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Shearer HL, Pace PE, Smith LM, Fineran PC, Matthews AJ, Camilli A, Dickerhof N, Hampton MB. Identification of Streptococcus pneumoniae genes associated with hypothiocyanous acid tolerance through genome-wide screening. J Bacteriol 2023; 205:e0020823. [PMID: 37791755 PMCID: PMC10601753 DOI: 10.1128/jb.00208-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 09/01/2023] [Indexed: 10/05/2023] Open
Abstract
Streptococcus pneumoniae is a commensal bacterium and invasive pathogen that causes millions of deaths worldwide. The pneumococcal vaccine offers limited protection, and the rise of antimicrobial resistance will make treatment increasingly challenging, emphasizing the need for new antipneumococcal strategies. One possibility is to target antioxidant defenses to render S. pneumoniae more susceptible to oxidants produced by the immune system. Human peroxidase enzymes will convert bacterial-derived hydrogen peroxide to hypothiocyanous acid (HOSCN) at sites of colonization and infection. Here, we used saturation transposon mutagenesis and deep sequencing to identify genes that enable S. pneumoniae to tolerate HOSCN. We identified 37 genes associated with S. pneumoniae HOSCN tolerance, including genes involved in metabolism, membrane transport, DNA repair, and oxidant detoxification. Single-gene deletion mutants of the identified antioxidant defense genes sodA, spxB, trxA, and ahpD were generated and their ability to survive HOSCN was assessed. With the exception of ΔahpD, all deletion mutants showed significantly greater sensitivity to HOSCN, validating the result of the genome-wide screen. The activity of hypothiocyanous acid reductase or glutathione reductase, known to be important for S. pneumoniae tolerance of HOSCN, was increased in three of the mutants, highlighting the compensatory potential of antioxidant systems. Double deletion of the gene encoding glutathione reductase and sodA sensitized the bacteria significantly more than single deletion. The HOSCN defense systems identified in this study may be viable targets for novel therapeutics against this deadly pathogen. IMPORTANCE Streptococcus pneumoniae is a human pathogen that causes pneumonia, bacteremia, and meningitis. Vaccination provides protection only against a quarter of the known S. pneumoniae serotypes, and the bacterium is rapidly becoming resistant to antibiotics. As such, new treatments are required. One strategy is to sensitize the bacteria to killing by the immune system. In this study, we performed a genome-wide screen to identify genes that help this bacterium resist oxidative stress exerted by the host at sites of colonization and infection. By identifying a number of critical pneumococcal defense mechanisms, our work provides novel targets for antimicrobial therapy.
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Affiliation(s)
- Heather L. Shearer
- Department of Pathology and Biomedical Science, Mātai Hāora - Centre for Redox Biology and Medicine, University of Otago Christchurch, Christchurch, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, Otago, New Zealand
| | - Paul E. Pace
- Department of Pathology and Biomedical Science, Mātai Hāora - Centre for Redox Biology and Medicine, University of Otago Christchurch, Christchurch, New Zealand
| | - Leah M. Smith
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- Genetics Otago, University of Otago, Dunedin, New Zealand
| | - Peter C. Fineran
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, Otago, New Zealand
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- Genetics Otago, University of Otago, Dunedin, New Zealand
- Bioprotection Aotearoa, University of Otago, Dunedin, New Zealand
| | - Allison J. Matthews
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Andrew Camilli
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Nina Dickerhof
- Department of Pathology and Biomedical Science, Mātai Hāora - Centre for Redox Biology and Medicine, University of Otago Christchurch, Christchurch, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, Otago, New Zealand
| | - Mark B. Hampton
- Department of Pathology and Biomedical Science, Mātai Hāora - Centre for Redox Biology and Medicine, University of Otago Christchurch, Christchurch, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, Otago, New Zealand
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2
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Hernandez-Morfa M, Olivero NB, Zappia VE, Piñas GE, Reinoso-Vizcaino NM, Cian MB, Nuñez-Fernandez M, Cortes PR, Echenique J. The oxidative stress response of Streptococcus pneumoniae: its contribution to both extracellular and intracellular survival. Front Microbiol 2023; 14:1269843. [PMID: 37789846 PMCID: PMC10543277 DOI: 10.3389/fmicb.2023.1269843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Accepted: 08/28/2023] [Indexed: 10/05/2023] Open
Abstract
Streptococcus pneumoniae is a gram-positive, aerotolerant bacterium that naturally colonizes the human nasopharynx, but also causes invasive infections and is a major cause of morbidity and mortality worldwide. This pathogen produces high levels of H2O2 to eliminate other microorganisms that belong to the microbiota of the respiratory tract. However, it also induces an oxidative stress response to survive under this stressful condition. Furthermore, this self-defense mechanism is advantageous in tolerating oxidative stress imposed by the host's immune response. This review provides a comprehensive overview of the strategies employed by the pneumococcus to survive oxidative stress. These strategies encompass the utilization of H2O2 scavengers and thioredoxins, the adaptive response to antimicrobial host oxidants, the regulation of manganese and iron homeostasis, and the intricate regulatory networks that control the stress response. Here, we have also summarized less explored aspects such as the involvement of reparation systems and polyamine metabolism. A particular emphasis is put on the role of the oxidative stress response during the transient intracellular life of Streptococcus pneumoniae, including coinfection with influenza A and the induction of antibiotic persistence in host cells.
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Affiliation(s)
- Mirelys Hernandez-Morfa
- Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Nadia B. Olivero
- Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Victoria E. Zappia
- Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - German E. Piñas
- Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Nicolas M. Reinoso-Vizcaino
- Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Melina B. Cian
- Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Mariana Nuñez-Fernandez
- Centro de Química Aplicada, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Paulo R. Cortes
- Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Jose Echenique
- Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
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3
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Glanville DG, Gazioglu O, Marra M, Tokars VL, Kushnir T, Habtom M, Croucher NJ, Nebenzahl YM, Mondragón A, Yesilkaya H, Ulijasz AT. Pneumococcal capsule expression is controlled through a conserved, distal cis-regulatory element during infection. PLoS Pathog 2023; 19:e1011035. [PMID: 36719895 PMCID: PMC9888711 DOI: 10.1371/journal.ppat.1011035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 11/29/2022] [Indexed: 02/01/2023] Open
Abstract
Streptococcus pneumoniae (the pneumococcus) is the major cause of bacterial pneumonia in the US and worldwide. Studies have shown that the differing chemical make-up between serotypes of its most important virulence factor, the capsule, can dictate disease severity. Here we demonstrate that control of capsule synthesis is also critical for infection and facilitated by two broadly conserved transcription factors, SpxR and CpsR, through a distal cis-regulatory element we name the 37-CE. Strikingly, changing only three nucleotides within this sequence is sufficient to render pneumococcus avirulent. Using in vivo and in vitro approaches, we present a model where SpxR interacts as a unique trimeric quaternary structure with the 37-CE to enable capsule repression in the airways. Considering its dramatic effect on infection, variation of the 37-CE between serotypes suggests this molecular switch could be a critical contributing factor to this pathogen's serotype-specific disease outcomes.
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Affiliation(s)
- David G. Glanville
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, United States of America
| | - Ozcan Gazioglu
- Department of Respiratory Sciences, University of Leicester, University Road, Leicester, United Kingdom
| | - Michela Marra
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, United States of America
| | - Valerie L. Tokars
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Tatyana Kushnir
- The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of The Negev, Beer-Sheva, Israel
| | - Medhanie Habtom
- Department of Respiratory Sciences, University of Leicester, University Road, Leicester, United Kingdom
| | - Nicholas J. Croucher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Sir Michael Uren Hub, Imperial College London, London, United Kingdom
| | - Yaffa Mizrachi Nebenzahl
- The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of The Negev, Beer-Sheva, Israel
| | - Alfonso Mondragón
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Hasan Yesilkaya
- Department of Respiratory Sciences, University of Leicester, University Road, Leicester, United Kingdom
| | - Andrew T. Ulijasz
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, United States of America
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4
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Zhang C, Cheng H, Han Y, Wa Y, Chen D, Guan C, Huang Y, Gu R. Transcriptome-phenotype matching analysis of how nitrogen sources influence Lacticaseibacillus rhamnosus tolerance to heat stress and oxidative stress. Microb Cell Fact 2022; 21:257. [PMID: 36510221 PMCID: PMC9746023 DOI: 10.1186/s12934-022-01985-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 12/06/2022] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Spray drying is the most cost-effective production method for lactic acid bacteria starters, but heat and oxidative stresses result in low survival rates. The heat stress and oxidative stress tolerance of Lacticaseibacillus rhamnosus cultured in tryptone-free MRS (NP-MRS) broth was much stronger than that in MRS or tryptone-free MRS broth supplemented with phenylalanine (Phe-MRS). Here, multiple transcriptome-phenotype matching was performed on cells cultured in NP-MRS, MRS and Phe-MRS broths to reveal the mechanism by which nitrogen sources influence L. rhamnosus tolerance to heat stress and oxidative stress. RESULTS Compared with cells cultured in NP-MRS broth, 83 overlapping differentially expressed genes (DEGs) were downregulated by either tryptone or phenylalanine. The overlapping DEGs were mainly classified into carbohydrate metabolism and membrane transport pathways, which are often repressed by glucose during carbon catabolite repression (CCR). In the presence of glucose, the heat stress or oxidative stress tolerance of L. rhamnosus hsryfm 1301 was not strengthened by supplementation with secondary carbohydrates. Replacing glucose with mannose, fructose or ribose improved the heat stress and oxidative stress tolerance of L. rhamnosus hsryfm 1301 (5 to 46-fold). CONCLUSIONS Alleviation of CCR might be a reason for the resistance of L. rhamnosus hsryfm 1301 to heat stress and oxidative stress in a low-nitrogen environment. The survival rate of L. rhamnosus during spray drying will hopefully be improved by relieving CCR. It is a new discovery that nitrogen sources influence CCR in L. rhamnosus.
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Affiliation(s)
- Chenchen Zhang
- College of Food Science and Engineering, Yangzhou University, 196 Huayang Xilu, Yangzhou, 225100, People's Republic of China.,Jiangsu Key Laboratory of Dairy Biotechnology and Safety Control, Yangzhou, People's Republic of China.,Jiangsu Dairy Biotechnology Engineering Research Center, Yangzhou, People's Republic of China
| | - Haohao Cheng
- College of Food Science and Engineering, Yangzhou University, 196 Huayang Xilu, Yangzhou, 225100, People's Republic of China.,Jiangsu Key Laboratory of Dairy Biotechnology and Safety Control, Yangzhou, People's Republic of China
| | - Yuemei Han
- College of Food Science and Engineering, Yangzhou University, 196 Huayang Xilu, Yangzhou, 225100, People's Republic of China.,Jiangsu Key Laboratory of Dairy Biotechnology and Safety Control, Yangzhou, People's Republic of China
| | - Yunchao Wa
- College of Food Science and Engineering, Yangzhou University, 196 Huayang Xilu, Yangzhou, 225100, People's Republic of China.,Jiangsu Key Laboratory of Dairy Biotechnology and Safety Control, Yangzhou, People's Republic of China
| | - Dawei Chen
- College of Food Science and Engineering, Yangzhou University, 196 Huayang Xilu, Yangzhou, 225100, People's Republic of China.,Jiangsu Key Laboratory of Dairy Biotechnology and Safety Control, Yangzhou, People's Republic of China
| | - Chengran Guan
- College of Food Science and Engineering, Yangzhou University, 196 Huayang Xilu, Yangzhou, 225100, People's Republic of China.,Jiangsu Key Laboratory of Dairy Biotechnology and Safety Control, Yangzhou, People's Republic of China.,Jiangsu Dairy Biotechnology Engineering Research Center, Yangzhou, People's Republic of China
| | - Yujun Huang
- College of Food Science and Engineering, Yangzhou University, 196 Huayang Xilu, Yangzhou, 225100, People's Republic of China.,Jiangsu Key Laboratory of Dairy Biotechnology and Safety Control, Yangzhou, People's Republic of China
| | - Ruixia Gu
- College of Food Science and Engineering, Yangzhou University, 196 Huayang Xilu, Yangzhou, 225100, People's Republic of China. .,Jiangsu Key Laboratory of Dairy Biotechnology and Safety Control, Yangzhou, People's Republic of China.
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5
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Defenses of multidrug resistant pathogens against reactive nitrogen species produced in infected hosts. Adv Microb Physiol 2022; 80:85-155. [PMID: 35489794 DOI: 10.1016/bs.ampbs.2022.02.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Bacterial pathogens have sophisticated systems that allow them to survive in hosts in which innate immunity is the frontline of defense. One of the substances produced by infected hosts is nitric oxide (NO) that together with its derived species leads to the so-called nitrosative stress, which has antimicrobial properties. In this review, we summarize the current knowledge on targets and protective systems that bacteria have to survive host-generated nitrosative stress. We focus on bacterial pathogens that pose serious health concerns due to the growing increase in resistance to currently available antimicrobials. We describe the role of nitrosative stress as a weapon for pathogen eradication, the detoxification enzymes, protein/DNA repair systems and metabolic strategies that contribute to limiting NO damage and ultimately allow survival of the pathogen in the host. Additionally, this systematization highlights the lack of available data for some of the most important human pathogens, a gap that urgently needs to be addressed.
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6
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Neville SL, Eijkelkamp BA, Lothian A, Paton JC, Roberts BR, Rosch JW, McDevitt CA. Cadmium stress dictates central carbon flux and alters membrane composition in Streptococcus pneumoniae. Commun Biol 2020; 3:694. [PMID: 33214631 PMCID: PMC7678824 DOI: 10.1038/s42003-020-01417-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 10/23/2020] [Indexed: 12/12/2022] Open
Abstract
Metal ion homeostasis is essential for all forms of life. However, the breadth of intracellular impacts that arise upon dysregulation of metal ion homeostasis remain to be elucidated. Here, we used cadmium, a non-physiological metal ion, to investigate how the bacterial pathogen, Streptococcus pneumoniae, resists metal ion stress and dyshomeostasis. By combining transcriptomics, metabolomics and metalloproteomics, we reveal that cadmium stress dysregulates numerous essential cellular pathways including central carbon metabolism, lipid membrane biogenesis and homeostasis, and capsule production at the transcriptional and/or functional level. Despite the breadth of cellular pathways susceptible to metal intoxication, we show that S. pneumoniae is able to maintain viability by utilizing cellular pathways that are predominately metal-independent, such as the pentose phosphate pathway to maintain energy production. Collectively, this work provides insight into the cellular processes impacted by cadmium and how resistance to metal ion toxicity is achieved in S. pneumoniae. Neville et al. investigate how Streptococcus pneumoniae mitigates metal ion stress. Despite cadmium induced dysregulation of central carbon metabolism and lipid membrane homeostasis, they find that S. pneumoniae can remain viable by selectively utilizing predominately metal-independent cellular pathways. This study provides insights into how bacteria overcome metal ion toxicity.
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Affiliation(s)
- Stephanie L Neville
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, Australia.
| | - Bart A Eijkelkamp
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia
| | - Amber Lothian
- Melbourne Dementia Research Centre, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC, Australia
| | - James C Paton
- Research Centre for Infectious Diseases, Department of Molecular and Biomedical Science, University of Adelaide, Adelaide, SA, Australia
| | - Blaine R Roberts
- Melbourne Dementia Research Centre, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC, Australia.,Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Jason W Rosch
- Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Christopher A McDevitt
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, Australia.
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7
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Ayoola MB, Nakamya MF, Shack LA, Park S, Lim J, Lee JH, Ross MK, Eoh H, Nanduri B. SP_0916 Is an Arginine Decarboxylase That Catalyzes the Synthesis of Agmatine, Which Is Critical for Capsule Biosynthesis in Streptococcus pneumoniae. Front Microbiol 2020; 11:578533. [PMID: 33072045 PMCID: PMC7531197 DOI: 10.3389/fmicb.2020.578533] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 08/24/2020] [Indexed: 12/26/2022] Open
Abstract
The global burden of invasive pneumococcal diseases, including pneumonia and sepsis, caused by Streptococcus pneumoniae, a Gram-positive bacterial pathogen, remains a major global health risk. The success of pneumococcus as a pathogen can be attributed to its ability to regulate the synthesis of capsular polysaccharide (CPS) during invasive disease. We previously reported that deletion of a putative lysine decarboxylase (LDC; ΔSP_0916) in pneumococcal serotype 4 (TIGR4) results in reduced CPS. SP_0916 locus is annotated as either an arginine or a LDC in pneumococcal genomes. In this study, by biochemical characterization of the recombinant SP_0916, we determined the substrate specificity of SP_0916 and show that it is an arginine decarboxylase (speA/ADC). We also show that deletion of the polyamine transporter (potABCD) predicted to import putrescine and spermidine results in reduced CPS, while deletion of spermidine synthase (speE) for the conversion of putrescine to spermidine had no impact on the capsule. Targeted metabolomics identified a correlation between reduced levels of agmatine and loss of capsule in ΔspeA and ΔpotABCD, while agmatine levels were comparable between the encapsulated TIGR4 and ΔspeE. Exogenous supplementation of agmatine restored CPS in both ΔpotABCD and ΔspeA. These results demonstrate that agmatine is critical for regulating the CPS, a predominant virulence factor in pneumococci.
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Affiliation(s)
- Moses B Ayoola
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States
| | - Mary F Nakamya
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States
| | - Leslie A Shack
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States
| | - Seongbin Park
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States
| | - Juhyeon Lim
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA, United States
| | - Jung Hwa Lee
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States
| | - Matthew K Ross
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States
| | - Hyungjin Eoh
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA, United States
| | - Bindu Nanduri
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States.,Institute for Genomics, Biocomputing and Biotechnology, Mississippi State University, Starkville, MS, United States
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8
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Gingerich AD, Doja F, Thomason R, Tóth E, Bradshaw JL, Douglass MV, McDaniel LS, Rada B. Oxidative killing of encapsulated and nonencapsulated Streptococcus pneumoniae by lactoperoxidase-generated hypothiocyanite. PLoS One 2020; 15:e0236389. [PMID: 32730276 PMCID: PMC7392276 DOI: 10.1371/journal.pone.0236389] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 07/06/2020] [Indexed: 01/04/2023] Open
Abstract
Streptococcus pneumoniae (Pneumococcus) infections affect millions of people worldwide, cause serious mortality and represent a major economic burden. Despite recent successes due to pneumococcal vaccination and antibiotic use, Pneumococcus remains a significant medical problem. Airway epithelial cells, the primary responders to pneumococcal infection, orchestrate an extracellular antimicrobial system consisting of lactoperoxidase (LPO), thiocyanate anion and hydrogen peroxide (H2O2). LPO oxidizes thiocyanate using H2O2 into the final product hypothiocyanite that has antimicrobial effects against a wide range of microorganisms. However, hypothiocyanite’s effect on Pneumococcus has never been studied. Our aim was to determine whether hypothiocyanite can kill S. pneumoniae. Bactericidal activity was measured in a cell-free in vitro system by determining the number of surviving pneumococci via colony forming units on agar plates, while bacteriostatic activity was assessed by measuring optical density of bacteria in liquid cultures. Our results indicate that hypothiocyanite generated by LPO exerted robust killing of both encapsulated and nonencapsulated pneumococcal strains. Killing of S. pneumoniae by a commercially available hypothiocyanite-generating product was even more pronounced than that achieved with laboratory reagents. Catalase, an H2O2 scavenger, inhibited killing of pneumococcal by hypothiocyanite under all circumstances. Furthermore, the presence of the bacterial capsule or lytA-dependent autolysis had no effect on hypothiocyanite-mediated killing of pneumococci. On the contrary, a pneumococcal mutant deficient in pyruvate oxidase (main bacterial H2O2 source) had enhanced susceptibility to hypothiocyanite compared to its wild-type strain. Overall, results shown here indicate that numerous pneumococcal strains are susceptible to LPO-generated hypothiocyanite.
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Affiliation(s)
- Aaron D. Gingerich
- Department of Infectious Diseases, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, United States of America
| | - Fayhaa Doja
- Department of Infectious Diseases, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, United States of America
| | - Rachel Thomason
- Department of Infectious Diseases, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, United States of America
| | - Eszter Tóth
- Department of Infectious Diseases, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, United States of America
| | - Jessica L. Bradshaw
- Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - Martin V. Douglass
- Department of Infectious Diseases, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, United States of America
| | - Larry S. McDaniel
- Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - Balázs Rada
- Department of Infectious Diseases, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, United States of America
- * E-mail:
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9
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Echlin H, Frank M, Rock C, Rosch JW. Role of the pyruvate metabolic network on carbohydrate metabolism and virulence in Streptococcus pneumoniae. Mol Microbiol 2020; 114:536-552. [PMID: 32495474 DOI: 10.1111/mmi.14557] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 04/27/2020] [Accepted: 05/22/2020] [Indexed: 11/30/2022]
Abstract
Streptococcus pneumoniae is a major human pathogen that must adapt to unique nutritional environments in several host niches. The pneumococcus can metabolize a range of carbohydrates that feed into glycolysis ending in pyruvate, which is catabolized by several enzymes. We investigated how the pneumococcus utilizes these enzymes to metabolize different carbohydrates and how this impacts survival in the host. Loss of ldh decreased bacterial burden in the nasopharynx and enhanced bacteremia in mice. Loss of spxB, pdhC or pfl2 decreased bacteremia and increased host survival. In glucose or galactose, loss of ldh increased capsule production, whereas loss of spxB and pdhC reduced capsule production. The pfl2 mutant exhibited reduced capsule production only in galactose. In glucose, pyruvate was metabolized primarily by LDH to generate lactate and NAD+ and by SpxB and PDHc to generate acetyl-CoA. In galactose, pyruvate metabolism was shunted toward acetyl-CoA production. The majority of acetyl-CoA generated by PFL was used to regenerate NAD+ with a subset used in capsule production, while the acetyl-CoA generated by SpxB and PDHc was utilized primarily for capsule biosynthesis. These data suggest that the pneumococcus can alter flux of pyruvate metabolism dependent on the carbohydrate present to succeed in distinct host niches.
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Affiliation(s)
- Haley Echlin
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Matthew Frank
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Charles Rock
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Jason W Rosch
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA
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10
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Pyruvate secretion by oral streptococci modulates hydrogen peroxide dependent antagonism. THE ISME JOURNAL 2020; 14:1074-1088. [PMID: 31988475 PMCID: PMC7174352 DOI: 10.1038/s41396-020-0592-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 01/14/2020] [Accepted: 01/16/2020] [Indexed: 01/28/2023]
Abstract
Many commensal oral streptococci generate H2O2 via pyruvate oxidase (SpxB) to inhibit the growth of competing bacteria like Streptococcus mutans, a major cariogenic species. In Streptococcus sanguinis SK36 (SK36) and Streptococcus gordonii DL1 (DL1), spxB expression and H2O2 release are subject to carbon catabolite repression by the catabolite control protein A (CcpA). Surprisingly, ccpA deletion mutants of SK36 and DL1 fail to inhibit S. mutans despite their production of otherwise inhibitory levels of H2O2. Using H2O2-deficient spxB deletion mutants of SK36 and DL1, it was subsequently discovered that both strains confer protection in trans to other bacteria when H2O2 is added exogenously. This protective effect depends on the direct detoxification of H2O2 by the release of pyruvate. The pyruvate dependent protective effect is also present in other spxB-encoding streptococci, such as the pneumococcus, but is missing from spxB-negative species like S. mutans. Targeted and transposon-based mutagenesis revealed Nox (putative H2O-forming NADH dehydrogenase) as an essential component required for pyruvate release and oxidative protection, while other genes such as sodA and dps play minor roles. Furthermore, pyruvate secretion is only detectable in aerobic growth conditions at biofilm-like cell densities and is responsive to CcpA-dependent catabolite control. This ability of spxB-encoding streptococci reveals a new facet of the competitive interactions between oral commensals and pathobionts and provides a mechanistic basis for the variable levels of inhibitory potential observed among H2O2-producing strains of commensal oral streptococci.
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11
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Dunne EM, Hua Y, Salaudeen R, Hossain I, Ndiaye M, Ortika BD, Mulholland EK, Hinds J, Manna S, Mackenzie GA, Satzke C. Insights into pneumococcal pneumonia using lung aspirates and nasopharyngeal swabs collected from pneumonia patients in The Gambia. J Infect Dis 2020; 225:1447-1451. [PMID: 32319524 PMCID: PMC9016440 DOI: 10.1093/infdis/jiaa186] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 04/21/2020] [Indexed: 11/20/2022] Open
Abstract
Background We investigated the pathogenesis of pneumococcal pneumonia using clinical specimens collected for pneumonia surveillance in The Gambia. Methods Lung aspirates and nasopharyngeal swabs from 31 patients were examined by culture, quantitative polymerase chain reaction (qPCR), whole genome sequencing, serotyping, and reverse-transcription qPCR. Results Five lung aspirates cultured pneumococci, with a matching strain identified in the nasopharynx. Three virulence genes including ply (pneumolysin) were upregulated >20-fold in the lung compared with the nasopharynx. Nasopharyngeal pneumococcal density was higher in pediatric pneumonia patients compared with controls (P < .0001). Conclusions Findings suggest that changes in pneumococcal gene expression occurring in the lung environment may be important in pathogenesis.
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Affiliation(s)
- Eileen M Dunne
- Infection and Immunity, Murdoch Children's Research Institute, Parkville, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, Australia
| | - Yinglei Hua
- Infection and Immunity, Murdoch Children's Research Institute, Parkville, Australia.,Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Parkville, Australia
| | - Rasheed Salaudeen
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Ilias Hossain
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Malick Ndiaye
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Belinda D Ortika
- Infection and Immunity, Murdoch Children's Research Institute, Parkville, Australia
| | - E Kim Mulholland
- Infection and Immunity, Murdoch Children's Research Institute, Parkville, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, Australia.,Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Jason Hinds
- Institute for Infection and Immunity, St. George's University of London, London, United Kingdom.,BUGS Bioscience, London Bioscience Innovation Centre, London, United Kingdom
| | - Sam Manna
- Infection and Immunity, Murdoch Children's Research Institute, Parkville, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, Australia.,Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Parkville, Australia
| | - Grant A Mackenzie
- Infection and Immunity, Murdoch Children's Research Institute, Parkville, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, Australia.,Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia.,Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Catherine Satzke
- Infection and Immunity, Murdoch Children's Research Institute, Parkville, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, Australia.,Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Parkville, Australia
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12
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Leonard A, Möhlis K, Schlüter R, Taylor E, Lalk M, Methling K. Exploring metabolic adaptation of Streptococcus pneumoniae to antibiotics. J Antibiot (Tokyo) 2020; 73:441-454. [PMID: 32210362 PMCID: PMC7292801 DOI: 10.1038/s41429-020-0296-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 01/31/2020] [Accepted: 02/09/2020] [Indexed: 02/07/2023]
Abstract
The Gram-positive bacterium Streptococcus pneumoniae is one of the common causes of community acquired pneumonia, meningitis, and otitis media. Analyzing the metabolic adaptation toward environmental stress conditions improves our understanding of its pathophysiology and its dependency on host-derived nutrients. In this study, extra- and intracellular metabolic profiles were evaluated to investigate the impact of antimicrobial compounds targeting different pathways of the metabolome of S. pneumoniae TIGR4Δcps. For the metabolomics approach, we analyzed the complex variety of metabolites by using 1H NMR, HPLC-MS, and GC–MS as different analytical techniques. Through this combination, we detected nearly 120 metabolites. For each antimicrobial compound, individual metabolic effects were detected that often comprised global biosynthetic pathways. Cefotaxime altered amino acids metabolism and carbon metabolism. The purine and pyrimidine metabolic pathways were mostly affected by moxifloxacin treatment. The combination of cefotaxime and azithromycin intensified the stress response compared with the use of the single antibiotic. However, we observed that three cell wall metabolites were altered only by treatment with the combination of the two antibiotics. Only moxifloxacin stress-induced alternation in CDP-ribitol concentration. Teixobactin-Arg10 resulted in global changes of pneumococcal metabolism. To meet the growing requirements for new antibiotics, our metabolomics approach has shown to be a promising complement to other OMICs investigations allowing insights into the mode of action of novel antimicrobial compounds.
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Affiliation(s)
- Anne Leonard
- Institute for Biochemistry, Metabolomics, University of Greifswald, Felix-Hausdorff-Str. 4, 17489, Greifswald, Germany
| | - Kevin Möhlis
- Institute for Biochemistry, Metabolomics, University of Greifswald, Felix-Hausdorff-Str. 4, 17489, Greifswald, Germany
| | - Rabea Schlüter
- Imaging Center of the Department of Biology, University of Greifswald, F.-L-Jahn-Str. 15, 17489, Greifswald, Germany
| | - Edward Taylor
- University of Lincoln, School of Life Sciences, Green Lane, LN67DL, Lincoln, England, United Kingdom
| | - Michael Lalk
- Institute for Biochemistry, Metabolomics, University of Greifswald, Felix-Hausdorff-Str. 4, 17489, Greifswald, Germany
| | - Karen Methling
- Institute for Biochemistry, Metabolomics, University of Greifswald, Felix-Hausdorff-Str. 4, 17489, Greifswald, Germany.
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13
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Davis RT, Brown PD. spoT‐mediated stringent response influences environmental and nutritional stress tolerance, biofilm formation and antimicrobial resistance inKlebsiella pneumoniae. APMIS 2019; 128:48-60. [PMID: 31693234 DOI: 10.1111/apm.13006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Accepted: 10/20/2019] [Indexed: 11/30/2022]
Affiliation(s)
- Rochell T. Davis
- Department of Basic Medical Sciences The University of the West Indies Mona Jamaica
| | - Paul D. Brown
- Department of Basic Medical Sciences The University of the West Indies Mona Jamaica
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14
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Hydrogen peroxide release by bacteria suppresses inflammasome-dependent innate immunity. Nat Commun 2019; 10:3493. [PMID: 31375698 PMCID: PMC6677825 DOI: 10.1038/s41467-019-11169-x] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 06/26/2019] [Indexed: 12/30/2022] Open
Abstract
Hydrogen peroxide (H2O2) has a major function in host-microbial interactions. Although most studies have focused on the endogenous H2O2 produced by immune cells to kill microbes, bacteria can also produce H2O2. How microbial H2O2 influences the dynamics of host-microbial interactions is unclear. Here we show that H2O2 released by Streptococcus pneumoniae inhibits inflammasomes, key components of the innate immune system, contributing to the pathogen colonization of the host. We also show that the oral commensal H2O2-producing bacteria Streptococcus oralis can block inflammasome activation. This study uncovers an unexpected role of H2O2 in immune suppression and demonstrates how, through this mechanism, bacteria might restrain the immune system to co-exist with the host. The functions of microbial hydrogen peroxide (H2O2) in host-pathogen interactions are unclear. Here, Erttmann and Gekara show that H2O2 released by Streptococcus pneumoniae inhibits inflammasomes, and thereby contributes to the pathogen’s ability to colonize the host.
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15
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Gao Y, Xu W, Dou X, Wang H, Zhang X, Yang S, Liao H, Hu X, Wang H. Mitochondrial DNA Leakage Caused by Streptococcus pneumoniae Hydrogen Peroxide Promotes Type I IFN Expression in Lung Cells. Front Microbiol 2019; 10:630. [PMID: 30984149 PMCID: PMC6447684 DOI: 10.3389/fmicb.2019.00630] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Accepted: 03/13/2019] [Indexed: 12/17/2022] Open
Abstract
Streptococcus pneumoniae (S. pn), the bacterial pathogen responsible for invasive pneumococcal diseases, is capable of producing substantial amounts of hydrogen peroxide. However, the impact of S. pn-secreted hydrogen peroxide (H2O2) on the host immune processes is not completely understood. Here, we demonstrated that S. pn-secreted H2O2 caused mitochondrial damage and severe histopathological damage in mouse lung tissue. Additionally, S. pn-secreted H2O2 caused not only oxidative damage to mitochondrial deoxyribonucleic acid (mtDNA), but also a reduction in the mtDNA content in alveolar epithelia cells. This resulted in the release of mtDNA into the cytoplasm, which subsequently induced type I interferons (IFN-I) expression. We also determined that stimulator of interferon genes (STING) signaling was probably involved in S. pn H2O2-inducing IFN-I expression in response to mtDNA damaged by S. pn-secreted H2O2. In conclusion, our study demonstrated that H2O2 produced by S. pn resulted in mtDNA leakage from damaged mitochondria and IFN-I production in alveolar epithelia cells, and STING may be required in this process, and this is a novel mitochondrial damage mechanism by which S. pn potentiates the IFN-I cascade in S. pn infection.
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Affiliation(s)
- Yue Gao
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China.,School of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Wenchun Xu
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China.,School of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Xiaoyun Dou
- Institute of Life Sciences, Chongqing Medical University, Chongqing, China
| | - Hong Wang
- Institute of Life Sciences, Chongqing Medical University, Chongqing, China
| | - Xuemei Zhang
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China.,School of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Shenghui Yang
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China.,School of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Hongyi Liao
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China.,School of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Xuexue Hu
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China.,School of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | - Hong Wang
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China.,School of Laboratory Medicine, Chongqing Medical University, Chongqing, China
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16
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Engholm DH, Kilian M, Goodsell DS, Andersen ES, Kjærgaard RS. A visual review of the human pathogen Streptococcus pneumoniae. FEMS Microbiol Rev 2018; 41:854-879. [PMID: 29029129 DOI: 10.1093/femsre/fux037] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 09/04/2017] [Indexed: 11/12/2022] Open
Abstract
Being the principal causative agent of bacterial pneumonia, otitis media, meningitis and septicemia, the bacterium Streptococcus pneumoniae is a major global health problem. To highlight the molecular basis of this problem, we have portrayed essential biological processes of the pneumococcal life cycle in eight watercolor paintings. The paintings are done to a consistent nanometer scale based on currently available data from structural biology and proteomics. In this review article, the paintings are used to provide a visual review of protein synthesis, carbohydrate metabolism, cell wall synthesis, cell division, teichoic acid synthesis, virulence, transformation and pilus synthesis based on the available scientific literature within the field of pneumococcal biology. Visualization of the molecular details of these processes reveals several scientific questions about how molecular components of the pneumococcal cell are organized to allow biological function to take place. By the presentation of this visual review, we intend to stimulate scientific discussion, aid in the generation of scientific hypotheses and increase public awareness. A narrated video describing the biological processes in the context of a whole-cell illustration accompany this article.
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Affiliation(s)
- Ditte Høyer Engholm
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
| | - Mogens Kilian
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark
| | - David S Goodsell
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.,Rutgers, the State University of New Jersey, NJ 08901, USA
| | - Ebbe Sloth Andersen
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark.,Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus, Denmark
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17
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Carvalho SM, Kloosterman TG, Manzoor I, Caldas J, Vinga S, Martinussen J, Saraiva LM, Kuipers OP, Neves AR. Interplay Between Capsule Expression and Uracil Metabolism in Streptococcus pneumoniae D39. Front Microbiol 2018; 9:321. [PMID: 29599757 PMCID: PMC5863508 DOI: 10.3389/fmicb.2018.00321] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 02/09/2018] [Indexed: 11/13/2022] Open
Abstract
Pyrimidine nucleotides play an important role in the biosynthesis of activated nucleotide sugars (NDP-sugars). NDP-sugars are the precursors of structural polysaccharides in bacteria, including capsule, which is a major virulence factor of the human pathogen S. pneumoniae. In this work, we identified a spontaneous non-reversible mutant of strain D39 that displayed a non-producing capsule phenotype. Whole-genome sequencing analysis of this mutant revealed several non-synonymous single base modifications, including in genes of the de novo synthesis of pyrimidines and in the -10 box of capsule operon promoter (Pcps). By directed mutagenesis we showed that the point mutation in Pcps was solely responsible for the drastic decrease in capsule expression. We also demonstrated that D39 subjected to uracil deprivation shows increased biomass and decreased Pcps activity and capsule amounts. Importantly, Pcps expression is further decreased by mutating the first gene of the de novo synthesis of pyrimidines, carA. In contrast, the absence of uracil from the culture medium showed no effect on the spontaneous mutant strain. Co-cultivation of the wild-type and the mutant strain indicated a competitive advantage of the spontaneous mutant (non-producing capsule) in medium devoid of uracil. We propose a model in that uracil may act as a signal for the production of different capsule amounts in S. pneumoniae.
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Affiliation(s)
- Sandra M Carvalho
- Instituto de Tecnologia Química e Biológica NOVA, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Tomas G Kloosterman
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, Netherlands
| | - Irfan Manzoor
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, Netherlands
| | - José Caldas
- Instituto de Engenharia de Sistemas e Computadores, Investigação e Desenvolvimento (INESC-ID), Lisbon, Portugal
| | - Susana Vinga
- IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | - Jan Martinussen
- DTU Systems Biology, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Lígia M Saraiva
- Instituto de Tecnologia Química e Biológica NOVA, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Oscar P Kuipers
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, Netherlands
| | - Ana R Neves
- Instituto de Tecnologia Química e Biológica NOVA, Universidade Nova de Lisboa, Oeiras, Portugal
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18
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Liu YT, Pan Y, Lai F, Yin XF, Ge R, He QY, Sun X. Comprehensive analysis of the lysine acetylome and its potential regulatory roles in the virulence of Streptococcus pneumoniae. J Proteomics 2018; 176:46-55. [DOI: 10.1016/j.jprot.2018.01.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 01/18/2018] [Accepted: 01/25/2018] [Indexed: 12/28/2022]
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19
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Nakamya MF, Ayoola MB, Park S, Shack LA, Swiatlo E, Nanduri B. The Role of Cadaverine Synthesis on Pneumococcal Capsule and Protein Expression. Med Sci (Basel) 2018; 6:E8. [PMID: 29351189 PMCID: PMC5872165 DOI: 10.3390/medsci6010008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2017] [Revised: 01/07/2018] [Accepted: 01/09/2018] [Indexed: 12/25/2022] Open
Abstract
Invasive infections caused by Streptococcus pneumoniae, a commensal in the nasopharynx, pose significant risk to human health. Limited serotype coverage by the available polysaccharide-based conjugate vaccines coupled with increasing incidence of antibiotic resistance complicates therapeutic strategies. Bacterial physiology and metabolism that allows pathogens to adapt to the host are a promising avenue for the discovery of novel therapeutics. Intracellular polyamine concentrations are tightly regulated by biosynthesis, transport and degradation. We previously reported that deletion of cadA, a gene that encodes for lysine decarboxylase, an enzyme that catalyzes cadaverine synthesis results in an attenuated phenotype. Here, we report the impact of cadA deletion on pneumococcal capsule and protein expression. Our data show that genes for polyamine biosynthesis and transport are downregulated in ∆cadA. Immunoblot assays show reduced capsule in ∆cadA. Reduced capsule synthesis could be due to reduced transcription and availability of precursors for synthesis. The capsule is the predominant virulence factor in pneumococci and is critical for evading opsonophagocytosis and its loss in ∆cadA could explain the reported attenuation in vivo. Results from this study show that capsule synthesis in pneumococci is regulated by polyamine metabolism, which can be targeted for developing novel therapies.
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Affiliation(s)
- Mary F Nakamya
- Department of Basic Sciences, College of Veterinary Medicine, P.O. Box 6100, Mississippi State, MS 39762, USA.
| | - Moses B Ayoola
- Department of Basic Sciences, College of Veterinary Medicine, P.O. Box 6100, Mississippi State, MS 39762, USA.
| | - Seongbin Park
- Department of Basic Sciences, College of Veterinary Medicine, P.O. Box 6100, Mississippi State, MS 39762, USA.
| | - Leslie A Shack
- Department of Basic Sciences, College of Veterinary Medicine, P.O. Box 6100, Mississippi State, MS 39762, USA.
| | - Edwin Swiatlo
- Section of Infectious Diseases, Southeast Louisiana Veterans Health Care System, New Orleans, LA 70112, USA.
| | - Bindu Nanduri
- Department of Basic Sciences, College of Veterinary Medicine, P.O. Box 6100, Mississippi State, MS 39762, USA.
- Institute for Genomics, Biocomputing & Biotechnology, Mississippi State University, Mississippi State, MS 39762, USA.
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20
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Cell Invasion and Pyruvate Oxidase-Derived H 2O 2 Are Critical for Streptococcus pneumoniae-Mediated Cardiomyocyte Killing. Infect Immun 2017; 86:IAI.00569-17. [PMID: 29061707 DOI: 10.1128/iai.00569-17] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 10/17/2017] [Indexed: 01/19/2023] Open
Abstract
Streptococcus pneumoniae (the pneumococcus) is the leading cause of community-acquired pneumonia and is now recognized to be a direct contributor to adverse acute cardiac events. During invasive pneumococcal disease, S. pneumoniae can gain access to the myocardium, kill cardiomyocytes, and form bacterium-filled "microlesions" causing considerable acute and long-lasting cardiac damage. While the molecular mechanisms responsible for bacterial translocation into the heart have been elucidated, the initial interactions of heart-invaded S. pneumoniae with cardiomyocytes remain unclear. In this study, we used a model of low multiplicity of S. pneumoniae infection with HL-1 mouse cardiomyocytes to investigate these early events. Using adhesion/invasion assays and immunofluorescent and transmission electron microscopy, we showed that S. pneumoniae rapidly adhered to and invaded cardiomyocytes. What is more, pneumococci existed as intravacuolar bacteria or escaped into the cytoplasm. Pulse-chase assays with BrdU confirmed intracellular replication of pneumococci within HL-1 cells. Using endocytosis inhibitors, bacterial isogenic mutants, and neutralizing antibodies against host proteins recognized by S. pneumoniae adhesins, we showed that S. pneumoniae uptake by cardiomyocytes is not through the well-studied canonical interactions identified for vascular endothelial cells. Indeed, S. pneumoniae invasion of HL-1 cells occurred through clathrin-mediated endocytosis (CME) and independently of choline binding protein A (CbpA)/laminin receptor, CbpA/polymeric immunoglobulin receptor, or cell wall phosphorylcholine/platelet-activating factor receptor. Subsequently, we determined that pneumolysin and streptococcal pyruvate oxidase-derived H2O2 production were required for cardiomyocyte killing. Finally, we showed that this cytotoxicity could be abrogated using CME inhibitors or antioxidants, attesting to intracellular replication of S. pneumoniae as a key first step in pneumococcal pathogenesis within the heart.
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21
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Chai MH, Weiland F, Harvey RM, Hoffmann P, Ogunniyi AD, Paton JC. Proteomic comparisons of opaque and transparent variants of Streptococcus pneumoniae by two dimensional-differential gel electrophoresis. Sci Rep 2017; 7:2453. [PMID: 28550292 PMCID: PMC5446427 DOI: 10.1038/s41598-017-02465-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 04/11/2017] [Indexed: 11/09/2022] Open
Abstract
Streptococcus pneumoniae (the pneumococcus) is a human pathogen, accounting for massive global morbidity and mortality. Although asymptomatic colonization of the nasopharynx almost invariably precedes disease, the critical determinants enabling pneumococcal progression from this niche to cause invasive disease are poorly understood. One mechanism proposed to be central to this transition involves opacity phase variation, whereby pneumococci harvested from the nasopharynx are typically transparent, while those simultaneously harvested from the blood are opaque. Here, we used two dimensional-differential gel electrophoresis (2D-DIGE) to compare protein expression profiles of transparent and opaque variants of 3 pneumococcal strains, D39 (serotype 2), WCH43 (serotype 4) and WCH16 (serotype 6A) in vitro. One spot comprising a mixture of capsular polysaccharide biosynthesis protein and other proteins was significantly up-regulated in the opaque phenotype in all 3 strains; other proteins were differentially regulated in a strain-specific manner. We conclude that pneumococcal phase variation is a complex and multifactorial process leading to strain-specific pathogenicity.
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Affiliation(s)
- Melissa H Chai
- Research Centre for Infectious Diseases, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, 5005, Australia
| | - Florian Weiland
- Adelaide Proteomics Centre, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, 5005, Australia.,Institute for Photonics and Advanced Sensing (IPAS), The University of Adelaide, Adelaide, South Australia, 5005, Australia.,Medical Research Council Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, United Kingdom
| | - Richard M Harvey
- Research Centre for Infectious Diseases, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, 5005, Australia
| | - Peter Hoffmann
- Adelaide Proteomics Centre, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, 5005, Australia.,Institute for Photonics and Advanced Sensing (IPAS), The University of Adelaide, Adelaide, South Australia, 5005, Australia
| | - Abiodun D Ogunniyi
- Research Centre for Infectious Diseases, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, 5005, Australia. .,Australian Centre for Antimicrobial Resistance Ecology, School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, South Australia, 5371, Australia.
| | - James C Paton
- Research Centre for Infectious Diseases, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, 5005, Australia
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22
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Sumioka R, Nakata M, Okahashi N, Li Y, Wada S, Yamaguchi M, Sumitomo T, Hayashi M, Kawabata S. Streptococcus sanguinis induces neutrophil cell death by production of hydrogen peroxide. PLoS One 2017; 12:e0172223. [PMID: 28222125 PMCID: PMC5319702 DOI: 10.1371/journal.pone.0172223] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 02/01/2017] [Indexed: 11/18/2022] Open
Abstract
Streptococcus is the dominant bacterial genus in the human oral cavity and a leading cause of infective endocarditis. Streptococcus sanguinis belongs to the mitis group of streptococci and produces hydrogen peroxide (H2O2) by the action of SpxB, a pyruvate oxidase. In this study, we investigated the involvement of SpxB in survival of S. sanguinis in human blood and whether bacterial H2O2 exhibits cytotoxicity against human neutrophils. Results of a bactericidal test with human whole blood revealed that the spxB mutation in S. sanguinis is detrimental to its survival in blood. When S. sanguinis strains were exposed to isolated neutrophils, the bacterial survival rate was significantly decreased by spxB deletion. Furthermore, human neutrophils exposed to the S. sanguinis wild-type strain, in contrast to those exposed to an spxB mutant strain, underwent cell death with chromatin de-condensation and release of web-like extracellular DNA, reflecting induction of neutrophil extracellular traps (NETs). Since reactive oxygen species-mediated NET induction requires citrullination of arginine residues in histone proteins and subsequent chromatin de-condensation, we examined citrullination levels of histone in infected neutrophils. It is important to note that the citrullinated histone H3 was readily detected in neutrophils infected with the wild-type strain, as compared to infection with the spxB mutant strain. Moreover, decomposition of streptococcal H2O2 with catalase reduced NET induction. These results suggest that H2O2 produced by S. sanguinis provokes cell death of neutrophils and NET formation, thus potentially affecting bacterial survival in the bloodstream.
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Affiliation(s)
- Ryuichi Sumioka
- Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan
- Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan
| | - Masanobu Nakata
- Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan
- * E-mail:
| | - Nobuo Okahashi
- Center for Frontier Oral Science, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan
| | - Yixuan Li
- Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan
| | - Satoshi Wada
- Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan
| | - Masaya Yamaguchi
- Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan
| | - Tomoko Sumitomo
- Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan
| | - Mikako Hayashi
- Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan
| | - Shigetada Kawabata
- Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan
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Biological and Chemical Adaptation to Endogenous Hydrogen Peroxide Production in Streptococcus pneumoniae D39. mSphere 2017; 2:mSphere00291-16. [PMID: 28070562 PMCID: PMC5214746 DOI: 10.1128/msphere.00291-16] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 12/04/2016] [Indexed: 12/29/2022] Open
Abstract
Adaptation to endogenous oxidative stress is an integral aspect of Streptococcus pneumoniae colonization and virulence. In this work, we identify key transcriptomic and proteomic features of the pneumococcal endogenous oxidative stress response. The thiol peroxidase TpxD plays a critical role in adaptation to endogenous H2O2 and serves to limit protein sulfenylation of glycolytic, capsule, and nucleotide biosynthesis enzymes in S. pneumoniae. The catalase-negative, facultative anaerobe Streptococcus pneumoniae D39 is naturally resistant to hydrogen peroxide (H2O2) produced endogenously by pyruvate oxidase (SpxB). Here, we investigate the adaptive response to endogenously produced H2O2. We show that lactate oxidase, which converts lactate to pyruvate, positively impacts pyruvate flux through SpxB and that ΔlctO mutants produce significantly lower H2O2. In addition, both the SpxB pathway and a candidate pyruvate dehydrogenase complex (PDHC) pathway contribute to acetyl coenzyme A (acetyl-CoA) production during aerobic growth, and the pyruvate format lyase (PFL) pathway is the major acetyl-CoA pathway during anaerobic growth. Microarray analysis of the D39 strain cultured under aerobic versus strict anaerobic conditions shows upregulation of spxB, a gene encoding a rhodanese-like protein (locus tag spd0091), tpxD, sodA, piuB, piuD, and an Fe-S protein biogenesis operon under H2O2-producing conditions. Proteome profiling of H2O2-induced sulfenylation reveals that sulfenylation levels correlate with cellular H2O2 production, with endogenous sulfenylation of ≈50 proteins. Deletion of tpxD increases cellular sulfenylation 5-fold and has an inhibitory effect on ATP generation. Two major targets of protein sulfenylation are glyceraldehyde-3-phosphate dehydrogenase (GapA) and SpxB itself, but targets also include pyruvate kinase, LctO, AdhE, and acetate kinase (AckA). Sulfenylation of GapA is inhibitory, while the effect on SpxB activity is negligible. Strikingly, four enzymes of capsular polysaccharide biosynthesis are sulfenylated, as are enzymes associated with nucleotide biosynthesis via ribulose-5-phosphate. We propose that LctO/SpxB-generated H2O2 functions as a signaling molecule to downregulate capsule production and drive altered flux through sugar utilization pathways. IMPORTANCE Adaptation to endogenous oxidative stress is an integral aspect of Streptococcus pneumoniae colonization and virulence. In this work, we identify key transcriptomic and proteomic features of the pneumococcal endogenous oxidative stress response. The thiol peroxidase TpxD plays a critical role in adaptation to endogenous H2O2 and serves to limit protein sulfenylation of glycolytic, capsule, and nucleotide biosynthesis enzymes in S. pneumoniae.
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Echlin H, Frank MW, Iverson A, Chang TC, Johnson MDL, Rock CO, Rosch JW. Pyruvate Oxidase as a Critical Link between Metabolism and Capsule Biosynthesis in Streptococcus pneumoniae. PLoS Pathog 2016; 12:e1005951. [PMID: 27760231 PMCID: PMC5070856 DOI: 10.1371/journal.ppat.1005951] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Accepted: 09/23/2016] [Indexed: 01/12/2023] Open
Abstract
The pneumococcus is one of the most prodigious producers of hydrogen peroxide amongst bacterial pathogens. Hydrogen peroxide production by the pneumococcus has been implicated in antibiotic synergism, competition between other bacterial colonizers of the nasopharynx, and damage to epithelial cells. However, the role during invasive disease has been less clear with mutants defective in hydrogen peroxide production demonstrating both attenuation and heightened invasive disease capacity depending upon strain and serotype background. This work resolves these conflicting observations by demonstrating that the main hydrogen peroxide producing enzyme of the pneumococcus, SpxB, is required for capsule formation in a strain dependent manner. Capsule production by strains harboring capsules with acetylated sugars was dependent upon the presence of spxB while capsule production in serotypes lacking such linkages were not. The spxB mutant had significantly lower steady-state cellular levels of acetyl-CoA, suggesting that loss of capsule arises from dysregulation of this intermediary metabolite. This conclusion is corroborated by deletion of pdhC, which also resulted in lower steady-state acetyl-CoA levels and phenocopied the capsule expression profile of the spxB mutant. Capsule and acetyl-CoA levels were restored in the spxB and lctO (lactate oxidase) double mutant, supporting the connection between central metabolism and capsule formation. Taken together, these data show that the defect in pathogenesis in the spxB mutant is due to a metabolic imbalance that attenuates capsule formation and not to reduced hydrogen peroxide formation. The pneumococcus polysaccharide capsule is one of the most critical virulence determinants produced by this major human pathogen. The pneumococcus also produces prodigious amounts of hydrogen peroxide via the enzymatic reaction catalyzed by pyruvate oxidase, SpxB. Deletion of spxB resulted in the loss of surface polysaccharide capsule production in a serotype dependent manner with a mirrored effect on the virulence of the mutants. We observed that deletion of spxB reduced the steady-state levels of acetyl-CoA, a key metabolic intermediate in peptidoglycan, fatty acid biosynthesis, and in capsule biosynthesis in a subset of serotypes. These data suggest that the defect in capsule production was due to altered metabolism that results in reduced acetyl-CoA availability. Corroborating these data, we found that capsule biosynthesis was impaired upon loss of PDHC, an additional metabolic enzyme that generates acetyl-CoA. These data reveal a critical link between pneumococcal metabolism and capsule biosynthesis as well as provide a striking example of how a virulence gene can have a differential contribution to pathogenesis dependent upon strain background.
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Affiliation(s)
- Haley Echlin
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Matthew W. Frank
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Amy Iverson
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Ti-Cheng Chang
- Department of Computational Biology, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Michael D. L. Johnson
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Charles O. Rock
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Jason W. Rosch
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
- * E-mail:
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Epigenetic Switch Driven by DNA Inversions Dictates Phase Variation in Streptococcus pneumoniae. PLoS Pathog 2016; 12:e1005762. [PMID: 27427949 PMCID: PMC4948785 DOI: 10.1371/journal.ppat.1005762] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Accepted: 06/20/2016] [Indexed: 02/05/2023] Open
Abstract
DNA methylation is an important epigenetic mechanism for phenotypic diversification in all forms of life. We previously described remarkable cell-to-cell heterogeneity in epigenetic pattern within a clonal population of Streptococcus pneumoniae, a leading human pathogen. We here report that the epigenetic diversity is caused by extensive DNA inversions among hsdSA,hsdSB, and hsdSC, three methyltransferase hsdS genes in the Spn556II type-I restriction modification (R-M) locus. Because hsdSA encodes the sequence recognition subunit of this type-I R-M DNA methyltransferase, these site-specific recombinations generate pneumococcal cells with variable HsdSA alleles and thereby diverse genome methylation patterns. Most importantly, the DNA methylation pattern specified by the HsdSA1 allele leads to the formation of opaque colonies, whereas the pneumococci lacking HsdSA1 produce transparent colonies. Furthermore, this HsdSA1-dependent phase variation requires intact DNA methylase activity encoded by hsdM in the Spn556II (renamed colony opacity determinant or cod) locus. Thus, the DNA inversion-driven ON/OFF switch of the hsdSA1 allele in the cod locus and resulting epigenetic switch dictate the phase variation between the opaque and transparent phenotypes. Phase variation has been well documented for its importance in pneumococcal carriage and invasive infection, but its molecular basis remains unclear. Our work has discovered a novel epigenetic cause for this significant pathobiology phenomenon in S. pneumoniae. Lastly, our findings broadly represents a significant advancement in our understanding of bacterial R-M systems and their potential in shaping epigenetic and phenotypic diversity of the prokaryotic organisms because similar site-specific recombination systems widely exist in many archaeal and bacterial species. DNA methylation is a well-known epigenetic mechanism for phenotypic diversification in all forms of life. This study reports our discovery that the Spn556II type-I RM locus in human pathogen Streptococcus pneumoniae undergoes extensive DNA inversions among three homologous DNA methyltransferase genes. These site-specific recombinations generate subpopulations of progeny cells with dramatic epigenetic and phenotypic differences. This is exemplified by the striking differences in colony morphology among the pneumococcal variants that carried different allelic variants of the methyltransferase genes. Phase variation has been well documented for its importance in pneumococcal pathogenesis, but it is currently unknown how this phenotypic switch occurs at the molecular level. This work has thus discovered an epigenetic cause for pneumococcal phase variation. Our findings have a broad implication on the epigenetic and phenotypic diversification in prokaryotic organisms because similar DNA rearrangement systems also exist in many archaeal and bacterial species.
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Abstract
Streptococcus pneumoniae is an opportunistic pathogen globally associated with significant morbidity and mortality. It is capable of causing a wide range of diseases including sinusitis, conjunctivitis, otitis media, pneumonia, bacteraemia, sepsis, and meningitis. While its capsular polysaccharide is indispensible for invasive disease, and opsonising antibodies against the capsule are the basis for the current vaccines, a long history of biomedical research indicates that other components of this Gram-positive bacterium are also critical for virulence. Herein we review the contribution of pneumococcal virulence determinants to survival and persistence in the context of distinct anatomical sites. We discuss how these determinants allow the pneumococcus to evade mucociliary clearance during colonisation, establish lower respiratory tract infection, resist complement deposition and opsonophagocytosis in the bloodstream, and invade secondary tissues such as the central nervous system leading to meningitis. We do so in a manner that highlights both the critical role of the capsular polysaccharide and the accompanying and necessary protein determinants. Understanding the complex interplay between host and pathogen is necessary to find new ways to prevent pneumococcal infection. This review is an attempt to do so with consideration for the latest research findings.
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27
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Abstract
Streptococcus pneumoniae (the pneumococcus) is an important human pathogen. Its virulence is largely due to its polysaccharide capsule, which shields it from the host immune system, and because of this, the capsule has been extensively studied. Studies of the capsule led to the identification of DNA as the genetic material, identification of many different capsular serotypes, and identification of the serotype-specific nature of protection by adaptive immunity. Recent studies have led to the determination of capsular polysaccharide structures for many serotypes using advanced analytical technologies, complete elucidation of genetic basis for the capsular types, and the development of highly effective pneumococcal conjugate vaccines. Conjugate vaccine use has altered the serotype distribution by either serotype replacement or switching, and this has increased the need to serotype pneumococci. Due to great advances in molecular technologies and our understanding of the pneumococcal genome, molecular approaches have become powerful tools to predict pneumococcal serotypes. In addition, more-precise and -efficient serotyping methods that directly detect polysaccharide structures are emerging. These improvements in our capabilities will greatly enhance future investigations of pneumococcal epidemiology and diseases and the biology of colonization and innate immunity to pneumococcal capsules.
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Assessing the Metabolic Diversity of Streptococcus from a Protein Domain Point of View. PLoS One 2015; 10:e0137908. [PMID: 26366735 PMCID: PMC4569324 DOI: 10.1371/journal.pone.0137908] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 08/22/2015] [Indexed: 01/17/2023] Open
Abstract
Understanding the diversity and robustness of the metabolism of bacteria is fundamental for understanding how bacteria evolve and adapt to different environments. In this study, we characterised 121 Streptococcus strains and studied metabolic diversity from a protein domain perspective. Metabolic pathways were described in terms of the promiscuity of domains participating in metabolic pathways that were inferred to be functional. Promiscuity was defined by adapting existing measures based on domain abundance and versatility. The approach proved to be successful in capturing bacterial metabolic flexibility and species diversity, indicating that it can be described in terms of reuse and sharing functional domains in different proteins involved in metabolic activity. Additionally, we showed striking differences among metabolic organisation of the pathogenic serotype 2 Streptococcus suis and other strains.
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Tikhomirova A, Trappetti C, Paton JC, Kidd SP. The outcome of H. influenzae and S. pneumoniae inter-species interactions depends on pH, nutrient availability and growth phase. Int J Med Microbiol 2015; 305:881-92. [PMID: 26481153 DOI: 10.1016/j.ijmm.2015.09.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 09/07/2015] [Accepted: 09/10/2015] [Indexed: 01/16/2023] Open
Abstract
Haemophilus influenzae and Streptococcus pneumoniae exist together as common commensals of the healthy human nasopharynx, but both are important aetiological agents of different diseases, including the paediatric disease otitis media. It was recently shown that the formation of a multispecies biofilm of H. influenzae and S. pneumoniae is the cause of chronic forms of otitis media. However, the interactions between the two species are not clearly defined. Using a defined and kinetic analysis, our study has shown that while co-existence of the two species occurs, S. pneumoniae is also able to convert H. influenzae to a non-culturable state. We determined that this process was dependent on growth phase and pH. To analyse the H. influenzae/S. pneumoniae interactions in more depth, we investigated the growth and transcriptional profile in a pH-defined batch culture model, as well as in a growth phase independent flow cell system. Transcriptomics has shown that there are changes in gene expression in each of the species when grown in co-culture, intriguingly inducing the S. pneumoniae bacteriocin transport genes, and phage-associated genes in both species. Importantly, we have shown vast changes in gene expression in a group of S. pneumoniae metabolic genes, including those encoding lactose utilisation, glycerol utilisation and sugar transport proteins; we have shown that the expression of these genes depends not only on the presence of H. influenzae, but also on the growth system utilised.
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Affiliation(s)
- Alexandra Tikhomirova
- Research Centre for Infectious Disease, School of Biological Sciences, The University of Adelaide, Adelaide, Australia
| | - Claudia Trappetti
- Research Centre for Infectious Disease, School of Biological Sciences, The University of Adelaide, Adelaide, Australia
| | - James C Paton
- Research Centre for Infectious Disease, School of Biological Sciences, The University of Adelaide, Adelaide, Australia
| | - Stephen P Kidd
- Research Centre for Infectious Disease, School of Biological Sciences, The University of Adelaide, Adelaide, Australia.
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30
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Marx P, Meiers M, Brückner R. Activity of the response regulator CiaR in mutants of Streptococcus pneumoniae R6 altered in acetyl phosphate production. Front Microbiol 2015; 5:772. [PMID: 25642214 PMCID: PMC4295557 DOI: 10.3389/fmicb.2014.00772] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 12/17/2014] [Indexed: 11/25/2022] Open
Abstract
The two-component regulatory system (TCS) CiaRH of Streptococcus pneumoniae is implicated in competence, ß-lactam resistance, maintenance of cell integrity, bacteriocin production, host colonization, and virulence. Depending on the growth conditions, CiaR can be highly active in the absence of its cognate kinase CiaH, although phosphorylation of CiaR is required for DNA binding and gene regulation. To test the possibility that acetyl phosphate (AcP) could be the alternative phosphodonor, genes involved in pyruvate metabolism were disrupted to alter cellular levels of acetyl phosphate. Inactivating the genes of pyruvate oxidase SpxB, phosphotransacetylase Pta, and acetate kinase AckA, resulted in very low AcP levels and in strongly reduced CiaR-mediated gene expression in CiaH-deficient strains. Therefore, alternative phosphorylation of CiaR appears to proceed via AcP. The AcP effect on CiaR is not detected in strains with CiaH. Attempts to obtain elevated AcP by preventing its degradation by acetate kinase AckA, were not successful in CiaH-deficient strains with a functional SpxB, the most important enzyme for AcP production in S. pneumoniae. The ciaH-spxB-ackA mutant producing intermediate amounts of AcP could be constructed and showed a promoter activation, which was much higher than expected. Since activation was dependent on AcP, it can apparently be used more efficiently for CiaR phosphorylation in the absence of AckA. Therefore, high AcP levels in the absence of CiaH and AckA may cause extreme overexpression of the CiaR regulon leading to synthetic lethality. AckA is also involved in a regulatory response, which is mediated by CiaH. Addition of acetate to the growth medium switch CiaH from kinase to phosphatase. This switch is lost in the absence of AckA indicating metabolism of acetate is required, which starts with the production of AcP by AckA. Therefore, AckA plays a special regulatory role in the control of the CiaRH TCS.
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Affiliation(s)
- Patrick Marx
- Department of Microbiology, University of Kaiserslautern Kaiserslautern, Germany
| | - Marina Meiers
- Department of Microbiology, University of Kaiserslautern Kaiserslautern, Germany
| | - Reinhold Brückner
- Department of Microbiology, University of Kaiserslautern Kaiserslautern, Germany
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31
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Ramirez M. Streptococcus pneumoniae. MOLECULAR MEDICAL MICROBIOLOGY 2015:1529-1546. [DOI: 10.1016/b978-0-12-397169-2.00086-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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32
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Andam CP, Hanage WP. Mechanisms of genome evolution of Streptococcus. INFECTION GENETICS AND EVOLUTION 2014; 33:334-42. [PMID: 25461843 DOI: 10.1016/j.meegid.2014.11.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 11/05/2014] [Accepted: 11/07/2014] [Indexed: 10/24/2022]
Abstract
The genus Streptococcus contains 104 recognized species, many of which are associated with human or animal hosts. A globally prevalent human pathogen in this group is Streptococcus pneumoniae (the pneumococcus). While being a common resident of the upper respiratory tract, it is also a major cause of otitis media, pneumonia, bacteremia and meningitis, accounting for a high burden of morbidity and mortality worldwide. Recent findings demonstrate the importance of recombination and selection in driving the population dynamics and evolution of different pneumococcal lineages, allowing them to successfully evade the impacts of selective pressures such as vaccination and antibiotic treatment. We highlight the ability of pneumococci to respond to these pressures through processes including serotype replacement, capsular switching and horizontal gene transfer (HGT) of antibiotic resistance genes. The challenge in controlling this pathogen also lies in the exceptional genetic and phenotypic variation among different pneumococcal lineages, particularly in terms of their pathogenicity and resistance to current therapeutic strategies. The widespread use of pneumococcal conjugate vaccines, which target only a small subset of the more than 90 pneumococcal serotypes, provides us with a unique opportunity to elucidate how the processes of selection and recombination interact to generate a remarkable level of plasticity and heterogeneity in the pneumococcal genome. These processes also play an important role in the emergence and spread of multi-resistant strains, which continues to pose a challenge in disease control and/or eradication. The application of population of genomic approaches at different spatial and temporal scales will help improve strategies to control this global pathogen, and potentially other pathogenic streptococci.
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Affiliation(s)
- Cheryl P Andam
- Department of Epidemiology, Harvard School of Public Health, Boston, MA 02115, USA
| | - William P Hanage
- Department of Epidemiology, Harvard School of Public Health, Boston, MA 02115, USA.
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Lactate dehydrogenase is the key enzyme for pneumococcal pyruvate metabolism and pneumococcal survival in blood. Infect Immun 2014; 82:5099-109. [PMID: 25245810 DOI: 10.1128/iai.02005-14] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Streptococcus pneumoniae is a fermentative microorganism and causes serious diseases in humans, including otitis media, bacteremia, meningitis, and pneumonia. However, the mechanisms enabling pneumococcal survival in the host and causing disease in different tissues are incompletely understood. The available evidence indicates a strong link between the central metabolism and pneumococcal virulence. To further our knowledge on pneumococcal virulence, we investigated the role of lactate dehydrogenase (LDH), which converts pyruvate to lactate and is an essential enzyme for redox balance, in the pneumococcal central metabolism and virulence using an isogenic ldh mutant. Loss of LDH led to a dramatic reduction of the growth rate, pinpointing the key role of this enzyme in fermentative metabolism. The pattern of end products was altered, and lactate production was totally blocked. The fermentation profile was confirmed by in vivo nuclear magnetic resonance (NMR) measurements of glucose metabolism in nongrowing cell suspensions of the ldh mutant. In this strain, a bottleneck in the fermentative steps is evident from the accumulation of pyruvate, revealing LDH as the most efficient enzyme in pyruvate conversion. An increase in ethanol production was also observed, indicating that in the absence of LDH the redox balance is maintained through alcohol dehydrogenase activity. We also found that the absence of LDH renders the pneumococci avirulent after intravenous infection and leads to a significant reduction in virulence in a model of pneumonia that develops after intranasal infection, likely due to a decrease in energy generation and virulence gene expression.
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Allan RN, Skipp P, Jefferies J, Clarke SC, Faust SN, Hall-Stoodley L, Webb J. Pronounced metabolic changes in adaptation to biofilm growth by Streptococcus pneumoniae. PLoS One 2014; 9:e107015. [PMID: 25188255 PMCID: PMC4154835 DOI: 10.1371/journal.pone.0107015] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 08/05/2014] [Indexed: 11/19/2022] Open
Abstract
Streptococcus pneumoniae accounts for a significant global burden of morbidity and mortality and biofilm development is increasingly recognised as important for colonization and infection. Analysis of protein expression patterns during biofilm development may therefore provide valuable insights to the understanding of pneumococcal persistence strategies and to improve vaccines. iTRAQ (isobaric tagging for relative and absolute quantification), a high-throughput gel-free proteomic approach which allows high resolution quantitative comparisons of protein profiles between multiple phenotypes, was used to interrogate planktonic and biofilm growth in a clinical serotype 14 strain. Comparative analyses of protein expression between log-phase planktonic and 1-day and 7-day biofilm cultures representing nascent and late phase biofilm growth were carried out. Overall, 244 proteins were identified, of which >80% were differentially expressed during biofilm development. Quantitatively and qualitatively, metabolic regulation appeared to play a central role in the adaptation from the planktonic to biofilm phenotype. Pneumococci adapted to biofilm growth by decreasing enzymes involved in the glycolytic pathway, as well as proteins involved in translation, transcription, and virulence. In contrast, proteins with a role in pyruvate, carbohydrate, and arginine metabolism were significantly increased during biofilm development. Downregulation of glycolytic and translational proteins suggests that pneumococcus adopts a covert phenotype whilst adapting to an adherent lifestyle, while utilization of alternative metabolic pathways highlights the resourcefulness of pneumococcus to facilitate survival in diverse environmental conditions. These metabolic proteins, conserved across both the planktonic and biofilm phenotypes, may also represent target candidates for future vaccine development and treatment strategies. Data are available via ProteomeXchange with identifier PXD001182.
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Affiliation(s)
- Raymond N. Allan
- Academic Unit of Clinical and Experimental Sciences, Faculty of Medicine and Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
- Southampton NIHR Wellcome Trust Clinical Research Facility, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom
- * E-mail:
| | - Paul Skipp
- Centre for Biological Sciences, University of Southampton, Southampton, United Kingdom
- Centre for Proteomic Research, Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Johanna Jefferies
- Academic Unit of Clinical and Experimental Sciences, Faculty of Medicine and Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
- Public Health England, Southampton, United Kingdom
| | - Stuart C. Clarke
- Academic Unit of Clinical and Experimental Sciences, Faculty of Medicine and Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
- Public Health England, Southampton, United Kingdom
- Southampton NIHR Respiratory Biomedical Research Unit, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom
| | - Saul N. Faust
- Academic Unit of Clinical and Experimental Sciences, Faculty of Medicine and Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
- Southampton NIHR Wellcome Trust Clinical Research Facility, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom
- Southampton NIHR Respiratory Biomedical Research Unit, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom
| | - Luanne Hall-Stoodley
- Academic Unit of Clinical and Experimental Sciences, Faculty of Medicine and Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
- Southampton NIHR Wellcome Trust Clinical Research Facility, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom
- Microbial Infection and Immunity, Centre for Microbial Interface Biology, The Ohio State University, Columbus, Ohio, United States of America
| | - Jeremy Webb
- Centre for Biological Sciences, University of Southampton, Southampton, United Kingdom
- Southampton NIHR Respiratory Biomedical Research Unit, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom
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Uptake and metabolism of N-acetylglucosamine and glucosamine by Streptococcus mutans. Appl Environ Microbiol 2014; 80:5053-67. [PMID: 24928869 DOI: 10.1128/aem.00820-14] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glucosamine and N-acetylglucosamine are among the most abundant sugars on the planet, and their introduction into the oral cavity via the diet and host secretions, and through bacterial biosynthesis, provides oral biofilm bacteria with a source of carbon, nitrogen, and energy. In this study, we demonstrated that the dental caries pathogen Streptococcus mutans possesses an inducible system for the metabolism of N-acetylglucosamine and glucosamine. These amino sugars are transported by the phosphoenolpyruvate:sugar phosphotransferase system (PTS), with the glucose/mannose enzyme II permease encoded by manLMN playing a dominant role. Additionally, a previously uncharacterized gene product encoded downstream of the manLMN operon, ManO, was shown to influence the efficiency of uptake and growth on N-acetylglucosamine and, to a lesser extent, glucosamine. A transcriptional regulator, designated NagR, was able to bind the promoter regions in vitro, and repress the expression in vivo, of the nagA and nagB genes, encoding N-acetylglucosamine-6-phosphate deacetylase and glucosamine-6-phosphate deaminase, respectively. The binding activity of NagR could be inhibited by glucosamine-6-phosphate in vitro. Importantly, in contrast to the case with certain other Firmicutes, the gene for de novo synthesis of glucosamine-6-phosphate in S. mutans, glmS, was also shown to be regulated by NagR, and NagR could bind the glmS promoter region in vitro. Finally, metabolism of these amino sugars by S. mutans resulted in the production of significant quantities of ammonia, which can neutralize cytoplasmic pH and increase acid tolerance, thus contributing to enhanced persistence and pathogenic potential.
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36
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Hakansson AP. Pneumococcal Adaptive Responses to Changing Host Environments. J Infect Dis 2014; 210:1-3. [DOI: 10.1093/infdis/jiu084] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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37
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Syk A, Norman M, Fernebro J, Gallotta M, Farmand S, Sandgren A, Normark S, Henriques-Normark B. Emergence of hypervirulent mutants resistant to early clearance during systemic serotype 1 pneumococcal infection in mice and humans. J Infect Dis 2014; 210:4-13. [PMID: 24443543 PMCID: PMC4054898 DOI: 10.1093/infdis/jiu038] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND Streptococcus pneumoniae serotype 1 has a high likelihood of causing invasive disease. Serotype 1 isolates belonging to CC228 are associated with low mortality, while CC217 isolates exhibit high mortality in patients. METHODS Clinical pneumococcal isolates and mutants were evaluated in wild-type C57BL/6 mice, macrophage-depleted mice, neutrophil-depleted mice, and SIGN-R1 knockout mice. In vitro models included binding and phagocytosis by THP-1 cells, capsule measurements, hydrogen peroxide production, and viability assays. RESULTS During early systemic infection in mice with serotype 1, large-colony variants appeared in blood. Similar large colonies were found in blood specimens from patients with invasive disease. Large morphotypes contained higher numbers of viable bacteria, grew faster, produced no or little hydrogen peroxide, and contained mutations in the spxB gene. spxB mutants were considerably more virulent in wild-type mice, less susceptible to early host clearance than wild-type strains after intravenous infection, but impaired in colonization. spxB mutants were less efficiently phagocytosed by macrophages than wild-type bacteria, which, in contrast to spxB mutants, caused more-severe disease when macrophages or SIGN-R1 were depleted. CONCLUSIONS Hypervirulent spxB mutants are selected in both mice and patients and are resistant to early macrophage-mediated clearance.
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Affiliation(s)
- Anna Syk
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet
- Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden
| | - Martin Norman
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet
- Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden
| | - Jenny Fernebro
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet
| | - Marilena Gallotta
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet
| | - Susan Farmand
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet
- Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden
| | - Andreas Sandgren
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet
| | - Staffan Normark
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet
- Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden
| | - Birgitta Henriques-Normark
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet
- Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden
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38
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Overview of community-acquired pneumonia and the role of inflammatory mechanisms in the immunopathogenesis of severe pneumococcal disease. Mediators Inflamm 2013; 2013:490346. [PMID: 24453422 PMCID: PMC3886318 DOI: 10.1155/2013/490346] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Revised: 11/15/2013] [Accepted: 11/17/2013] [Indexed: 12/23/2022] Open
Abstract
Community-acquired pneumonia (CAP) remains a leading cause of morbidity and mortality among the infectious diseases. Despite the implementation of national pneumococcal polyvalent vaccine-based immunisation strategies targeted at high-risk groups, Streptococcus pneumoniae (the pneumococcus) remains the most common cause of CAP. Notwithstanding the HIV pandemic, major challenges confronting the control of CAP include the range of bacterial and viral pathogens causing this condition, the ever-increasing problem of antibiotic resistance worldwide, and increased vulnerability associated with steadily aging populations in developed countries. These and other risk factors, as well as diagnostic strategies, are covered in the first section of this review. Thereafter, the review is focused on the pneumococcus, specifically the major virulence factors of this microbial pathogen and their role in triggering overexuberant inflammatory responses which contribute to the immunopathogenesis of invasive disease. The final section of the review is devoted to a consideration of pharmacological, anti-inflammatory strategies with adjunctive potential in the antimicrobial chemotherapy of CAP. This is focused on macrolides, corticosteroids, and statins with respect to their modes of anti-inflammatory action, current status, and limitations.
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