 or VCAM-1 investigated. The kinetics and molecular events governing adhesion to murine cardiac endothelial cells in vitro were also determined. Effects of conditioned media from IR injured liver on HSC adhesion molecule expression was determined by FACS. RESULTS Administered HSCs homed predominantly to lungs rather than liver, highlighting a potential therapeutic hurdle. Hepatic HSC recruitment following IR injury was inhibited by anti-alpha(4)beta(1) and anti-VCAM-1 antibodies. A role for alpha(4)beta(1) was also confirmed using flow-based adhesion assays. Incubating HSCs with conditioned media from IR injured liver increased alpha(4)beta(1) expression. CD18, CD44 and PECAM-1 were not involved in recruitment. CONCLUSIONS This novel study demonstrates that the alpha(4)beta(1)/VCAM-1 pathway mediates HSC recruitment to injured liver. Manipulating this pathway may enhance delivery of HSCs to the liver.
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Affiliation(s)
- D P J Kavanagh
- Centre for Cardiovascular Sciences, Institute of Biomedical Research, The Medical School, University of Birmingham, Edgbaston, Birmingham, UK
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24
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Felnagle EA, Rondon MR, Berti AD, Crosby HA, Thomas MG. Identification of the biosynthetic gene cluster and an additional gene for resistance to the antituberculosis drug capreomycin. Appl Environ Microbiol 2007; 73:4162-70. [PMID: 17496129 PMCID: PMC1932801 DOI: 10.1128/aem.00485-07] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Capreomycin (CMN) belongs to the tuberactinomycin family of nonribosomal peptide antibiotics that are essential components of the drug arsenal for the treatment of multidrug-resistant tuberculosis. Members of this antibiotic family target the ribosomes of sensitive bacteria and disrupt the function of both subunits of the ribosome. Resistance to these antibiotics in Mycobacterium species arises due to mutations in the genes coding for the 16S or 23S rRNA but can also arise due to mutations in a gene coding for an rRNA-modifying enzyme, TlyA. While Mycobacterium species develop resistance due to alterations in the drug target, it has been proposed that the CMN-producing bacterium, Saccharothrix mutabilis subsp. capreolus, uses CMN modification as a mechanism for resistance rather than ribosome modification. To better understand CMN biosynthesis and resistance in S. mutabilis subsp. capreolus, we focused on the identification of the CMN biosynthetic gene cluster in this bacterium. Here, we describe the cloning and sequence analysis of the CMN biosynthetic gene cluster from S. mutabilis subsp. capreolus ATCC 23892. We provide evidence for the heterologous production of CMN in the genetically tractable bacterium Streptomyces lividans 1326. Finally, we present data supporting the existence of an additional CMN resistance gene. Initial work suggests that this resistance gene codes for an rRNA-modifying enzyme that results in the formation of CMN-resistant ribosomes that are also resistant to the aminoglycoside antibiotic kanamycin. Thus, S. mutabilis subsp. capreolus may also use ribosome modification as a mechanism for CMN resistance.
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Affiliation(s)
- Elizabeth A Felnagle
- Department of Bacteriology, University of Wisconsin-Madison, 150 Biochemistry, 420 Henry Mall, Madison, WI 53706, USA
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25
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Crosby HA, Johnson CM, Roden EE, Beard BL. Coupled Fe(II)-Fe(III) electron and atom exchange as a mechanism for Fe isotope fractionation during dissimilatory iron oxide reduction. Environ Sci Technol 2005; 39:6698-704. [PMID: 16190229 DOI: 10.1021/es0505346] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Microbial dissimilatory iron reduction (DIR) is an important pathway for carbon oxidation in anoxic sediments, and iron isotopes may distinguish between iron produced by DIR and other sources of aqueous Fe(II). Previous studies have shown that aqueous Fe(II) produced during the earliest stages of DIR has delta56Fe values that are 0.5-2.0%o lowerthan the initial Fe(III) substrate. The new experiments reported here suggest that this fractionation is controlled by coupled electron and Fe atom exchange between Fe(II) and Fe(III) at iron oxide surfaces. In hematite and goethite reduction experiments with Geobacter sulfurreducens, the 56Fe/54Fe isotopic fractionation between aqueous Fe(II) and the outermost layers of Fe(III) on the oxide surface is approximately -3%o and can be explained by equilibrium Fe isotope partitioning between reactive Fe(II) and Fe(III) pools that coexist during DIR. The results indicate that sorption of Fe(II) to Fe(III) substrates cannot account for production of low-delta56Fe values for aqueous Fe(II) during DIR.
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Affiliation(s)
- Heidi A Crosby
- Department of Geology and Geophysics, University of Wisconsin-Madison, 1215 West Dayton Street, Madison, Wisconsin 53706, USA.
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26
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Nijjar SS, Crosby HA, Wallace L, Hubscher SG, Strain AJ. Notch receptor expression in adult human liver: a possible role in bile duct formation and hepatic neovascularization. Hepatology 2001; 34:1184-92. [PMID: 11732008 DOI: 10.1053/jhep.2001.29399] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Notch signaling is an evolutionarily conserved mechanism, used to regulate cell fate decisions. Four Notch receptors have been identified in man (Notch-1 to -4). In this study, semiquantitative reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry were used to examine the expression pattern of Notch receptor genes in whole adult human liver and isolated liver cell preparations. All 4 receptors were expressed in the adult liver, with no significant differences in the levels of Notch-1, -2, and -4 messenger RNA (mRNA) between normal and diseased liver. However, Notch-3 expression appeared to be increased in diseased tissue. The distribution of Notch-1 and -4 in normal tissue was similar, with Notch-1 also detectable at low levels in the sinusoidal endothelium. Notch-2 expression was more widely distributed, and detectable in hepatocytes, medium-sized bile ducts, and the sinusoidal endothelium. Notch-3 expression was seen on hepatocytes, with weaker expression detectable in portal veins, hepatic arteries, and the sinusoids. In normal liver tissue Notch-1, -2, and -3 were found to be coexpressed on bile duct epithelium; however, with the exception of Notch-3 in primary sclerosing cholangitis (PSC) livers, expression was absent on proliferating ductules in all disease states examined. Interestingly, the expression of Notch-2 and -3 was associated with numerous small vessels within the portal tract septa of diseased tissue. The absence of Notch receptor expression on proliferating bile ductules and its presence on neovessels suggests that Notch signaling may be important for normal bile duct formation and the aberrant neovascularization seen in diseased liver tissue.
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Affiliation(s)
- S S Nijjar
- School of Biosciences, University of Birmingham, Birmingham, UK
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Afford SC, Ahmed-Choudhury J, Randhawa S, Russell C, Youster J, Crosby HA, Eliopoulos A, Hubscher SG, Young LS, Adams DH. CD40 activation-induced, Fas-dependent apoptosis and NF-kappaB/AP-1 signaling in human intrahepatic biliary epithelial cells. FASEB J 2001; 15:2345-54. [PMID: 11689460 DOI: 10.1096/fj.01-0088com] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Fas-mediated mechanisms of apoptosis are thought to be involved in the bile duct loss that characterizes diseases such as primary biliary cirrhosis (PBC). We have previously shown that activation of CD40 on hepatocytes can amplify Fas-mediated apoptosis; in the present study, we investigated interactions between CD40 and Fas in biliary epithelial cells (BEC). We report that the bile ducts in PBC liver tissue frequently express increased levels of Fas, Fas ligand (FasL), and CD40 associated with apoptotic BEC. The portal mononuclear infiltrate contains CD40L+ve T cells and macrophages, thereby demonstrating a potential mechanism for CD40 engagement in vivo. Primary cultures of human BEC also expressed Fas, FasL, and CD40 but not CD40L protein or mRNA. Activation of CD40 on BEC using recombinant CD40L increased transcriptional expression of FasL and induced apoptosis, which was inhibited by neutralizing antibodies to either Fas or FasL. Thus, CD40-induced apoptosis of BEC is mediated through Fas/FasL. We then investigated the intracellular signals and transcription factors activated in BEC and found that NF-kappaB and AP-1 were both activated after CD40 ligation. Increased functional NF-kappaB was seen early after CD40 ligation, but returned to baseline levels after 4 h. In contrast, the rapid up-regulation of AP-1 was sustained over 24 h. This study provides further functional evidence of the ability of CD40 to induce Fas/FasL-dependent apoptosis of liver epithelial cells supporting the importance of cross-talk between tumor necrosis factor (TNF) receptor family members as an amplification step in apoptosis induction. Sustained activation of AP-1 in the absence of NF-kappaB signaling may be a critical factor in determining the outcome of CD40 engagement.
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Affiliation(s)
- S C Afford
- The Liver Research Laboratories, MRC Centre for Immune Regulation, Queen Elizabeth Hospital, Birmingham B15 2TH, UK.
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Abstract
BACKGROUND & AIMS Recent reports suggest that after bone marrow transplantation into rodents and humans, hematopoietic stem cells migrate into the liver and give rise to oval cells, hepatocytes, and biliary epithelial cells. We investigated this hypothesis further in the human liver using the hematopoietic markers c-kit and CD34. METHODS Immunofluorescence confocal microscopy was performed using cytokeratin 19 (CK-19; biliary cell marker) with either c-kit or CD34. Immunomagnetic separation was then used to select c-kit- or CD34-positive cells. After attachment, cells were cultured for up to 7 days, and their growth and phenotypic characteristics were examined. RESULTS In cirrhotic tissue, c-kit- or CD34-positive cells were located in the portal tracts surrounding bile ducts. Occasionally c-kit- (but not CD34-) positive cells that coexpressed CK-19 were observed integrated into bile ducts. In vitro, immunoisolated c-kit or CD34 cells gave rise to colonies of at least 2 morphologies expressing CK-19 or CD31 (endothelial cell marker). CD34- or c-kit-positive cells with similar properties were also isolated from normal liver. CONCLUSIONS These findings indicate that cells present in human liver that express the markers c-kit or CD34 have the capacity to differentiate into biliary epithelial cell lineage and may therefore represent human biliary epithelial progenitor cells.
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Affiliation(s)
- H A Crosby
- School of Biosciences, University of Birmingham, England.
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29
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Affiliation(s)
- H A Crosby
- School of Biosciences, University of Birmingham and Liver and Hepatobiliary Unit, University Hospital Birmingham, UK
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30
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Affiliation(s)
- A J Strain
- School of Biosciences, University of Birmingham and Liver and Hepatobiliary Unit, University Hospital, Birmingham Edgbaston, Birmingham B15 2TH, UK.
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Baumann U, Crosby HA, Ramani P, Kelly DA, Strain AJ. Expression of the stem cell factor receptor c-kit in normal and diseased pediatric liver: identification of a human hepatic progenitor cell? Hepatology 1999; 30:112-7. [PMID: 10385646 DOI: 10.1002/hep.510300140] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The stem cell factor (SCF)/c-kit ligand/receptor system has been implicated in stem (oval) cell activation following liver injury in the rat. The aim of this study was to determine the role of the SCF/c-kit system in pediatric human liver during acute and chronic liver injury. Tissue was obtained from hepatectomy specimens of patients undergoing liver transplantation for extrahepatic biliary atresia (EHBA) and fulminant hepatic failure (FHF). Specific expression of mRNA for c-kit and beta-actin was measured by ribonuclease protection and by immunohistochemistry to localize c-kit in tissue sections. Expression of c-kit was detected at relatively consistent levels in normal and cirrhotic (EHBA) livers. However, in FHF, c-kit mRNA levels were elevated in 3 of 6 specimens. Immunolocalization highlighted the presence of small numbers of c-kit-positive cells in the portal tracts of normal livers with increased numbers in cirrhotic livers. The highest c-kit staining, however, was observed in FHF, in which, in addition to the cells in the portal tracts, discrete c-kit-positive cells were also found integrated into bile ducts. Colocalization studies demonstrated some of the c-kit-positive cells to be of mast cell, leukocyte, and hematopoietic cell origin. However, there remained a subset that was also negative for these markers. The up-regulation of c-kit receptor expression in diseased livers suggests an involvement of this receptor/ligand system in hepatic repair mechanisms, and we speculate that c-kit-positive cells may represent a hepatic progenitor cell population. The origin and growth/differentiation potential of these c-kit-positive cells is under investigation.
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Affiliation(s)
- U Baumann
- The Liver Unit, Birmingham Children's Hospital, Birmingham, UK
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32
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Abstract
The existence of progenitor (stem) cells in the human liver remains a matter of debate. In rodent models of hepatocarcinogenesis and injury, oval cells proliferate in the periportal regions of the portal tracts and are suggested to derive from a stem cell compartment, because they are capable of differentiating into hepatocytes or biliary epithelial cells. In this study, the rat oval cell marker, OV-6 has been used to investigate the hypothesis that there are stem cells present in fetal and pediatric human liver. The pattern of OV-6 expression was compared with the established adult biliary cell markers human epithelial antigen-125 (HEA-125) and cytokeratin-19 (CK-19). In normal pediatric liver (n = 7), bile ducts and ductules were immunostained with CK-19 and HEA-125, whereas OV-6 staining was consistently negative. In fetal tissue (n = 10), ductal plate cells, primitive bile ducts, and hepatoblasts were stained with CK-19 and HEA-125 although only some of the ductal plate cells and hepatoblasts were OV-6 positive. In biliary atresia (n = 6) and 1, anti-trypsin deficiency (1,AT) (n = 4), CK-19 and HEA-125 immunostained ductular proliferative cells that tended to form finely anastomosing ductules, whereas OV-6 staining was found more on discrete cells confined to portal tract margins. Additionally, in diseased liver, OV-6 was strongly positive in hepatocyte lobules with greatest intensity in the periseptal regions. This widespread hepatocyte OV-6 positivity suggests that the antibody may identify cells of a less differentiated phenotype (transitional hepatocytes) that have replaced the mature cells. Therefore, it is proposed that in human liver, OV-6 is recognizing cells with a progenitor stem cell-like phenotype with the capacity to differentiate into OV-6 positive ductular cells or lobular hepatocytes.
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Affiliation(s)
- H A Crosby
- Department of Biochemistry, University of Birmingham and Liver Units, Queen Elizabeth and Children's Hospital, Birmingham, UK. H.A.Crosby.bcm.bham.ac.uk
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Crosby HA, Hubscher S, Fabris L, Joplin R, Sell S, Kelly D, Strain AJ. Immunolocalization of putative human liver progenitor cells in livers from patients with end-stage primary biliary cirrhosis and sclerosing cholangitis using the monoclonal antibody OV-6. Am J Pathol 1998; 152:771-9. [PMID: 9502419 PMCID: PMC1858380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The term oval cell describes small cells with oval nuclei that arise in the periphery of the portal tracts in rat models of hepatocarcinogenesis and injury and can differentiate into either hepatocytes or bile duct cells, ie, are bipotential. The presence of such cells in human liver is controversial. Here, immunolocalization of OV-6 and two biliary markers, cytokeratin 19 (CK-19) and human epithelial antigen 125 (HEA-125) is compared in normal adult human livers and in primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) liver sections. CK-19 and HEA-125 stained bile ducts and ductules in normal liver as well as proliferating ductular structures in diseased livers. OV-6 did not label ducts or ductules in normal liver, but in PBC and PSC stained numerous proliferating ductular and periductular cells and lobular hepatocytes. In PBC, discrete OV-6-positive cells with a mature biliary-cell-like morphology were seen integrated into some intact bile ducts as well as occasional small immature oval-like cells. In addition, in PSC, hepatocytes in regenerating lobules were also strongly stained with OV-6, and on close inspection, in both PBC and PSC, oval cells and small hepatocytes at the margins of the lobules were strongly labeled. In contrast to the rat liver, OV-6 and CK-19 staining did not always co-localize. It is proposed that the small OV-6-positive oval cells are analogous to those seen in rat models and may represent human liver progenitor cells that may differentiate into OV-6-positive ductal cells or lobular hepatocytes.
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Affiliation(s)
- H A Crosby
- Department of Biochemistry, University of Birmingham, Queen Elizabeth and Children's Hospital, United Kingdom
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Abstract
The ability of cefotaxime, ciprofloxacin, piperacillin and tobramycin to cause release of endotoxin was examined in vitro with cultures of Enterobacter cloacae and Escherichia coli. Endotoxin was measured by a quantitative limulus amoebocyte lysate assay and its presence was confirmed by silver staining of the lipopolysaccharide moiety following SDS-PAGE. The morphology of the bacteria during antibiotic exposure was examined by scanning electronmicroscopy. Cefotaxime, ciprofloxacin and piperacillin caused significant endotoxin release, correlating with their ability to affect cell-wall morphology, causing filamentation, wall breakage and cell lysis. In contrast, little endotoxin was released when bacteria were exposed to tobramycin and no morphological changes were observed when bacteria were exposed to bactericidal concentrations of this aminoglycoside. Its antimicrobial spectrum and bactericidal activity make tobramycin an appropriate agent for treatment of sepsis caused by gram-negative bacteria and its lack of propensity to elicit excessive release of endotoxin may avoid exacerbation of endotoxin-related shock in sepsis.
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Affiliation(s)
- H A Crosby
- Department of Clinical Microbiology, Queen Elizabeth Hospital, Birmingham
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35
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Bion JF, Badger I, Crosby HA, Hutchings P, Kong KL, Baker J, Hutton P, McMaster P, Buckels JA, Elliott TS. Selective decontamination of the digestive tract reduces gram-negative pulmonary colonization but not systemic endotoxemia in patients undergoing elective liver transplantation. Crit Care Med 1994; 22:40-9. [PMID: 8124972 DOI: 10.1097/00003246-199401000-00011] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
OBJECTIVE To examine the effect of selective antibiotic decontamination of the digestive tract in patients undergoing elective orthotopic liver transplantation. DESIGN Prospective, randomized, concurrent allocation to either selective decontamination or standard antibiotic prophylaxis. SETTING Operating theater and intensive care unit at a tertiary referral, university teaching hospital. PATIENTS Fifty-nine adult patients were recruited into the study and underwent liver transplantation. INTERVENTIONS Thirty-two patients were randomized to standard treatment (control group) and 27 patients were randomized to receive selective decontamination. After early deaths and exclusions, 31 controls and 21 decontamination patients were available for analysis. MEASUREMENTS AND MAIN RESULTS Portal and systemic endotoxemia, colonization and infection rates, severity of illness (organ system failures, Acute Physiology and Chronic Health Evaluation II score, Therapeutic Intervention Scoring System score), antibiotic costs, and hospital survival rates were measured. Selective decontamination significantly reduced pulmonary infections and enteric, aerobic, and Gram-negative bacillary colonization without facilitating the emergence of resistant organisms, but selective decontamination had no effect on endotoxemia or the development of organ system failures. The financial costs of the selective decontamination regimen outweighed the advantages gained from an associated reduction in antibiotic usage. CONCLUSION The failure of selective decontamination to enhance survival rates in many studies of the regimen in critically ill patients may, in part, be related to the inability of selective decontamination to abolish endotoxemia.
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Affiliation(s)
- J F Bion
- Department of Intensive Care, Queen Elizabeth Hospital, Birmingham, UK
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36
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Coles AM, Crosby HA, Pearce JH. Analysis of the human serological response to Chlamydia trachomatis 60-kDa proteins by two-dimensional electrophoresis and immunoblotting. FEMS Microbiol Lett 1991; 65:299-303. [PMID: 1916229 DOI: 10.1016/0378-1097(91)90231-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Earlier analyses of sera from humans and animals with chlamydial infections demonstrated a strong immune response to proteins of approximately 60 kDa. We have used two-dimensional (2D) electrophoresis followed by immunoblotting to more accurately define patient responses to the chlamydial 60-kDa cysteine-rich envelope protein (OMP2) and to the 57-kDa stress protein (SP) implicated in immunopathological damage. OMP2 and SP were separated on 2D gels by their distinct isoelectric points and identified by fluorography of [35S]-labelled proteins and cross-reaction with anti-mycobacterial antiserum, respectively. The majority of patients sera showed a strong reaction both to OMP2 and the SP (18/20 and 17/20 sera, respectively). Fewer sera (9/20 and 10/20 sera, respectively) reacted with two other polypeptides also present in the 60-kDa range by this analysis.
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Affiliation(s)
- A M Coles
- Microbial Molecular Genetics and Cell Biology Group, School of Biological Sciences, University of Birmingham, U.K
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37
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Badger IL, Crosby HA, Kong KL, Baker JP, Hutchings P, Elliott TS, McMaster P, Bion JF, Buckels JA. Is selective decontamination of the digestive tract beneficial in liver transplant patients? Interim results of a prospective, randomized trial. Transplant Proc 1991; 23:1460-1. [PMID: 1989265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- I L Badger
- Department of Liver Transplantation, Queen Elizabeth Hospital, Birmingham, England
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