1
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Bier SB, Toska J, Zhao W, Suthianthong P, Proespraiwong P, Robins WP, Mekalanos J. A coordinated attack by a bacterial secretion system and a small molecule drives prey specificity. Commun Biol 2024; 7:958. [PMID: 39117895 PMCID: PMC11310501 DOI: 10.1038/s42003-024-06637-0] [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: 02/15/2024] [Accepted: 07/26/2024] [Indexed: 08/10/2024] Open
Abstract
Vibrio species are recognized for their role in food- and water-borne diseases in humans, fish, and aquatic invertebrates. We screened bacterial strains isolated from raw food shrimp for those that are bactericidal to Vibrio strains. Here we identify and characterize Aeromonas dhakensis strain A603 which shows robust bactericidal activity specifically towards Vibrio and related taxa but less potency toward other Gram-negative species. Using the A603 genome and genetic analysis, we show that two antibacterial mechanisms account for its vibriocidal activity -- a highly potent Type Six Secretion System (T6SS) and biosynthesis of a vibriocidal phenazine-like small molecule, named here as Ad-Phen. Further analysis indicates coregulation between Ad-Phen and a pore-forming T6SS effector TseC, which potentiates V. cholerae to killing by Ad-Phen.
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Affiliation(s)
- S B Bier
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - J Toska
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - W Zhao
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Guangdong Provincial Key Laboratory of Colorectal and Pelvic Floor Disease. The Sixth Affiliated Hospital, School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - P Suthianthong
- Charoen Pokphand Foods PCL. Aquatic Animal Health Research Center, Samutsakorn, Thailand
| | - P Proespraiwong
- Department of Biochemistry, Faculty of Science, Kasetsart University, Bangkok, Thailand
| | - W P Robins
- Department of Microbiology, Harvard Medical School, Boston, MA, USA.
| | - J Mekalanos
- Department of Microbiology, Harvard Medical School, Boston, MA, USA.
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2
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Virgo M, Mostowy S, Ho BT. Use of zebrafish to identify host responses specific to type VI secretion system mediated interbacterial antagonism. PLoS Pathog 2024; 20:e1012384. [PMID: 39024393 PMCID: PMC11288455 DOI: 10.1371/journal.ppat.1012384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 07/30/2024] [Accepted: 07/01/2024] [Indexed: 07/20/2024] Open
Abstract
Interbacterial competition is known to shape the microbial communities found in the host, however the interplay between this competition and host defense are less clear. Here, we use the zebrafish hindbrain ventricle (HBV) as an in vivo platform to investigate host responses to defined bacterial communities with distinct forms of interbacterial competition. We found that antibacterial activity of the type VI secretion system (T6SS) from both Vibrio cholerae and Acinetobacter baylyi can induce host inflammation and sensitize the host to infection independent of any individual effector. Chemical suppression of inflammation could resolve T6SS-dependent differences in host survival, but the mechanism by which this occurred differed between the two bacterial species. By contrast, colicin-mediated antagonism elicited by an avirulent strain of Shigella sonnei induced a negligible host response despite being a more potent bacterial killer, resulting in no impact on A. baylyi or V. cholerae virulence. Altogether, these results provide insight into how different modes of interbacterial competition in vivo affect the host in distinct ways.
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Affiliation(s)
- Mollie Virgo
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, London, United Kingdom
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, Keppel Street, London, United Kingdom
| | - Serge Mostowy
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, Keppel Street, London, United Kingdom
| | - Brian T. Ho
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, London, United Kingdom
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom
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3
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Casiano González A, Pacheco Villanueva A, Castro-Alarcón N, Méndez J, Oropeza R, Martínez-Santos VI. A novel chaperone-effector-immunity system identified in uropathogenic Escherichia coli UMN026. PeerJ 2024; 12:e17336. [PMID: 38784397 PMCID: PMC11114119 DOI: 10.7717/peerj.17336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 04/15/2024] [Indexed: 05/25/2024] Open
Abstract
Background Urinary tract infections (UTIs) are very common worldwide. According to their symptomatology, these infections are classified as pyelonephritis, cystitis, or asymptomatic bacteriuria (AB). Approximately 75-95% of UTIs are caused by uropathogenic Escherichia coli (UPEC), which is an extraintestinal bacterium that possesses virulence factors for bacterial adherence and invasion in the urinary tract. In addition, UPEC possesses type 6 secretion systems (T6SS) as virulence mechanisms that can participate in bacterial competition and in bacterial pathogenicity. UPEC UMN026 carries three genes, namely, ECUMN_0231, ECUMN_0232, and ECUMN_0233, which encode three uncharacterized proteins related to the T6SS that are conserved in strains from phylogroups B2 and D and have been proposed as biomarkers of UTIs. Aim To analyze the frequency of the ECUMN_0231, ECUMN_0232, ECUMN_0233, and vgrG genes in UTI isolates, as well as their expression in Luria Bertani (LB) medium and urine; to determine whether these genes are related to UTI symptoms or bacterial competence and to identify functional domains on the putative proteins. Methods The frequency of the ECUMN and vgrG genes in 99 clinical isolates from UPEC was determined by endpoint PCR. The relationship between gene presence and UTI symptomatology was determined using the chi2 test, with p < 0.05 considered to indicate statistical significance. The expression of the three ECUMN genes and vgrG was analyzed by RT-PCR. The antibacterial activity of strain UMN026 was determined by bacterial competence assays. The identification of functional domains and the docking were performed using bioinformatic tools. Results The ECUMN genes are conserved in 33.3% of clinical isolates from patients with symptomatic and asymptomatic UTIs and have no relationship with UTI symptomatology. Of the ECUMN+ isolates, only five (15.15%, 5/33) had the three ECUMN and vgrG genes. These genes were expressed in LB broth and urine in UPEC UMN026 but not in all the clinical isolates. Strain UMN026 had antibacterial activity against UPEC clinical isolate 4014 (ECUMN-) and E. faecalis but not against isolate 4012 (ECUMN+). Bioinformatics analysis suggested that the ECUMN genes encode a chaperone/effector/immunity system. Conclusions The ECUMN genes are conserved in clinical isolates from symptomatic and asymptomatic patients and are not related to UTI symptoms. However, these genes encode a putative chaperone/effector/immunity system that seems to be involved in the antibacterial activity of strain UMN026.
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Affiliation(s)
- América Casiano González
- Microbiology Research Laboratory, Faculty of Chemical Biological Sciences, Universidad Autónoma de Guerrero, Chilpancingo, Guerrero, Mexico
| | - Arantxa Pacheco Villanueva
- Microbiology Research Laboratory, Faculty of Chemical Biological Sciences, Universidad Autónoma de Guerrero, Chilpancingo, Guerrero, Mexico
| | - Natividad Castro-Alarcón
- Microbiology Research Laboratory, Faculty of Chemical Biological Sciences, Universidad Autónoma de Guerrero, Chilpancingo, Guerrero, Mexico
| | - Julio Méndez
- Department of Molecular Microbiology, Institute of Biotechnology, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
| | - Ricardo Oropeza
- Department of Molecular Microbiology, Institute of Biotechnology, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
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Carobbi A, Leo K, Di Nepi S, Bosis E, Salomon D, Sessa G. PIX is an N-terminal delivery domain that defines a class of polymorphic T6SS effectors in Enterobacterales. Cell Rep 2024; 43:114015. [PMID: 38568810 DOI: 10.1016/j.celrep.2024.114015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 02/13/2024] [Accepted: 03/14/2024] [Indexed: 04/05/2024] Open
Abstract
The type VI secretion system (T6SS), a widespread protein delivery apparatus, plays a role in bacterial competition by delivering toxic effectors into neighboring cells. Identifying new T6SS effectors and deciphering the mechanism that governs their secretion remain major challenges. Here, we report two orphan antibacterial T6SS effectors in the pathogen Pantoea agglomerans (Pa). These effectors share an N-terminal domain, Pantoea type six (PIX), that defines a widespread class of polymorphic T6SS effectors in Enterobacterales. We show that the PIX domain is necessary and sufficient for T6SS-mediated effector secretion and that PIX binds to a specialized Pa VgrG protein outside its C-terminal toxic domain. Our findings underline the importance of identifying and characterizing delivery domains in polymorphic toxin classes as a tool to reveal effectors and shed light on effector delivery mechanisms.
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Affiliation(s)
- Andrea Carobbi
- Department of Clinical Microbiology and Immunology, School of Medicine, Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv, Israel; School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ksenia Leo
- Department of Clinical Microbiology and Immunology, School of Medicine, Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv, Israel; School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Simone Di Nepi
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Eran Bosis
- Department of Biotechnology Engineering, Braude College of Engineering, Karmiel, Israel
| | - Dor Salomon
- Department of Clinical Microbiology and Immunology, School of Medicine, Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv, Israel.
| | - Guido Sessa
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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Grant NA, Donkor GY, Sontz JT, Soto W, Waters CM. Deployment of a Vibrio cholerae ordered transposon mutant library in a quorum-competent genetic background. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.10.31.564941. [PMID: 37961142 PMCID: PMC10634969 DOI: 10.1101/2023.10.31.564941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Vibrio cholerae, the causative agent of cholera, has sparked seven pandemics in recent centuries, with the current one being the most prolonged. V. cholerae's pathogenesis hinges on its ability to switch between low and high cell density gene regulatory states, enabling transmission between host and the environment. Previously, a transposon mutant library for V. cholerae was created to support investigations aimed toward uncovering the genetic determinants of its pathogenesis. However, subsequent sequencing uncovered a mutation in the gene luxO of the parent strain, rendering mutants unable to exhibit high cell density behaviors. In this study, we used chitin-independent natural transformation to move transposon insertions from these low cell density mutants into a wildtype genomic background. Library transfer was aided by a novel gDNA extraction we developed using thymol, which also showed high lysis-specificity for Vibrio. The resulting Grant Library comprises 3,102 unique transposon mutants, covering 79.8% of V. cholerae's open reading frames. Whole genome sequencing of randomly selected mutants demonstrates 100% precision in transposon transfer to cognate genomic positions of the recipient strain. Notably, in no instance did the luxO mutation transfer into the wildtype background. Our research uncovered density-dependent epistasis in growth on inosine, an immunomodulatory metabolite secreted by gut bacteria that is implicated in enhancing gut barrier functions. Additionally, Grant Library mutants retain the plasmid that enables rapid, scarless genomic editing. In summary, the Grant Library reintroduces organismal relevant genetic contexts absent in the low cell density locked library equivalent.
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Affiliation(s)
- Nkrumah A. Grant
- Department of Microbiology, University of Illinois Urbana-Champaign, Urbana, IL
- Department of Microbiology, Genetics, and Immunology, Michigan State University, East Lansing MI
- BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI
| | | | - Jordan T. Sontz
- MSU College of Osteopathic Medicine, Michigan State University, East Lansing, MI
| | - William Soto
- Department of Biology, College of William and Mary, Williamsburg, VA
| | - Christopher M. Waters
- Department of Microbiology, Genetics, and Immunology, Michigan State University, East Lansing MI
- BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI
- MSU College of Osteopathic Medicine, Michigan State University, East Lansing, MI
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6
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Alvarado Obando M, Rey-Varela D, Cava F, Dörr T. Genetic interaction mapping reveals functional relationships between peptidoglycan endopeptidases and carboxypeptidases. PLoS Genet 2024; 20:e1011234. [PMID: 38598601 PMCID: PMC11034669 DOI: 10.1371/journal.pgen.1011234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 04/22/2024] [Accepted: 03/25/2024] [Indexed: 04/12/2024] Open
Abstract
Peptidoglycan (PG) is the main component of the bacterial cell wall; it maintains cell shape while protecting the cell from internal osmotic pressure and external environmental challenges. PG synthesis is essential for bacterial growth and survival, and a series of PG modifications are required to allow expansion of the sacculus. Endopeptidases (EPs), for example, cleave the crosslinks between adjacent PG strands to allow the incorporation of newly synthesized PG. EPs are collectively essential for bacterial growth and must likely be carefully regulated to prevent sacculus degradation and cell death. However, EP regulation mechanisms are poorly understood. Here, we used TnSeq to uncover novel EP regulators in Vibrio cholerae. This screen revealed that the carboxypeptidase DacA1 (PBP5) alleviates EP toxicity. dacA1 is essential for viability on LB medium, and this essentiality was suppressed by EP overexpression, revealing that EP toxicity both mitigates, and is mitigated by, a defect in dacA1. A subsequent suppressor screen to restore viability of ΔdacA1 in LB medium identified hypomorphic mutants in the PG synthesis pathway, as well as mutations that promote EP activation. Our data thus reveal a more complex role of DacA1 in maintaining PG homeostasis than previously assumed.
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Affiliation(s)
- Manuela Alvarado Obando
- Department of Microbiology, Cornell University, Ithaca, New York, United States of America
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, United States of America
| | - Diego Rey-Varela
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Center for Microbial Research (UCMR), Science for Life Laboratory (SciLifeLab), Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Felipe Cava
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Center for Microbial Research (UCMR), Science for Life Laboratory (SciLifeLab), Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Tobias Dörr
- Department of Microbiology, Cornell University, Ithaca, New York, United States of America
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, United States of America
- Cornell Institute for Host-Microbe Interactions and Disease (CIHMID), Ithaca, New York, United States of America
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Ramamoorthy S, Pena M, Ghosh P, Liao YY, Paret M, Jones JB, Potnis N. Transcriptome profiling of type VI secretion system core gene tssM mutant of Xanthomonas perforans highlights regulators controlling diverse functions ranging from virulence to metabolism. Microbiol Spectr 2024; 12:e0285223. [PMID: 38018859 PMCID: PMC10782981 DOI: 10.1128/spectrum.02852-23] [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: 07/14/2023] [Accepted: 10/20/2023] [Indexed: 11/30/2023] Open
Abstract
IMPORTANCE T6SS has received attention due to its significance in mediating interorganismal competition through contact-dependent release of effector molecules into prokaryotic and eukaryotic cells. Reverse-genetic studies have indicated the role of T6SS in virulence in a variety of plant pathogenic bacteria, including the one studied here, Xanthomonas. However, it is not clear whether such effect on virulence is merely due to a shift in the microbiome-mediated protection or if T6SS is involved in a complex virulence regulatory network. In this study, we conducted in vitro transcriptome profiling in minimal medium to decipher the signaling pathways regulated by tssM-i3* in X. perforans AL65. We show that TssM-i3* regulates the expression of a suite of genes associated with virulence and metabolism either directly or indirectly by altering the transcription of several regulators. These findings further expand our knowledge on the intricate molecular circuits regulated by T6SS in phytopathogenic bacteria.
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Affiliation(s)
- Sivakumar Ramamoorthy
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA
| | - Michelle Pena
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA
| | - Palash Ghosh
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA
| | - Ying-Yu Liao
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
| | - Mathews Paret
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
| | - Jeffrey B. Jones
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
| | - Neha Potnis
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA
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Garin T, Brin C, Préveaux A, Brault A, Briand M, Simonin M, Barret M, Journet L, Sarniguet A. The type VI secretion system of Stenotrophomonas rhizophila CFBP13503 limits the transmission of Xanthomonas campestris pv. campestris 8004 from radish seeds to seedlings. MOLECULAR PLANT PATHOLOGY 2024; 25:e13412. [PMID: 38279854 PMCID: PMC10777753 DOI: 10.1111/mpp.13412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 10/20/2023] [Accepted: 11/27/2023] [Indexed: 01/29/2024]
Abstract
Stenotrophomonas rhizophila CFBP13503 is a seedborne commensal bacterial strain, which is efficiently transmitted to seedlings and can outcompete the phytopathogenic bacterium Xanthomonas campestris pv. campestris (Xcc8004). The type VI secretion system (T6SS), an interference contact-dependent mechanism, is a critical component of interbacterial competition. The involvement of the T6SS of S. rhizophila CFBP13503 in the inhibition of Xcc8004 growth and seed-to-seedling transmission was assessed. The T6SS cluster of S. rhizophila CFBP13503 and nine putative effectors were identified. Deletion of two T6SS structural genes, hcp and tssB, abolished the competitive advantage of S. rhizophila against Xcc8004 in vitro. The population sizes of these two bacterial species were monitored in seedlings after inoculation of radish seeds with mixtures of Xcc8004 and either S. rhizophila wild-type (wt) strain or isogenic hcp mutant. A significant decrease in the population size of Xcc8004 was observed during confrontation with the S. rhizophila wt in comparison with T6SS-deletion mutants in germinated seeds and seedlings. We found that the T6SS distribution among 835 genomes of the Stenotrophomonas genus is scarce. In contrast, in all available S. rhizophila genomes, T6SS clusters are widespread and mainly belong to the T6SS group i4. In conclusion, the T6SS of S. rhizophila CFBP13503 is involved in the antibiosis against Xcc8004 and reduces seedling transmission of Xcc8004 in radish. The distribution of this T6SS cluster in the S. rhizophila complex could make it possible to exploit these strains as biocontrol agents against X. campestris pv. campestris.
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Affiliation(s)
- Tiffany Garin
- Univ Angers, Institut Agro, INRAE, IRHS, SFR QUASAVAngersFrance
| | - Chrystelle Brin
- Univ Angers, Institut Agro, INRAE, IRHS, SFR QUASAVAngersFrance
| | - Anne Préveaux
- Univ Angers, Institut Agro, INRAE, IRHS, SFR QUASAVAngersFrance
| | - Agathe Brault
- Univ Angers, Institut Agro, INRAE, IRHS, SFR QUASAVAngersFrance
| | - Martial Briand
- Univ Angers, Institut Agro, INRAE, IRHS, SFR QUASAVAngersFrance
| | - Marie Simonin
- Univ Angers, Institut Agro, INRAE, IRHS, SFR QUASAVAngersFrance
| | - Matthieu Barret
- Univ Angers, Institut Agro, INRAE, IRHS, SFR QUASAVAngersFrance
| | - Laure Journet
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie, Bioénergies et Biotechnologie, Institut de Microbiologie de la MéditerranéeAix‐Marseille Université‐CNRS, UMR 7255MarseilleFrance
| | - Alain Sarniguet
- Univ Angers, Institut Agro, INRAE, IRHS, SFR QUASAVAngersFrance
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MacGillivray KA, Ng SL, Wiesenfeld S, Guest RL, Jubery T, Silhavy TJ, Ratcliff WC, Hammer BK. Trade-offs constrain adaptive pathways to the type VI secretion system survival. iScience 2023; 26:108332. [PMID: 38025790 PMCID: PMC10679819 DOI: 10.1016/j.isci.2023.108332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 08/25/2023] [Accepted: 10/22/2023] [Indexed: 12/01/2023] Open
Abstract
The Type VI Secretion System (T6SS) is a nano-harpoon used by many bacteria to inject toxins into neighboring cells. While much is understood about mechanisms of T6SS-mediated toxicity, less is known about the ways that competitors can defend themselves against this attack, especially in the absence of their own T6SS. Here we subjected eight replicate populations of Escherichia coli to T6SS attack by Vibrio cholerae. Over ∼500 generations of competition, isolates of the E. coli populations evolved to survive T6SS attack an average of 27-fold better, through two convergently evolved pathways: apaH was mutated in six of the eight replicate populations, while the other two populations each had mutations in both yejM and yjeP. However, the mutations we identified are pleiotropic, reducing cellular growth rates, and increasing susceptibility to antibiotics and elevated pH. These trade-offs help us understand how the T6SS shapes the evolution of bacterial interactions.
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Affiliation(s)
- Kathryn A. MacGillivray
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
| | - Siu Lung Ng
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
| | - Sophia Wiesenfeld
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
| | - Randi L. Guest
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Tahrima Jubery
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
| | - Thomas J. Silhavy
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - William C. Ratcliff
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
| | - Brian K. Hammer
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
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10
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Mathieu-Denoncourt A, Duperthuy M. The VxrAB two-component system is important for the polymyxin B-dependent activation of the type VI secretion system in Vibrio cholerae O1 strain A1552. Can J Microbiol 2023; 69:393-406. [PMID: 37343290 DOI: 10.1139/cjm-2023-0026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/23/2023]
Abstract
The type VI secretion system (T6SS) is used by bacteria for virulence, resistance to grazing, and competition with other bacteria. We previously demonstrated that the role of the T6SS in interbacterial competition and in resistance to grazing is enhanced in Vibrio cholerae in the presence of subinhibitory concentrations of polymyxin B. Here, we performed a global quantitative proteomic analysis and a targeted transcriptomic analysis of the T6SS-known regulators in V. cholerae grown with and without polymyxin B. The proteome of V. cholerae is greatly modified by polymyxin B with more than 39% of the identified cellular proteins displaying a difference in their abundance, including T6SS-related proteins. We identified a regulator whose abundance and expression are increased in the presence of polymyxin B, vxrB, the response regulator of the two-component system VxrAB (VCA0565-66). In vxrAB, vxrA and vxrB deficient mutants, the expression of both hcp copies (VC1415 and VCA0017), although globally reduced, was not modified by polymyxin B. These hcp genes encode an identical protein Hcp, which is the major component of the T6SS syringe. Thus, the upregulation of the T6SS in the presence of polymyxin B appears to be, at least in part, due to the two-component system VxrAB.
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Affiliation(s)
- Annabelle Mathieu-Denoncourt
- Département de Microbiologie, infectiologie et immunologie, Faculté de médecine, Université de Montréal, Montréal, QC, Canada
| | - Marylise Duperthuy
- Département de Microbiologie, infectiologie et immunologie, Faculté de médecine, Université de Montréal, Montréal, QC, Canada
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11
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Obando MA, Dörr T. Novel role for peptidoglycan carboxypeptidases in maintaining the balance between bacterial cell wall synthesis and degradation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.12.548665. [PMID: 37503280 PMCID: PMC10369974 DOI: 10.1101/2023.07.12.548665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Peptidoglycan (PG) is the main component of the bacterial cell wall; it maintains cell shape while protecting the cell from internal osmotic pressure and external environmental challenges. PG synthesis is essential for bacterial growth and survival, and a series of PG modifications are required to allow expansion of the sacculus. Endopeptidases (EPs), for example, cleave the crosslinks between adjacent PG strands to allow the incorporation of newly synthesized PG. EPs are collectively essential for bacterial growth and must likely be carefully regulated to prevent sacculus degradation and cell death. However, EP regulation mechanisms are poorly understood. Here, we used TnSeq to uncover novel EP regulation factors in Vibrio cholerae. This screen revealed that the carboxypeptidase DacA1 (PBP5) alleviates EP toxicity. dacA1 is essential for viability on LB medium, and this essentiality was suppressed by EP overexpression, revealing that EP toxicity both mitigates, and is mitigated by, a defect in dacA1. A subsequent suppressor screen to restore viability of ΔdacA1 in LB medium was answered by hypomorphic mutants in the PG synthesis pathway, as well as mutations that promote PG degradation. Our data thus reveal a key role of DacA1 in maintaining the balance between PG synthesis and degradation.
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Affiliation(s)
- Manuela Alvarado Obando
- Department of Microbiology, Cornell University, Ithaca, NY
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY
| | - Tobias Dörr
- Department of Microbiology, Cornell University, Ithaca, NY
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY
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12
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Allsopp LP, Bernal P. Killing in the name of: T6SS structure and effector diversity. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001367. [PMID: 37490402 PMCID: PMC10433429 DOI: 10.1099/mic.0.001367] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 07/12/2023] [Indexed: 07/27/2023]
Abstract
The life of bacteria is challenging, to endure bacteria employ a range of mechanisms to optimize their environment, including deploying the type VI secretion system (T6SS). Acting as a bacterial crossbow, this system delivers effectors responsible for subverting host cells, killing competitors and facilitating general secretion to access common goods. Due to its importance, this lethal machine has been evolutionarily maintained, disseminated and specialized to fulfil these vital functions. In fact, T6SS structural clusters are present in over 25 % of Gram-negative bacteria, varying in number from one to six different genetic clusters per organism. Since its discovery in 2006, research on the T6SS has rapidly progressed, yielding remarkable breakthroughs. The identification and characterization of novel components of the T6SS, combined with biochemical and structural studies, have revealed fascinating mechanisms governing its assembly, loading, firing and disassembly processes. Recent findings have also demonstrated the efficacy of this system against fungal and Gram-positive cells, expanding its scope. Ongoing research continues to uncover an extensive and expanding repertoire of T6SS effectors, the genuine mediators of T6SS function. These studies are shedding light on new aspects of the biology of prokaryotic and eukaryotic organisms. This review provides a comprehensive overview of the T6SS, highlighting recent discoveries of its structure and the diversity of its effectors. Additionally, it injects a personal perspective on avenues for future research, aiming to deepen our understanding of this combative system.
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Affiliation(s)
- Luke P. Allsopp
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Patricia Bernal
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla 41012, Spain
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13
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Keller M, Han X, Dörr T. Disrupting Central Carbon Metabolism Increases β-Lactam Antibiotic Susceptibility in Vibrio cholerae. J Bacteriol 2023; 205:e0047622. [PMID: 36840595 PMCID: PMC10029711 DOI: 10.1128/jb.00476-22] [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: 12/21/2022] [Accepted: 01/31/2023] [Indexed: 02/24/2023] Open
Abstract
Antibiotic tolerance, the ability of bacteria to sustain viability in the presence of typically bactericidal antibiotics for extended time periods, is an understudied contributor to treatment failure. The Gram-negative pathogen Vibrio cholerae, the causative agent of cholera, becomes highly tolerant to β-lactam antibiotics (penicillin and related compounds) in a process requiring the two-component system VxrAB. VxrAB is induced by exposure to cell wall damaging conditions, which results in the differential regulation of >100 genes. While the effectors of VxrAB are relatively well known, VxrAB environment-sensing and activation mechanisms remain a mystery. Here, we used transposon mutagenesis to screen for mutants that spontaneously upregulate VxrAB signaling. This screen was answered by genes known to be required for proper cell envelope homeostasis, validating the approach. Unexpectedly, we also uncovered a new connection between central carbon metabolism and antibiotic tolerance in Vibrio cholerae. Inactivation of pgi (vc0374, coding for glucose-6-phosphate isomerase) resulted in an intracellular accumulation of glucose-6-phosphate and fructose-6-phosphate, concomitant with a marked cell envelope defect, resulting in VxrAB induction. Deletion of pgi also increased sensitivity to β-lactams and conferred a growth defect on salt-free LB, phenotypes that could be suppressed by deleting sugar uptake systems and by supplementing cell wall precursors in the growth medium. Our data suggest an important connection between central metabolism and cell envelope integrity and highlight a potential new target for developing novel antimicrobial agents. IMPORTANCE Antibiotic tolerance (the ability to survive exposure to antibiotics) is a stepping stone toward antibiotic resistance (the ability to grow in the presence of antibiotics), an increasingly common cause of antibiotic treatment failure. The mechanisms promoting tolerance are poorly understood. Here, we identified central carbon metabolism as a key contributor to antibiotic tolerance and resistance. A strain with a mutation in a sugar utilization pathway accumulates metabolites that likely shut down the synthesis of cell wall precursors, which weakens the cell wall and thus increases susceptibility to cell wall-active drugs. Our results illuminate the connection between central carbon metabolism and cell wall homeostasis in V. cholerae and suggest that interfering with metabolism may be a fruitful future strategy for the development of antibiotic adjuvants.
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Affiliation(s)
- Megan Keller
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, USA
| | - Xiang Han
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, USA
| | - Tobias Dörr
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, USA
- Department of Microbiology, Cornell University, Ithaca, New York, USA
- Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, New York, USA
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14
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Pérez-Lorente AI, Molina-Santiago C, de Vicente A, Romero D. Sporulation Activated via σ W Protects Bacillus from a Tse1 Peptidoglycan Hydrolase Type VI Secretion System Effector. Microbiol Spectr 2023; 11:e0504522. [PMID: 36916921 PMCID: PMC10100999 DOI: 10.1128/spectrum.05045-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 02/21/2023] [Indexed: 03/16/2023] Open
Abstract
Within bacterial communities, community members engage in interactions employing diverse offensive and defensive tools to reach coexistence. Extracellular-matrix production and sporulation are defensive mechanisms used by Bacillus subtilis cells when they interact with Pseudomonas chlororaphis strains expressing a type VI secretion system (T6SS). Here, we define Tse1 as the main toxin mobilized by the Pseudomonas chlororaphis T6SS that triggers sporulation in Bacillus subtilis. We characterize Tse1 as a peptidoglycan hydrolase that indirectly alters the dynamics and functionality of the Bacillus cell membrane. We also delineate the response of Bacillus cells to Tse1, which through the coordinated actions of the extracellular sigma factor σW and the cytoplasmic histidine kinases KinA and KinB, culminates in activation of the sporulation cascade. We propose that this cellular developmental response permits bacilli to defend against the toxicity of T6SS-mobilized Tse1 effector. IMPORTANCE The study of bacterial interactions is helping to define species-specific strategies used to modulate the competition dynamics underlying the development of community compositions. In this study, we deciphered the role of Pseudomonas T6SS when competing with Bacillus and the mechanism by which a T6SS-toxin modifies Bacillus physiology. We found that Pseudomonas triggers Bacillus sporulation by injecting through T6SS a toxin that we called Tse1. We found that Tse1 is a hydrolase that degrades Bacillus peptidoglycan and indirectly damages Bacillus membrane functionality. In addition, we demonstrated the mechanism by which Bacillus cells increase the sporulation rate upon recognition of the presence of Tse1. Interestingly, asporogenic Bacillus cells are more sensitive to T6SS activity, which led us to propose sporulation as a last resort of bacilli to overcome this family of toxins.
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Affiliation(s)
- Alicia I. Pérez-Lorente
- Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Departamento de Microbiología, Universidad de Málaga, Málaga, Spain
| | - Carlos Molina-Santiago
- Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Departamento de Microbiología, Universidad de Málaga, Málaga, Spain
| | - Antonio de Vicente
- Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Departamento de Microbiología, Universidad de Málaga, Málaga, Spain
| | - Diego Romero
- Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Departamento de Microbiología, Universidad de Málaga, Málaga, Spain
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15
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Type VI Secretion Systems: Environmental and Intra-host Competition of Vibrio cholerae. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1404:41-63. [PMID: 36792870 DOI: 10.1007/978-3-031-22997-8_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
The Vibrio Type VI Secretion System (T6SS) is a harpoon-like nanomachine that serves as a defense system and is encoded by approximately 25% of all gram-negative bacteria. In this chapter, we describe the structure of the T6SS in different Vibrio species and outline how the use of different T6SS effector and immunity proteins control kin selection. We summarize the genetic loci that encode the structural elements that make up the Vibrio T6SSs and how these gene clusters are regulated. Finally, we provide insights into T6SS-based competitive dynamics, the role of T6SS genetic exchange in those competitive dynamics, and roles for the Vibrio T6SS in virulence.
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16
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Liu M, Zhao MY, Wang H, Wang ZH, Wang Z, Liu Y, Li YP, Dong T, Fu Y. Pesticin-Like Effector VgrG3 cp Targeting Peptidoglycan Delivered by the Type VI Secretion System Contributes to Vibrio cholerae Interbacterial Competition. Microbiol Spectr 2023; 11:e0426722. [PMID: 36625646 PMCID: PMC9927483 DOI: 10.1128/spectrum.04267-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Accepted: 12/13/2022] [Indexed: 01/11/2023] Open
Abstract
Vibrio cholerae can utilize a type VI secretion system (T6SS) to increase its intra- and interspecies competition. However, much still remains to be understood about the underlying mechanism of this intraspecies competition. In this study, we isolated an environmental V. cholerae strain E1 that lacked the typical virulence factors toxin-coregulated pilus and cholera toxin and that encoded a functional T6SS. We identified an evolved VgrG3 variant with a predicted C-terminal pesticin-like domain in V. cholerae E1, designated VgrG3cp. Using heterologous expression, protein secretion, and peptidoglycan-degrading assays, we demonstrated that VgrG3cp is a T6SS-dependent effector harboring cell wall muramidase activity and that its toxicity can be neutralized by cognate immunity protein TsiV3cp. Site-directed mutagenesis proved that the aspartic acid residue at position 867 is crucial for VgrG3cp-mediated antibacterial activity. Bioinformatic analysis showed that genes encoding VgrG3cp-like homologs are distributed in Vibrio species, are linked with T6SS structural genes and auxiliary genes, and the vgrG3cp-tsiV3cp gene pair of V. cholerae probably evolved from Vibrio anguillarum and Vibrio fluvialis via homologous recombination. Through a time-lapse microscopy assay, we directly determined that cells accumulating VgrG3cp disrupted bacterial division, while the cells continued to increase in size until the loss of membrane potential and cell wall breakage and finally burst. The results of the competitive killing assay showed that VgrG3cp contributes to V. cholerae interspecies competition. Collectively, our study revealed a novel T6SS E-I pair representing a new T6SS toxin family which allows V. cholerae to gain dominance within polymicrobial communities by T6SS. IMPORTANCE The type VI secretion system used by a broad range of Gram-negative bacteria delivers toxic proteins to target adjacent eukaryotic and prokaryotic cells. Diversification of effector proteins determines the complex bacterium-bacterium interactions and impacts the health of hosts and environmental ecosystems in which bacteria reside. This work uncovered an evolved valine-glycine repeat protein G3, carrying a C-terminal pesticin-like domain (VgrG3cp), which has been suggested to harbor cell wall hydrolase activity and is able to affect cell division and the integrity of cell wall structure. Pesticin-like homologs constitute a family of T6SS-associated effectors targeting bacterial peptidoglycan which are distributed in Vibrio species, and genetic loci of them are linked with T6SS structural genes and auxiliary genes. T6SS-delivered VgrG3cp mediated broad-spectrum antibacterial activity for several microorganisms tested, indicating that VgrG3cp-mediated antimicrobial activity is capable of conferring bacteria a competitive advantage over competitors in the same niches.
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Affiliation(s)
- Ming Liu
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Meng-Yu Zhao
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
- The First Affiliated Hospital, Southern University of Science and Technology, Shenzhen, China
| | - Heng Wang
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Zeng-Hang Wang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Zhao Wang
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Ying Liu
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Yin-Peng Li
- The First Affiliated Hospital, Southern University of Science and Technology, Shenzhen, China
| | - Tao Dong
- Department of Immunology and Microbiology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Yang Fu
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
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17
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Santoriello FJ, Kirchberger PC, Boucher Y, Pukatzki S. Pandemic Vibrio cholerae acquired competitive traits from an environmental Vibrio species. Life Sci Alliance 2023; 6:6/2/e202201437. [PMID: 36446527 PMCID: PMC9711863 DOI: 10.26508/lsa.202201437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 11/05/2022] [Accepted: 11/07/2022] [Indexed: 11/30/2022] Open
Abstract
Vibrio cholerae is a human pathogen that thrives in estuarine environments. Within the environment and human host, V. cholerae uses the type VI secretion system (T6SS) to inject toxic effectors into neighboring microbes and to establish its replicative niche. V. cholerae strains encode a wide variety of horizontally shared effectors, but pandemic isolates encode an identical set of distinct effectors. Effector set retention in pandemic strains despite mobility between disparate strains suggests that horizontal acquisition of these effectors was crucial for evolving pandemic V. cholerae We attempted to locate the donor of the pandemic effectors to V. cholerae To this end, we identified potential gene transfer events of the pandemic-associated T6SS clusters between a fish pathogen, Vibrio anguillarum, and V. cholerae We supported the likelihood of interaction between these species by demonstrating that homologous effector-immunity pairs from V. cholerae and V. anguillarum can cross-neutralize one another. Thus, V. anguillarum constitutes an environmental reservoir of pandemic-associated V. cholerae T6SS effectors that may have initially facilitated competition between pre-pandemic V. cholerae and V. anguillarum for an environmental niche.
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Affiliation(s)
- Francis J Santoriello
- Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.,Department of Biology, The City College of New York, New York, NY, USA
| | - Paul C Kirchberger
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Yann Boucher
- Saw Swee Hock School of Public Health and National University Hospital System, National University of Singapore, Singapore, Singapore.,Singapore Centre for Environmental Life Sciences Engineering, National University of Singapore, Singapore, Singapore.,Infectious Diseases Translational Research Program, Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore and National University Hospital System, Singapore, Singapore
| | - Stefan Pukatzki
- Department of Biology, The City College of New York, New York, NY, USA
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18
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Zadnova SP, Plekhanov NA, Spirina AY, Kritskiy AA. Comparative analysis of the structure and expression of the <i>vasH</i> regulatory gene of type VI secretion system in toxigenic and non-toxigenic <i>Vibrio cholerae</i> strains. JOURNAL OF MICROBIOLOGY, EPIDEMIOLOGY AND IMMUNOBIOLOGY 2023. [DOI: 10.36233/0372-9311-255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Objective. The comparative analysis of the structure of the regulatory gene vasH of the type VI secretion system and its expression in toxigenic and non-toxigenic V. cholerae O1, biovar El Tor strains.
Materials and methods. We used 35 strains isolated from patients and from the environmental samples in the territory of Russia and Ukraine between 1970 and 2017. Analysis of the structure of the vasH gene and the amino acid sequence of the protein was carried out using Ugene 1.32, Mega X, and Bioedit v. 7.0.9.0. The relative level of vasH expression was studied by 2Ct.
Results. The The structure of the vasH gene and the amino acid sequence of VasH protein in toxigenic typical strains and genovariants of V. cholerae O1, El Tor biovar (genotype ctxA+tcpA+) have been shown to be identical to the reference V. cholerae n16961 O1, El Tor biovar strain. The vasH sequence is variable in isolates lacking ctxA and tcpA genes (ctxAtcpA), and does not differ from the reference in ctxAtcpA+ (with the exception of one strain). The studied toxigenic typical strains and the genovariants have a similar relative level of expression of the vasH gene. In isolates that do not contain the ctxA and tcpA genes, the expression of this gene is comparable to toxigenic strains, and is 3.1 times higher in ctxAtcpA+ strains than that of ctxAtcpA and 2.142.6 times higher than that of toxigenic ones.
Conclusion. The analysis of toxigenic and non-toxigenic V. cholerae O1, biovar El Tor strains isolated in Russia and Ukraine in different periods of the current cholera pandemic confirmed the data of foreign researchers on vasH gene being intact in toxigenic isolates and variable in isolates lacking ctxA and tcpA genes. Meanwhile, the structure of vasH gene has been shown to be identical to that of toxigenic ones in 99% of the studied ctxAtcpA+ strains. The expression of the vasH gene has been detected in all studied strains, being the highest in ctxATtcpA+ strains. Only two non-toxigenic strains presumably synthesizing the functionally inactive VasH protein have been identified.
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19
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Multiple T6SSs, Mobile Auxiliary Modules, and Effectors Revealed in a Systematic Analysis of the Vibrio parahaemolyticus Pan-Genome. mSystems 2022; 7:e0072322. [PMID: 36226968 PMCID: PMC9765294 DOI: 10.1128/msystems.00723-22] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Type VI secretion systems (T6SSs) play a major role in interbacterial competition and in bacterial interactions with eukaryotic cells. The distribution of T6SSs and the effectors they secrete vary between strains of the same bacterial species. Therefore, a pan-genome investigation is required to better understand the T6SS potential of a bacterial species of interest. Here, we performed a comprehensive, systematic analysis of T6SS gene clusters and auxiliary modules found in the pan-genome of Vibrio parahaemolyticus, an emerging pathogen widespread in marine environments. We identified 4 different T6SS gene clusters within genomes of this species; two systems appear to be ancient and widespread, whereas the other 2 systems are rare and appear to have been more recently acquired via horizontal gene transfer. In addition, we identified diverse T6SS auxiliary modules containing putative effectors with either known or predicted toxin domains. Many auxiliary modules are possibly horizontally shared between V. parahaemolyticus genomes, since they are flanked by DNA mobility genes. We further investigated a DUF4225-containing protein encoded on an Hcp auxiliary module, and we showed that it is an antibacterial T6SS effector that exerts its toxicity in the bacterial periplasm, leading to cell lysis. Computational analyses of DUF4225 revealed a widespread toxin domain associated with various toxin delivery systems. Taken together, our findings reveal a diverse repertoire of T6SSs and auxiliary modules in the V. parahaemolyticus pan-genome, as well as novel T6SS effectors and toxin domains that can play a major role in the interactions of this species with other cells. IMPORTANCE Gram-negative bacteria employ toxin delivery systems to mediate their interactions with neighboring cells. Vibrio parahaemolyticus, an emerging pathogen of humans and marine animals, was shown to deploy antibacterial toxins into competing bacteria via the type VI secretion system (T6SS). Here, we analyzed 1,727 V. parahaemolyticus genomes and revealed the pan-genome T6SS repertoire of this species, including the T6SS gene clusters, horizontally shared auxiliary modules, and toxins. We also identified a role for a previously uncharacterized domain, DUF4225, as a widespread antibacterial toxin associated with diverse toxin delivery systems.
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20
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González-Magaña A, Altuna J, Queralt-Martín M, Largo E, Velázquez C, Montánchez I, Bernal P, Alcaraz A, Albesa-Jové D. The P. aeruginosa effector Tse5 forms membrane pores disrupting the membrane potential of intoxicated bacteria. Commun Biol 2022; 5:1189. [PMID: 36335275 PMCID: PMC9637101 DOI: 10.1038/s42003-022-04140-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 10/20/2022] [Indexed: 11/08/2022] Open
Abstract
The type VI secretion system (T6SS) of Pseudomonas aeruginosa injects effector proteins into neighbouring competitors and host cells, providing a fitness advantage that allows this opportunistic nosocomial pathogen to persist and prevail during the onset of infections. However, despite the high clinical relevance of P. aeruginosa, the identity and mode of action of most P. aeruginosa T6SS-dependent effectors remain to be discovered. Here, we report the molecular mechanism of Tse5-CT, the toxic auto-proteolytic product of the P. aeruginosa T6SS exported effector Tse5. Our results demonstrate that Tse5-CT is a pore-forming toxin that can transport ions across the membrane, causing membrane depolarisation and bacterial death. The membrane potential regulates a wide range of essential cellular functions; therefore, membrane depolarisation is an efficient strategy to compete with other microorganisms in polymicrobial environments. The Pseudomonas aeruginosa Type 6 secretion effector Tse5 forms pores in the cytoplasmic membrane when ectopically produced and hence has a bacteriolytic effect by depolarising the inner membrane potential.
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Affiliation(s)
- Amaia González-Magaña
- Fundación Biofísica Bizkaia/Biofisika Bizkaia Fundazioa (FBB) and Departamento de Bioquímica y Biología Molecular, Instituto Biofisika (CSIC, UPV/EHU), University of the Basque Country, 48940, Leioa, Spain
| | - Jon Altuna
- Fundación Biofísica Bizkaia/Biofisika Bizkaia Fundazioa (FBB) and Departamento de Bioquímica y Biología Molecular, Instituto Biofisika (CSIC, UPV/EHU), University of the Basque Country, 48940, Leioa, Spain
| | - María Queralt-Martín
- Laboratory of Molecular Biophysics, Department of Physics, University Jaume I, 12071, Castellón, Spain
| | - Eneko Largo
- Fundación Biofísica Bizkaia/Biofisika Bizkaia Fundazioa (FBB) and Departamento de Bioquímica y Biología Molecular, Instituto Biofisika (CSIC, UPV/EHU), University of the Basque Country, 48940, Leioa, Spain.,Departamento de Inmunología, Microbiología y Parasitología, University of the Basque Country, 48940, Leioa, Spain
| | - Carmen Velázquez
- Fundación Biofísica Bizkaia/Biofisika Bizkaia Fundazioa (FBB) and Departamento de Bioquímica y Biología Molecular, Instituto Biofisika (CSIC, UPV/EHU), University of the Basque Country, 48940, Leioa, Spain
| | - Itxaso Montánchez
- Departamento de Inmunología, Microbiología y Parasitología, University of the Basque Country, 48940, Leioa, Spain
| | - Patricia Bernal
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, 41012, Sevilla, Spain
| | - Antonio Alcaraz
- Laboratory of Molecular Biophysics, Department of Physics, University Jaume I, 12071, Castellón, Spain
| | - David Albesa-Jové
- Fundación Biofísica Bizkaia/Biofisika Bizkaia Fundazioa (FBB) and Departamento de Bioquímica y Biología Molecular, Instituto Biofisika (CSIC, UPV/EHU), University of the Basque Country, 48940, Leioa, Spain. .,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain.
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21
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Carobbi A, Di Nepi S, Fridman CM, Dar Y, Ben‐Yaakov R, Barash I, Salomon D, Sessa G. An antibacterial T6SS in Pantoea agglomerans pv. betae delivers a lysozyme-like effector to antagonize competitors. Environ Microbiol 2022; 24:4787-4802. [PMID: 35706135 PMCID: PMC9796082 DOI: 10.1111/1462-2920.16100] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 06/10/2022] [Indexed: 12/30/2022]
Abstract
The type VI secretion system (T6SS) is deployed by numerous Gram-negative bacteria to deliver toxic effectors into neighbouring cells. The genome of Pantoea agglomerans pv. betae (Pab) phytopathogenic bacteria contains a gene cluster (T6SS1) predicted to encode a complete T6SS. Using secretion and competition assays, we found that T6SS1 in Pab is a functional antibacterial system that allows this pathogen to outcompete rival plant-associated bacteria found in its natural environment. Computational analysis of the T6SS1 gene cluster revealed that antibacterial effector and immunity proteins are encoded within three genomic islands that also harbour arrays of orphan immunity genes or toxin and immunity cassettes. Functional analyses indicated that VgrG, a specialized antibacterial effector, contains a C-terminal catalytically active glucosaminidase domain that is used to degrade prey peptidoglycan. Moreover, we confirmed that a bicistronic unit at the end of the T6SS1 cluster encodes a novel antibacterial T6SS effector and immunity pair. Together, these results demonstrate that Pab T6SS1 is an antibacterial system delivering a lysozyme-like effector to eliminate competitors, and indicate that this bacterium contains additional novel T6SS effectors.
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Affiliation(s)
- Andrea Carobbi
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life SciencesTel‐Aviv UniversityTel‐Aviv
| | - Simone Di Nepi
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life SciencesTel‐Aviv UniversityTel‐Aviv
| | - Chaya M. Fridman
- Department of Clinical Microbiology and Immunology, Sackler Faculty of MedicineTel Aviv UniversityTel Aviv
| | - Yasmin Dar
- Department of Clinical Microbiology and Immunology, Sackler Faculty of MedicineTel Aviv UniversityTel Aviv
| | - Rotem Ben‐Yaakov
- Department of Clinical Microbiology and Immunology, Sackler Faculty of MedicineTel Aviv UniversityTel Aviv
| | - Isaac Barash
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life SciencesTel‐Aviv UniversityTel‐Aviv
| | - Dor Salomon
- Department of Clinical Microbiology and Immunology, Sackler Faculty of MedicineTel Aviv UniversityTel Aviv
| | - Guido Sessa
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life SciencesTel‐Aviv UniversityTel‐Aviv
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22
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Heterologous Assembly of the Type VI Secretion System Empowers Laboratory Escherichia coli with Antimicrobial and Cell Penetration Capabilities. Appl Environ Microbiol 2022; 88:e0130522. [PMID: 36154120 DOI: 10.1128/aem.01305-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The synthetic biology toolbox has amassed a vast number of diverse functional modules, but protein translocation modules for cell penetration and cytosol-to-cytosol delivery remain relatively scarce. The type VI secretion system (T6SS), commonly found in many Gram-negative pathogens, functions as a contractile device to translocate protein toxins to prokaryotic and eukaryotic cells. Here, we have assembled the T6SS of Aeromonas dhakensis, an opportunistic waterborne pathogen, in the common laboratory strain Escherichia coli BL21(DE3). We constructed a series of plasmids (pT6S) carrying the T6SS structural and effector genes under native or tetracycline-inducible promoters, the latter for controlled expression. Using fluorescence microscopy and biochemical analyses, we demonstrate a functional T6SS in E. coli capable of secreting proteins directly into the cytosol of neighboring bacteria and outcompeting a number of drug-resistant pathogens. The heterologous assembly of T6SS not only confers the lab workhorse E. coli with the cytosol-to-cytosol protein delivery capability but also demonstrates the potential for harnessing the T6SS of various pathogens for general protein delivery and antibacterial applications. IMPORTANCE The T6SS is a powerful and versatile protein delivery system. However, the complexity of its macromolecular structure and gene regulation makes it not a trivial task to reconstitute the T6SSs of pathogens in a nonpathogenic host. In this study, we have assembled an inducible T6SS in E. coli BL21(DE3) and demonstrated its functions in protein delivery and antimicrobial activities. The engineered T6SS empowers E. coli to deliver protein cargos into a wide range of prokaryotic and eukaryotic cells.
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Tang MX, Pei TT, Xiang Q, Wang ZH, Luo H, Wang XY, Fu Y, Dong T. Abiotic factors modulate interspecies competition mediated by the type VI secretion system effectors in Vibrio cholerae. THE ISME JOURNAL 2022; 16:1765-1775. [PMID: 35354946 PMCID: PMC9213406 DOI: 10.1038/s41396-022-01228-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 03/08/2022] [Accepted: 03/17/2022] [Indexed: 05/06/2023]
Abstract
Vibrio cholerae, the etiological pathogen of cholera, employs its type VI secretion system (T6SS) as an effective weapon to survive in highly competitive communities. Antibacterial and anti-eukaryotic functions of the T6SS depend on its secreted effectors that target multiple cellular processes. However, the mechanisms that account for effector diversity and different effectiveness during interspecies competition remain elusive. Here we report that environmental cations and temperature play a key role in dictating cellular response and effector effectiveness during interspecies competition mediated by the T6SS of V. cholerae. We found that V. cholerae could employ its cell-wall-targeting effector TseH to outcompete the otherwise resistant Escherichia coli and the V. cholerae immunity deletion mutant ∆tsiH when Mg2+ or Ca2+ was supplemented. Transcriptome and genetic analyses demonstrate that the metal-sensing PhoPQ two-component system is important for Mg2+-dependent sensitivity. Competition analysis in infant mice shows that TseH was active under in vivo conditions. Using a panel of V. cholerae single-effector active mutants, we further show that E. coli also exhibited variable susceptibilities to other T6SS effectors depending on cations and temperatures, respectively. Lastly, V. cholerae effector VasX could sensitize Pseudomonas aeruginosa to its intrinsically resistant antibiotic irgasan in a temperature-dependent manner. Collectively, these findings suggest that abiotic factors, that V. cholerae frequently encounters in natural and host environments, could modulate cellular responses and dictate the competitive fitness conferred by the T6SS effectors in complex multispecies communities.
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Affiliation(s)
- Ming-Xuan Tang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Tong-Tong Pei
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Qi Xiang
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Zeng-Hang Wang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Han Luo
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Xing-Yu Wang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Yang Fu
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Tao Dong
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
- Department of Immunology and Microbiology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, China.
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Ulhuq FR, Mariano G. Bacterial pore-forming toxins. MICROBIOLOGY (READING, ENGLAND) 2022; 168:001154. [PMID: 35333704 PMCID: PMC9558359 DOI: 10.1099/mic.0.001154] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 02/03/2022] [Indexed: 12/11/2022]
Abstract
Pore-forming toxins (PFTs) are widely distributed in both Gram-negative and Gram-positive bacteria. PFTs can act as virulence factors that bacteria utilise in dissemination and host colonisation or, alternatively, they can be employed to compete with rival microbes in polymicrobial niches. PFTs transition from a soluble form to become membrane-embedded by undergoing large conformational changes. Once inserted, they perforate the membrane, causing uncontrolled efflux of ions and/or nutrients and dissipating the protonmotive force (PMF). In some instances, target cells intoxicated by PFTs display additional effects as part of the cellular response to pore formation. Significant progress has been made in the mechanistic description of pore formation for the different PFTs families, but in several cases a complete understanding of pore structure remains lacking. PFTs have evolved recognition mechanisms to bind specific receptors that define their host tropism, although this can be remarkably diverse even within the same family. Here we summarise the salient features of PFTs and highlight where additional research is necessary to fully understand the mechanism of pore formation by members of this diverse group of protein toxins.
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Affiliation(s)
- Fatima R. Ulhuq
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Giuseppina Mariano
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK
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Amaya FA, Blondel CJ, Barros-Infante MF, Rivera D, Moreno-Switt AI, Santiviago CA, Pezoa D. Identification of Type VI Secretion Systems Effector Proteins That Contribute to Interbacterial Competition in Salmonella Dublin. Front Microbiol 2022; 13:811932. [PMID: 35222335 PMCID: PMC8867033 DOI: 10.3389/fmicb.2022.811932] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 01/04/2022] [Indexed: 12/12/2022] Open
Abstract
The Type VI Secretion System (T6SS) is a multiprotein device that has emerged as an important fitness and virulence factor for many Gram-negative bacteria through the injection of effector proteins into prokaryotic or eukaryotic cells via a contractile mechanism. While some effector proteins specifically target bacterial or eukaryotic cells, others can target both types of cells (trans-kingdom effectors). In Salmonella, five T6SS gene clusters have been identified within pathogenicity islands SPI-6, SPI-19, SPI-20, SPI-21, and SPI-22, which are differentially distributed among serotypes. Salmonella enterica serotype Dublin (S. Dublin) is a cattle-adapted pathogen that harbors both T6SSSPI-6 and T6SSSPI-19. Interestingly, while both systems have been linked to virulence and host colonization in S. Dublin, an antibacterial activity has not been detected for T6SSSPI-6 in this serotype. In addition, there is limited information regarding the repertoire of effector proteins encoded within T6SSSPI-6 and T6SSSPI-19 gene clusters in S. Dublin. In the present study, we demonstrate that T6SSSPI-6 and T6SSSPI-19 of S. Dublin CT_02021853 contribute to interbacterial competition. Bioinformatic and comparative genomic analyses allowed us to identify genes encoding three candidate antibacterial effectors located within SPI-6 and two candidate effectors located within SPI-19. Each antibacterial effector gene is located upstream of a gene encoding a hypothetic immunity protein, thus conforming an effector/immunity (E/I) module. Of note, the genes encoding these effectors and immunity proteins are widely distributed in Salmonella genomes, suggesting a relevant role in interbacterial competition and virulence. Finally, we demonstrate that E/I modules SED_RS01930/SED_RS01935 (encoded in SPI-6), SED_RS06235/SED_RS06230, and SED_RS06335/SED_RS06340 (both encoded in SPI-19) contribute to interbacterial competition in S. Dublin CT_02021853.
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Affiliation(s)
- Fernando A. Amaya
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Carlos J. Blondel
- Instituto de Ciencias Biomédicas, Facultad de Medicina y Facultad de Ciencias de la Vida, Universidad Andrés Bello, Santiago, Chile
| | | | - Dácil Rivera
- Escuela de Medicina Veterinaria, Facultad de Ciencias de la Vida, Universidad Andrés Bello, Santiago, Chile
| | - Andrea I. Moreno-Switt
- Escuela de Medicina Veterinaria, Facultad de Agronomía e Ingeniería Forestal, Facultad de Ciencias Biológicas y Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
- Millennium Initiative on Collaborative Research on Bacterial Resistance (MICROB-R), Santiago, Chile
| | - Carlos A. Santiviago
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
- *Correspondence: Carlos A. Santiviago, David Pezoa,
| | - David Pezoa
- Escuela de Medicina Veterinaria, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
- *Correspondence: Carlos A. Santiviago, David Pezoa,
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Weaver AI, Alvarez L, Rosch KM, Ahmed A, Wang GS, vanNieuwenhze MS, Cava F, Dörr T. Lytic transglycosylases mitigate periplasmic crowding by degrading soluble cell wall turnover products. eLife 2022; 11:73178. [PMID: 35073258 PMCID: PMC8820737 DOI: 10.7554/elife.73178] [Citation(s) in RCA: 39] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 01/23/2022] [Indexed: 11/25/2022] Open
Abstract
The peptidoglycan cell wall is a predominant structure of bacteria, determining cell shape and supporting survival in diverse conditions. Peptidoglycan is dynamic and requires regulated synthesis of new material, remodeling, and turnover – or autolysis – of old material. Despite exploitation of peptidoglycan synthesis as an antibiotic target, we lack a fundamental understanding of how peptidoglycan synthesis and autolysis intersect to maintain the cell wall. Here, we uncover a critical physiological role for a widely misunderstood class of autolytic enzymes, lytic transglycosylases (LTGs). We demonstrate that LTG activity is essential to survival by contributing to periplasmic processes upstream and independent of peptidoglycan recycling. Defects accumulate in Vibrio cholerae LTG mutants due to generally inadequate LTG activity, rather than absence of specific enzymes, and essential LTG activities are likely independent of protein-protein interactions, as heterologous expression of a non-native LTG rescues growth of a conditional LTG-null mutant. Lastly, we demonstrate that soluble, uncrosslinked, endopeptidase-dependent peptidoglycan chains, also detected in the wild-type, are enriched in LTG mutants, and that LTG mutants are hypersusceptible to the production of diverse periplasmic polymers. Collectively, our results suggest that LTGs prevent toxic crowding of the periplasm with synthesis-derived peptidoglycan polymers and, contrary to prevailing models, that this autolytic function can be temporally separate from peptidoglycan synthesis.
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Affiliation(s)
| | - Laura Alvarez
- Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University
| | - Kelly M Rosch
- Weill Institute for Cell and Molecular Biology, Cornell University
| | - Asraa Ahmed
- Weill Institute for Cell and Molecular Biology, Cornell University
| | | | | | - Felipe Cava
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University
| | - Tobias Dörr
- Weill Institute for Cell and Molecular Biology, Cornell University
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Crisan CV, Chandrashekar H, Everly C, Steinbach G, Hill SE, Yunker PJ, Lieberman RR, Hammer BK. A New Contact Killing Toxin Permeabilizes Cells and Belongs to a Broadly Distributed Protein Family. mSphere 2021; 6:e0031821. [PMID: 34287011 PMCID: PMC8386463 DOI: 10.1128/msphere.00318-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 06/21/2021] [Indexed: 01/12/2023] Open
Abstract
Vibrio cholerae is an aquatic Gram-negative bacterium that causes severe diarrheal cholera disease when ingested by humans. To eliminate competitor cells in both the external environment and inside hosts, V. cholerae uses the type VI secretion system (T6SS). The T6SS is a macromolecular contact-dependent weapon employed by many Gram-negative bacteria to deliver cytotoxic proteins into adjacent cells. In addition to canonical T6SS gene clusters encoded by all sequenced V. cholerae isolates, strain BGT49 encodes another locus, which we named auxiliary (Aux) cluster 4. The Aux 4 cluster is located on a mobile genetic element and can be used by killer cells to eliminate both V. cholerae and Escherichia coli cells in a T6SS-dependent manner. A putative toxin encoded in the cluster, which we name TpeV (type VI permeabilizing effector Vibrio), shares no homology to known proteins and does not contain motifs or domains indicative of function. Ectopic expression of TpeV in the periplasm of E. coli permeabilizes cells and disrupts the membrane potential. Using confocal microscopy, we confirm that susceptible target cells become permeabilized when competed with killer cells harboring the Aux 4 cluster. We also determine that tpiV, the gene located immediately downstream of tpeV, encodes an immunity protein that neutralizes the toxicity of TpeV. Finally, we show that TpeV homologs are broadly distributed across important human, animal, and plant pathogens and are localized in proximity to other T6SS genes. Our results suggest that TpeV is a toxin that belongs to a large family of T6SS proteins. IMPORTANCE Bacteria live in polymicrobial communities where competition for resources and space is essential for survival. Proteobacteria use the T6SS to eliminate neighboring cells and cause disease. However, the mechanisms by which many T6SS toxins kill or inhibit susceptible target cells are poorly understood. The sequence of the TpeV toxin that we describe here is unlike any previously described protein. We demonstrate that it has antimicrobial activity by permeabilizing cells, eliminating membrane potentials, and causing severe cytotoxicity. TpeV homologs are found near known T6SS genes in human, animal, and plant bacterial pathogens, indicating that the toxin is a representative member of a broadly distributed protein family. We propose that TpeV-like toxins contribute to the fitness of many bacteria. Finally, since antibiotic resistance is a critical global health threat, the discovery of new antimicrobial mechanisms could lead to the development of new treatments against resistant strains.
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Affiliation(s)
- Cristian V. Crisan
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Harshini Chandrashekar
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Catherine Everly
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Gabi Steinbach
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, Georgia, USA
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Shannon E. Hill
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Peter J. Yunker
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, Georgia, USA
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Raquel R. Lieberman
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Brian K. Hammer
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, Georgia, USA
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28
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Abstract
Genetic editing has revolutionized biotechnology, but delivery of endonuclease genes as DNA can lead to aberrant integration or overexpression, leading to off-target effects. Here, we develop a mechanism to deliver Cre recombinase as a protein by engineering the bacterial type six secretion system (T6SS). Using multiple T6SS fusion proteins, Aeromonas dhakensis or attenuated Vibrio cholerae donor strains, and a gain-of-function cassette for detecting Cre recombination, we demonstrate successful delivery of active Cre directly into recipient cells. The most efficient transfer was achieved using a truncated version of PAAR2 from V. cholerae, resulting in a relatively small (118-amino-acid) delivery tag. We further demonstrate the versatility of this system by delivering an exogenous effector, TseC, enabling V. cholerae to kill Pseudomonas aeruginosa. This implies that P. aeruginosa is naturally resistant to all native effectors of V. cholerae and that the TseC chaperone protein is not required for its activity. Moreover, it demonstrates that the engineered system can improve T6SS efficacy against specific pathogens, proposing future application in microbiome manipulation or as a next-generation antimicrobial. Inexpensive and easy to produce, this protein delivery system has many potential applications, ranging from studying T6SS effectors to genetic editing.
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29
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Differential Cellular Response to Translocated Toxic Effectors and Physical Penetration by the Type VI Secretion System. Cell Rep 2021; 31:107766. [PMID: 32553162 DOI: 10.1016/j.celrep.2020.107766] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 04/28/2020] [Accepted: 05/21/2020] [Indexed: 01/06/2023] Open
Abstract
The type VI secretion system (T6SS) is a lethal microbial weapon that injects a large needle-like structure carrying toxic effectors into recipient cells through physical penetration. How recipients respond to physical force and effectors remains elusive. Here, we use a series of effector mutants of Vibrio cholerae to determine how T6SS elicits response in Pseudomonas aeruginosa and Escherichia coli. We show that TseL, but no other effectors or physical puncture, triggers the tit-for-tat response of P. aeruginosa H1-T6SS. Although E. coli is sensitive to all periplasmically expressed effectors, P. aeruginosa is most sensitive to TseL alone. We identify a number of stress response pathways that confer protection against TseL. Physical puncture of T6SS has a moderate inhibitory effect only on envelope-impaired tolB and rseA mutants. Our data reveal that recipient cells primarily respond to effector toxicity but not to physical contact, and they rely on the stress response for immunity-independent protection.
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Hussain NAS, Kirchberger PC, Case RJ, Boucher YF. Modular Molecular Weaponry Plays a Key Role in Competition Within an Environmental Vibrio cholerae Population. Front Microbiol 2021; 12:671092. [PMID: 34122386 PMCID: PMC8189183 DOI: 10.3389/fmicb.2021.671092] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 04/06/2021] [Indexed: 11/13/2022] Open
Abstract
The type VI secretion system (T6SS) operons of Vibrio cholerae contain extraordinarily diverse arrays of toxic effector and cognate immunity genes, which are thought to play an important role in the environmental lifestyle and adaptation of this human pathogen. Through the T6SS, proteinaceous "spears" tipped with antibacterial effectors are injected into adjacent cells, killing those not possessing immunity proteins to these effectors. Here, we investigate the T6SS-mediated dynamics of bacterial competition within a single environmental population of V. cholerae. We show that numerous members of a North American V. cholerae population possess strain-specific repertoires of cytotoxic T6SS effector and immunity genes. Using pairwise competition assays, we demonstrate that the vast majority of T6SS-mediated duels end in stalemates between strains with different T6SS repertoires. However, horizontally acquired effector and immunity genes can significantly alter the outcome of these competitions. Frequently observed horizontal gene transfer events can both increase or reduce competition between distantly related strains by homogenizing or diversifying the T6SS repertoire. Our results also suggest temperature-dependent outcomes in T6SS competition, with environmental isolates faring better against a pathogenic strain under native conditions than under those resembling a host-associated environment. Taken altogether, these interactions produce density-dependent fitness effects and a constant T6SS-mediated arms race in individual V. cholerae populations, which could ultimately preserve intraspecies diversity. Since T6SSs are widespread, we expect within-population diversity in T6SS repertoires and the resulting competitive dynamics to be a common theme in bacterial species harboring this machinery.
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Affiliation(s)
- Nora A. S. Hussain
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Paul C. Kirchberger
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, United States
| | - Rebecca J. Case
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
- Singapore Centre for Environmental Life Sciences Engineering (SCELSE), Nanyang Technological University, Singapore, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Yann F. Boucher
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
- Singapore Centre for Environmental Life Sciences Engineering (SCELSE), Nanyang Technological University, Singapore, Singapore
- Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore
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31
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Zhang A, Han Y, Huang Y, Hu X, Liu P, Liu X, Kan B, Liang W. vgrG is separately transcribed from hcp in T6SS orphan clusters and is under the regulation of IHF and HapR. Biochem Biophys Res Commun 2021; 559:15-20. [PMID: 33932896 DOI: 10.1016/j.bbrc.2021.04.092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 04/21/2021] [Indexed: 11/29/2022]
Abstract
V. cholerae, the causative agent of cholera epidemic, and V. fluvialis, the emerging foodborne pathogen, share highly homologous T6SS consisting of one large cluster and two small orphan or auxiliary clusters, and each of which was generally recognized as one operon. Here, we showed that the genes in each of the small clusters are organized into two transcriptional units. Specifically, the inner tube coding gene hcp/tssD is highly transcribed as one monocistron, while the tip component vgrG/tssI and its downstream effector and immunity genes are in one polycistron with very low transcriptional level. This conclusion is supported by qPCR analysis of mRNA abundance, reporter fusion analysis and transcriptional unit definition with RT-PCR analysis. Taking tssI2_a of V. fluvialis as an example, we further demonstrated that quorum sensing (QS) regulator HapR and global regulator IHF activate vgrG/tssI transcription by directly binding to its promoter region. Taken together, current studies deepen our understanding of T6SS system, highlighting its regulatory complexity during functional execution process.
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Affiliation(s)
- Anran Zhang
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Yu Han
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Yuanming Huang
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Xiao Hu
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Ping Liu
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Xiaoshu Liu
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Biao Kan
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China.
| | - Weili Liang
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China.
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32
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Bouteiller M, Dupont C, Bourigault Y, Latour X, Barbey C, Konto-Ghiorghi Y, Merieau A. Pseudomonas Flagella: Generalities and Specificities. Int J Mol Sci 2021; 22:ijms22073337. [PMID: 33805191 PMCID: PMC8036289 DOI: 10.3390/ijms22073337] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 03/22/2021] [Accepted: 03/22/2021] [Indexed: 12/21/2022] Open
Abstract
Flagella-driven motility is an important trait for bacterial colonization and virulence. Flagella rotate and propel bacteria in liquid or semi-liquid media to ensure such bacterial fitness. Bacterial flagella are composed of three parts: a membrane complex, a flexible-hook, and a flagellin filament. The most widely studied models in terms of the flagellar apparatus are E. coli and Salmonella. However, there are many differences between these enteric bacteria and the bacteria of the Pseudomonas genus. Enteric bacteria possess peritrichous flagella, in contrast to Pseudomonads, which possess polar flagella. In addition, flagellar gene expression in Pseudomonas is under a four-tiered regulatory circuit, whereas enteric bacteria express flagellar genes in a three-step manner. Here, we use knowledge of E. coli and Salmonella flagella to describe the general properties of flagella and then focus on the specificities of Pseudomonas flagella. After a description of flagellar structure, which is highly conserved among Gram-negative bacteria, we focus on the steps of flagellar assembly that differ between enteric and polar-flagellated bacteria. In addition, we summarize generalities concerning the fuel used for the production and rotation of the flagellar macromolecular complex. The last part summarizes known regulatory pathways and potential links with the type-six secretion system (T6SS).
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Affiliation(s)
- Mathilde Bouteiller
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Charly Dupont
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Yvann Bourigault
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Xavier Latour
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Corinne Barbey
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Yoan Konto-Ghiorghi
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Annabelle Merieau
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
- Correspondence:
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Crisan CV, Nichols HL, Wiesenfeld S, Steinbach G, Yunker PJ, Hammer BK. Glucose confers protection to Escherichia coli against contact killing by Vibrio cholerae. Sci Rep 2021; 11:2935. [PMID: 33536444 PMCID: PMC7858629 DOI: 10.1038/s41598-021-81813-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 12/18/2020] [Indexed: 01/30/2023] Open
Abstract
Evolutionary arms races are broadly prevalent among organisms including bacteria, which have evolved defensive strategies against various attackers. A common microbial aggression mechanism is the type VI secretion system (T6SS), a contact-dependent bacterial weapon used to deliver toxic effector proteins into adjacent target cells. Sibling cells constitutively express immunity proteins that neutralize effectors. However, less is known about factors that protect non-sibling bacteria from T6SS attacks independently of cognate immunity proteins. In this study, we observe that human Escherichia coli commensal strains sensitive to T6SS attacks from Vibrio cholerae are protected when co-cultured with glucose. We confirm that glucose does not impair V. cholerae T6SS activity. Instead, we find that cells lacking the cAMP receptor protein (CRP), which regulates expression of hundreds of genes in response to glucose, survive significantly better against V. cholerae T6SS attacks even in the absence of glucose. Finally, we show that the glucose-mediated T6SS protection varies with different targets and killers. Our findings highlight the first example of an extracellular small molecule modulating a genetically controlled response for protection against T6SS attacks. This discovery may have major implications for microbial interactions during pathogen-host colonization and survival of bacteria in environmental communities.
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Affiliation(s)
- Cristian V Crisan
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
| | - Holly L Nichols
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
| | - Sophia Wiesenfeld
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
| | - Gabi Steinbach
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
- School of Physics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Peter J Yunker
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
- School of Physics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Brian K Hammer
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA.
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA.
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34
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Agrobacterium tumefaciens Deploys a Versatile Antibacterial Strategy To Increase Its Competitiveness. J Bacteriol 2021; 203:JB.00490-20. [PMID: 33168638 PMCID: PMC7811202 DOI: 10.1128/jb.00490-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 11/02/2020] [Indexed: 12/28/2022] Open
Abstract
The type VI secretion system (T6SS) is a widespread antibacterial weapon capable of secreting multiple effectors for inhibition of competitor cells. Most of the effectors in the system share the same purpose of target intoxication, but the rationale for maintaining various types of effectors in a species is not well studied. In this study, we showed that a peptidoglycan amidase effector in Agrobacterium tumefaciens, Tae, cleaves d-Ala-meso-diaminopimelic acid (mDAP) and d-Glu bonds in peptidoglycan and is able to suppress the growth of Escherichia coli recipient cells. The growth suppression was effective only under the condition in which E. coli cells are actively growing. In contrast, the Tde DNase effectors in the strain possessed a dominant killing effect under carbon starvation. Microscopic analysis showed that Tde triggers cell elongation and DNA degradation, while Tae causes cell enlargement without DNA damage in E. coli recipient cells. In a rich medium, A. tumefaciens harboring only functional Tae was able to maintain competitiveness among E. coli and its own sibling cells. Growth suppression and the competitive advantage of A. tumefaciens were abrogated when recipient cells produced the Tae-specific immunity protein Tai. Given that Tae is highly conserved among A. tumefaciens strains, the combination of Tae and Tde effectors could allow A. tumefaciens to better compete with various competitors by increasing its survival during changing environmental conditions.IMPORTANCE The T6SS encodes multiple effectors with diverse functions, but little is known about the biological significance of harboring such a repertoire of effectors. We reported that the T6SS antibacterial activity of the plant pathogen Agrobacterium tumefaciens can be enhanced under carbon starvation or when recipient cell wall peptidoglycan is disturbed. This led to a newly discovered role for the T6SS peptidoglycan amidase Tae effector in providing a growth advantage dependent on the growth status of the target cell. This is in contrast to the Tde DNase effectors that are dominant during carbon starvation. Our study suggests that combining Tae and other effectors could allow A. tumefaciens to increase its competitiveness among changing environmental conditions.
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35
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Jurėnas D, Journet L. Activity, delivery, and diversity of Type VI secretion effectors. Mol Microbiol 2020; 115:383-394. [PMID: 33217073 DOI: 10.1111/mmi.14648] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/10/2020] [Accepted: 11/13/2020] [Indexed: 12/28/2022]
Abstract
The bacterial type VI secretion system (T6SS) system is a contractile secretion apparatus that delivers proteins to neighboring bacterial or eukaryotic cells. Antibacterial effectors are mostly toxins that inhibit the growth of other species and help to dominate the niche. A broad variety of these toxins cause cell lysis of the prey cell by disrupting the cell envelope. Other effectors are delivered into the cytoplasm where they affect DNA integrity, cell division or exhaust energy resources. The modular nature of T6SS machinery allows different means of recruitment of toxic effectors to secreted inner tube and spike components that act as carriers. Toxic effectors can be translationally fused to the secreted components or interact with them through specialized structural domains. These interactions can also be assisted by dedicated chaperone proteins. Moreover, conserved sequence motifs in effector-associated domains are subject to genetic rearrangements and therefore engage in the diversification of the arsenal of toxic effectors. This review discusses the diversity of T6SS secreted toxins and presents current knowledge about their loading on the T6SS machinery.
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Affiliation(s)
- Dukas Jurėnas
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université-CNRS, UMR 7255, Marseille, France
| | - Laure Journet
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université-CNRS, UMR 7255, Marseille, France
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Santoriello FJ, Michel L, Unterweger D, Pukatzki S. Pandemic Vibrio cholerae shuts down site-specific recombination to retain an interbacterial defence mechanism. Nat Commun 2020; 11:6246. [PMID: 33288753 PMCID: PMC7721734 DOI: 10.1038/s41467-020-20012-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 11/06/2020] [Indexed: 12/18/2022] Open
Abstract
Vibrio cholerae is an aquatic microbe that can be divided into three subtypes: harmless environmental strains, localised pathogenic strains, and pandemic strains causing global cholera outbreaks. Each type has a contact-dependent type VI secretion system (T6SS) that kills neighbouring competitors by translocating unique toxic effector proteins. Pandemic isolates possess identical effectors, indicating that T6SS effectors may affect pandemicity. Here, we show that one of the T6SS gene clusters (Aux3) exists in two states: a mobile, prophage-like element in a small subset of environmental strains, and a truncated Aux3 unique to and conserved in pandemic isolates. Environmental Aux3 can be readily excised from and integrated into the genome via site-specific recombination, whereas pandemic Aux3 recombination is reduced. Our data suggest that environmental Aux3 acquisition conferred increased competitive fitness to pre-pandemic V. cholerae, leading to grounding of the element in the chromosome and propagation throughout the pandemic clade. Vibrio cholerae uses a type VI secretion system (T6SS) to kill neighbouring competitors. Here, Santoriello et al. show that a T6SS gene cluster (Aux3) exists as a mobile, prophage-like element in some environmental strains, and as a stable truncated form in pandemic isolates. They propose that Aux3 acquisition increased competitive fitness of pre-pandemic V. cholerae.
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Affiliation(s)
- Francis J Santoriello
- Department of Immunology and Microbiology, University of Colorado Denver Anschutz Medical Campus, 13001 E 17th Pl, Aurora, CO, 80045, USA.,Department of Biology, The City College of New York, 160 Convent Ave, New York, NY, 10031, USA
| | - Lina Michel
- Department of Immunology and Microbiology, University of Colorado Denver Anschutz Medical Campus, 13001 E 17th Pl, Aurora, CO, 80045, USA.,Heidelberg University, Grabengasse 1, 69117, Heidelberg, Germany
| | - Daniel Unterweger
- Institute for Experimental Medicine, Kiel University, Michaelisstraße 5, 24105, Kiel, Germany.,Max Planck Institute for Evolutionary Biology, August-Thienemann-Straße 2, 24306, Plön, Germany
| | - Stefan Pukatzki
- Department of Immunology and Microbiology, University of Colorado Denver Anschutz Medical Campus, 13001 E 17th Pl, Aurora, CO, 80045, USA. .,Department of Biology, The City College of New York, 160 Convent Ave, New York, NY, 10031, USA.
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Steinbach G, Crisan C, Ng SL, Hammer BK, Yunker PJ. Accumulation of dead cells from contact killing facilitates coexistence in bacterial biofilms. J R Soc Interface 2020; 17:20200486. [PMID: 33292099 PMCID: PMC7811593 DOI: 10.1098/rsif.2020.0486] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 11/12/2020] [Indexed: 02/06/2023] Open
Abstract
Bacterial communities are governed by a wide variety of social interactions, some of which are antagonistic with potential significance for bacterial warfare. Several antagonistic mechanisms, such as killing via the type VI secretion system (T6SS), require killer cells to directly contact target cells. The T6SS is hypothesized to be a highly potent weapon, capable of facilitating the invasion and defence of bacterial populations. However, we find that the efficacy of contact killing is severely limited by the material consequences of cell death. Through experiments with Vibrio cholerae strains that kill via the T6SS, we show that dead cell debris quickly accumulates at the interface that forms between competing strains, preventing physical contact and thus preventing killing. While previous experiments have shown that T6SS killing can reduce a population of target cells by as much as 106-fold, we find that, as a result of the formation of dead cell debris barriers, the impact of contact killing depends sensitively on the initial concentration of killer cells. Killer cells are incapable of invading or eliminating competitors on a community level. Instead, bacterial warfare itself can facilitate coexistence between nominally antagonistic strains. While a variety of defensive strategies against microbial warfare exist, the material consequences of cell death provide target cells with their first line of defence.
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Affiliation(s)
- Gabi Steinbach
- School of Physics, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
| | - Cristian Crisan
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Siu Lung Ng
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Brian K. Hammer
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Peter J. Yunker
- School of Physics, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA
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38
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Deng Y, Zhang Y, Chen H, Xu L, Wang Q, Feng J. Gut-Liver Immune Response and Gut Microbiota Profiling Reveal the Pathogenic Mechanisms of Vibrio harveyi in Pearl Gentian Grouper ( Epinephelus lanceolatus ♂ × E. fuscoguttatus ♀). Front Immunol 2020; 11:607754. [PMID: 33324424 PMCID: PMC7727329 DOI: 10.3389/fimmu.2020.607754] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 10/29/2020] [Indexed: 12/20/2022] Open
Abstract
Vibrio harveyi causes vibriosis in nearly 70% of grouper (Epinephelus sp.), seriously limiting grouper culture. As well as directly inhibiting pathogens, the gut microbiota plays critical roles in immune homeostasis and provides essential health benefits to its host. However, there is still little information about the variations in the immune response to V. harveyi infection and the gut microbiota of grouper. To understand the virulence mechanism of V. harveyi in the pearl gentian grouper, we investigated the variations in the pathological changes, immune responses, and gut bacterial communities of pearl gentian grouper after exposure to differently virulent V. harveyi strains. Obvious histopathological changes were detected in heart, kidney, and liver. In particular, nodules appeared and huge numbers of V. harveyi cells colonized the liver at 12 h postinfection (hpi) with highly virulent V. harveyi. Although no V. harveyi was detected in the gut, the infection simultaneously induced a gut-liver immune response. In particular, the expression of 8 genes associated with cellular immune processes, including genes encoding inflammatory cytokines and receptors, and pattern recognition proteins, was markedly induced by V. harveyi infection, especially with the highly virulent V. harveyi strain. V. harveyi infection also induced significant changes in gut bacterial community, in which Vibrio and Photobacterium increased but Bradyrhizobium, Lactobacillus, Blautia, and Faecalibaculum decreased in the group infected with the highly virulent strain, with accounting for 82.01% dissimilarity. Correspondingly, four bacterial functions related to bacterial pathogenesis were increased by infection with highly virulent V. harveyi, whereas functions involving metabolism and genetic information processing were reduced. These findings indicate that V. harveyi colonizes the liver and induces a gut-liver immune response that substantially disrupts the composition of and interspecies interactions in the bacterial community in fish gut, thereby altering the gut-microbiota-mediated functions and inducing fish death.
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Affiliation(s)
- Yiqin Deng
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China.,Tropical Aquaculture Research and Development Centre, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Hainan, China
| | - Yaqiu Zhang
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China.,College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China
| | - Haoxiang Chen
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China.,College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China
| | - Liwen Xu
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China
| | - Qian Wang
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China
| | - Juan Feng
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China.,Tropical Aquaculture Research and Development Centre, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Hainan, China
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39
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Liu Y, Zhang Z, Wang F, Li DD, Li YZ. Identification of type VI secretion system toxic effectors using adaptors as markers. Comput Struct Biotechnol J 2020; 18:3723-3733. [PMID: 33304467 PMCID: PMC7714669 DOI: 10.1016/j.csbj.2020.11.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 10/31/2020] [Accepted: 11/02/2020] [Indexed: 12/18/2022] Open
Abstract
Each class of adaptors can be used as an effective marker to identify T6SS effectors. The PRK06147 homolog may be a novel adaptor. 1356 putative toxic effectors related to adaptors from 92 families were identified.
Toxic effectors secreted by the type VI secretion system (T6SS) facilitate interbacterial warfare, as well as pathogenesis toward humans, animals and plants. However, systematically predicting T6SS effectors remains challenging due to their sequence and functional diversity. In this study, we systematically identified putative T6SS toxic effectors in prokaryotic genomes on the basis of the observation that genes encoding adaptor proteins and genes encoding cognate effector proteins are generally adjacent in the genome. Adaptor proteins are mediators that help to load their cognate effectors onto the T6SS spike complex. The contextual genes of the known adaptor proteins (DUF1795, DUF2169 or DUF4123) all exhibited a high proportion of encoding T6SS spike complex protein (VgrG or PAAR) and effector proteins. On the basis of the genomic context, we found that PRK06147 might be a novel adaptor protein. These four adaptors are widely distributed among the bacterial genomes. From neighbors of 5297 adaptor genes, we identified 1356 putative effector genes from 92 different families, and two-thirds were currently annotated as hypothetical proteins or as having unknown functions. Our results indicate that each class of adaptors can be used as an effective marker to identify T6SS toxic effectors, moreover, this approach can promote the discovery of new effectors.
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Affiliation(s)
- Ya Liu
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Zheng Zhang
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao 266237, China.,Suzhou Research Institute, Shandong University, Suzhou 215123, China
| | - Feng Wang
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Dan-Dan Li
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Yue-Zhong Li
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao 266237, China
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40
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Liu L, Song L, Deng R, Lan R, Jin W, Tran Van Nhieu G, Cao H, Liu Q, Xiao Y, Li X, Meng G, Ren Z. Citrobacter freundii Activation of NLRP3 Inflammasome via the Type VI Secretion System. J Infect Dis 2020; 223:2174-2185. [PMID: 33151309 DOI: 10.1093/infdis/jiaa692] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 11/03/2020] [Indexed: 12/27/2022] Open
Abstract
Citrobacter freundii is a significant cause of human infections, responsible for food poisoning, diarrhea, and urinary tract infections. We previously identified a highly cytotoxic and adhesive C. freundii strain CF74 expressing a type VI secretion system (T6SS). In this study, we showed that in mice-derived macrophages, C. freundii CF74 activated the Nucleotide Oligomerization Domain -Like Receptor Family, Pyrin Domain Containing 3(NLRP3) inflammasomes in a T6SS-dependent manner. The C. freundii T6SS activated the inflammasomes mainly through caspase 1 and mediated pyroptosis of macrophages by releasing the cleaved gasdermin-N domain. The CF74 T6SS was required for flagellin-induced interleukin 1β release by macrophages. We further show that the T6SS tail component and effector, hemolysin co-regulation protein-2 (Hcp-2), was necessary and sufficient to trigger NLRP3 inflammasome activation. In vivo, the T6SS played a key role in mediating interleukin 1β secretion and the survival of mice during C. freundii infection in mice. These findings provide novel insights into the role of T6SS in the pathogenesis of C. freundii.
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Affiliation(s)
- Liyun Liu
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Research Units of Discovery of Unknown Bacteria and Function (2018RU010), Chinese Academy of Medical Sciences, Beijing, China
| | - Liqiong Song
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Research Units of Discovery of Unknown Bacteria and Function (2018RU010), Chinese Academy of Medical Sciences, Beijing, China
| | - Rong Deng
- The Center for Microbes, Development and Health, CAS Key Laboratory of Molecular Virology & Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Ruiting Lan
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Wenjie Jin
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Research Units of Discovery of Unknown Bacteria and Function (2018RU010), Chinese Academy of Medical Sciences, Beijing, China
| | - Guy Tran Van Nhieu
- Calcium Signaling and Microbial Infections, Inserm U1282, Laboratoire de Biologie et Pharmacologie Appliquée, UMR 8113, Ecole Normale Supérieure Paris Saclay, Gif-sur-Yvette, France
| | - Huifang Cao
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China
| | - Qin Liu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China
| | - Yuchun Xiao
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Research Units of Discovery of Unknown Bacteria and Function (2018RU010), Chinese Academy of Medical Sciences, Beijing, China
| | - Xianping Li
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Research Units of Discovery of Unknown Bacteria and Function (2018RU010), Chinese Academy of Medical Sciences, Beijing, China
| | - Guangxun Meng
- The Center for Microbes, Development and Health, CAS Key Laboratory of Molecular Virology & Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Zhihong Ren
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Research Units of Discovery of Unknown Bacteria and Function (2018RU010), Chinese Academy of Medical Sciences, Beijing, China
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41
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Perault AI, Chandler CE, Rasko DA, Ernst RK, Wolfgang MC, Cotter PA. Host Adaptation Predisposes Pseudomonas aeruginosa to Type VI Secretion System-Mediated Predation by the Burkholderia cepacia Complex. Cell Host Microbe 2020; 28:534-547.e3. [PMID: 32755549 PMCID: PMC7554260 DOI: 10.1016/j.chom.2020.06.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 06/05/2020] [Accepted: 06/24/2020] [Indexed: 12/14/2022]
Abstract
Pseudomonas aeruginosa and Burkholderia cepacia complex (Bcc) species are opportunistic lung pathogens of cystic fibrosis (CF) patients. While P. aeruginosa can initiate long-term infections in younger CF patients, Bcc infections only arise in teenagers and adults. Both P. aeruginosa and Bcc use type VI secretion systems (T6SSs) to mediate interbacterial competition. Here, we show P. aeruginosa isolates from teenage and adult CF patients, but not those from young CF patients, are outcompeted by the epidemic Bcc isolate Burkholderia cenocepacia strain AU1054 in a T6SS-dependent manner. The genomes of susceptible P. aeruginosa isolates harbor T6SS-abrogating mutations, the repair of which, in some cases, rendered the isolates resistant. Moreover, seven of eight Bcc strains outcompeted P. aeruginosa strains isolated from the same patients. Our findings suggest certain mutations that arise as P. aeruginosa adapts to the CF lung abrogate T6SS activity, making P. aeruginosa and its human host susceptible to potentially fatal Bcc superinfection.
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Affiliation(s)
- Andrew I Perault
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Courtney E Chandler
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, MD 21201, USA
| | - David A Rasko
- Institute for Genome Sciences, University of Maryland, Baltimore, Baltimore, MD 21201, USA; Department of Microbiology and Immunology, University of Maryland, Baltimore, Baltimore, MD 21201, USA
| | - Robert K Ernst
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, MD 21201, USA
| | - Matthew C Wolfgang
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Marsio Lung Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Peggy A Cotter
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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42
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Drebes Dörr NC, Blokesch M. Interbacterial competition and anti-predatory behaviour of environmental Vibrio cholerae strains. Environ Microbiol 2020; 22:4485-4504. [PMID: 32885535 PMCID: PMC7702109 DOI: 10.1111/1462-2920.15224] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 08/31/2020] [Accepted: 09/01/2020] [Indexed: 12/21/2022]
Abstract
Vibrio cholerae isolates responsible for cholera pandemics represent only a small portion of the diverse strains belonging to this species. Indeed, most V. cholerae are encountered in aquatic environments. To better understand the emergence of pandemic lineages, it is crucial to discern what differentiates pandemic strains from their environmental relatives. Here, we studied the interaction of environmental V. cholerae with eukaryotic predators or competing bacteria and tested the contributions of the haemolysin and the type VI secretion system (T6SS) to those interactions. Both of these molecular weapons are constitutively active in environmental isolates but subject to tight regulation in the pandemic clade. We showed that several environmental isolates resist amoebal grazing and that this anti‐grazing defense relies on the strains' T6SS and its actincross‐linking domain (ACD)‐containing tip protein. Strains lacking the ACD were unable to defend themselves against grazing amoebae but maintained high levels of T6SS‐dependent interbacterial killing. We explored the latter phenotype through whole‐genome sequencing of 14 isolates, which unveiled a wide array of novel T6SS effector and (orphan) immunity proteins. By combining these in silico predictions with experimental validations, we showed that highly similar but non‐identical immunity proteins were insufficient to provide cross‐immunity among those wild strains.
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Affiliation(s)
- Natália C Drebes Dörr
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, CH-1015, Switzerland
| | - Melanie Blokesch
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, CH-1015, Switzerland
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43
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Ramamurthy T, Nandy RK, Mukhopadhyay AK, Dutta S, Mutreja A, Okamoto K, Miyoshi SI, Nair GB, Ghosh A. Virulence Regulation and Innate Host Response in the Pathogenicity of Vibrio cholerae. Front Cell Infect Microbiol 2020; 10:572096. [PMID: 33102256 PMCID: PMC7554612 DOI: 10.3389/fcimb.2020.572096] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 08/19/2020] [Indexed: 02/06/2023] Open
Abstract
The human pathogen Vibrio cholerae is the causative agent of severe diarrheal disease known as cholera. Of the more than 200 "O" serogroups of this pathogen, O1 and O139 cause cholera outbreaks and epidemics. The rest of the serogroups, collectively known as non-O1/non-O139 cause sporadic moderate or mild diarrhea and also systemic infections. Pathogenic V. cholerae circulates between nutrient-rich human gut and nutrient-deprived aquatic environment. As an autochthonous bacterium in the environment and as a human pathogen, V. cholerae maintains its survival and proliferation in these two niches. Growth in the gastrointestinal tract involves expression of several genes that provide bacterial resistance against host factors. An intricate regulatory program involving extracellular signaling inputs is also controlling this function. On the other hand, the ability to store carbon as glycogen facilitates bacterial fitness in the aquatic environment. To initiate the infection, V. cholerae must colonize the small intestine after successfully passing through the acid barrier in the stomach and survive in the presence of bile and antimicrobial peptides in the intestinal lumen and mucus, respectively. In V. cholerae, virulence is a multilocus phenomenon with a large functionally associated network. More than 200 proteins have been identified that are functionally linked to the virulence-associated genes of the pathogen. Several of these genes have a role to play in virulence and/or in functions that have importance in the human host or the environment. A total of 524 genes are differentially expressed in classical and El Tor strains, the two biotypes of V. cholerae serogroup O1. Within the host, many immune and biological factors are able to induce genes that are responsible for survival, colonization, and virulence. The innate host immune response to V. cholerae infection includes activation of several immune protein complexes, receptor-mediated signaling pathways, and other bactericidal proteins. This article presents an overview of regulation of important virulence factors in V. cholerae and host response in the context of pathogenesis.
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Affiliation(s)
| | - Ranjan K Nandy
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Asish K Mukhopadhyay
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Shanta Dutta
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Ankur Mutreja
- Global Health-Infectious Diseases, Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Keinosuke Okamoto
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.,Collaborative Research Center of Okayama University for Infectious Diseases in India, National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Shin-Ichi Miyoshi
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - G Balakrish Nair
- Microbiome Laboratory, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
| | - Amit Ghosh
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India
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44
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A membrane-depolarizing toxin substrate of the Staphylococcus aureus type VII secretion system mediates intraspecies competition. Proc Natl Acad Sci U S A 2020; 117:20836-20847. [PMID: 32769205 PMCID: PMC7456083 DOI: 10.1073/pnas.2006110117] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The type VII protein secretion system (T7SS) is conserved across Staphylococcus aureus strains and plays important roles in virulence and interbacterial competition. To date, only one T7SS substrate protein, encoded in a subset of S. aureus genomes, has been functionally characterized. Here, using an unbiased proteomic approach, we identify TspA as a further T7SS substrate. TspA is encoded distantly from the T7SS gene cluster and is found across all S. aureus strains as well as in Listeria and Enterococci. Heterologous expression of TspA from S. aureus strain RN6390 indicates its C-terminal domain is toxic when targeted to the Escherichia coli periplasm and that it depolarizes the cytoplasmic membrane. The membrane-depolarizing activity is alleviated by coproduction of the membrane-bound TsaI immunity protein, which is encoded adjacent to tspA on the S. aureus chromosome. Using a zebrafish hindbrain ventricle infection model, we demonstrate that the T7SS of strain RN6390 promotes bacterial replication in vivo, and deletion of tspA leads to increased bacterial clearance. The toxin domain of TspA is highly polymorphic and S. aureus strains encode multiple tsaI homologs at the tspA locus, suggestive of additional roles in intraspecies competition. In agreement, we demonstrate TspA-dependent growth inhibition of RN6390 by strain COL in the zebrafish infection model that is alleviated by the presence of TsaI homologs.
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45
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Kim N, Kim JJ, Kim I, Mannaa M, Park J, Kim J, Lee H, Lee S, Park D, Sul WJ, Seo Y. Type VI secretion systems of plant-pathogenic Burkholderia glumae BGR1 play a functionally distinct role in interspecies interactions and virulence. MOLECULAR PLANT PATHOLOGY 2020; 21:1055-1069. [PMID: 32643866 PMCID: PMC7368126 DOI: 10.1111/mpp.12966] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 05/28/2020] [Accepted: 05/31/2020] [Indexed: 05/02/2023]
Abstract
In the environment, bacteria show close association, such as interspecies interaction, with other bacteria as well as host organisms. The type VI secretion system (T6SS) in gram-negative bacteria is involved in bacterial competition or virulence. The plant pathogen Burkholderia glumae BGR1, causing bacterial panicle blight in rice, has four T6SS gene clusters. The presence of at least one T6SS gene cluster in an organism indicates its distinct role, like in the bacterial and eukaryotic cell targeting system. In this study, deletion mutants targeting four tssD genes, which encode the main component of T6SS needle formation, were constructed to functionally dissect the four T6SSs in B. glumae BGR1. We found that both T6SS group_4 and group_5, belonging to the eukaryotic targeting system, act independently as bacterial virulence factors toward host plants. In contrast, T6SS group_1 is involved in bacterial competition by exerting antibacterial effects. The ΔtssD1 mutant lost the antibacterial effect of T6SS group_1. The ΔtssD1 mutant showed similar virulence as the wild-type BGR1 in rice because the ΔtssD1 mutant, like the wild-type BGR1, still has key virulence factors such as toxin production towards rice. However, metagenomic analysis showed different bacterial communities in rice infected with the ΔtssD1 mutant compared to wild-type BGR1. In particular, the T6SS group_1 controls endophytic plant-associated bacteria such as Luteibacter and Dyella in rice plants and may have an advantage in competing with endophytic plant-associated bacteria for settlement inside rice plants in the environment. Thus, B. glumae BGR1 causes disease using T6SSs with functionally distinct roles.
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Affiliation(s)
- Namgyu Kim
- Department of Integrated Biological SciencePusan National UniversityBusanKorea
| | - Jin Ju Kim
- Department of Systems BiotechnologyChung‐Ang UniversityAnseongKorea
| | - Inyoung Kim
- Department of Integrated Biological SciencePusan National UniversityBusanKorea
| | - Mohamed Mannaa
- Department of Integrated Biological SciencePusan National UniversityBusanKorea
| | - Jungwook Park
- Department of Integrated Biological SciencePusan National UniversityBusanKorea
| | - Juyun Kim
- Department of Integrated Biological SciencePusan National UniversityBusanKorea
| | - Hyun‐Hee Lee
- Department of Integrated Biological SciencePusan National UniversityBusanKorea
| | | | | | - Woo Jun Sul
- Department of Systems BiotechnologyChung‐Ang UniversityAnseongKorea
| | - Young‐Su Seo
- Department of Integrated Biological SciencePusan National UniversityBusanKorea
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46
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Hernandez RE, Gallegos‐Monterrosa R, Coulthurst SJ. Type
VI
secretion system effector proteins: Effective weapons for bacterial competitiveness. Cell Microbiol 2020; 22:e13241. [DOI: 10.1111/cmi.13241] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 06/08/2020] [Accepted: 06/15/2020] [Indexed: 12/31/2022]
Affiliation(s)
- Ruth E. Hernandez
- Division of Molecular Microbiology, School of Life SciencesUniversity of Dundee Dundee UK
| | | | - Sarah J. Coulthurst
- Division of Molecular Microbiology, School of Life SciencesUniversity of Dundee Dundee UK
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47
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Ruhe ZC, Low DA, Hayes CS. Polymorphic Toxins and Their Immunity Proteins: Diversity, Evolution, and Mechanisms of Delivery. Annu Rev Microbiol 2020; 74:497-520. [PMID: 32680451 DOI: 10.1146/annurev-micro-020518-115638] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
All bacteria must compete for growth niches and other limited environmental resources. These existential battles are waged at several levels, but one common strategy entails the transfer of growth-inhibitory protein toxins between competing cells. These antibacterial effectors are invariably encoded with immunity proteins that protect cells from intoxication by neighboring siblings. Several effector classes have been described, each designed to breach the cell envelope of target bacteria. Although effector architectures and export pathways tend to be clade specific, phylogenetically distant species often deploy closely related toxin domains. Thus, diverse competition systems are linked through a common reservoir of toxin-immunity pairs that is shared via horizontal gene transfer. These toxin-immunity protein pairs are extraordinarily diverse in sequence, and this polymorphism underpins an important mechanism of self/nonself discrimination in bacteria. This review focuses on the structures, functions, and delivery mechanisms of polymorphic toxin effectors that mediate bacterial competition.
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Affiliation(s)
- Zachary C Ruhe
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA;
| | - David A Low
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA; .,Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106, USA
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA; .,Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106, USA
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48
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Crisan CV, Hammer BK. The
Vibrio cholerae
type VI secretion system: toxins, regulators and consequences. Environ Microbiol 2020; 22:4112-4122. [DOI: 10.1111/1462-2920.14976] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 03/01/2020] [Accepted: 03/02/2020] [Indexed: 12/13/2022]
Affiliation(s)
- Cristian V. Crisan
- Center for Microbial Dynamics and Infection Georgia Institute of Technology Atlanta GA USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology Atlanta GA USA
- School of Biological Sciences, Georgia Institute of Technology Atlanta GA USA
| | - Brian K. Hammer
- Center for Microbial Dynamics and Infection Georgia Institute of Technology Atlanta GA USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology Atlanta GA USA
- School of Biological Sciences, Georgia Institute of Technology Atlanta GA USA
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49
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A comparative genomics methodology reveals a widespread family of membrane-disrupting T6SS effectors. Nat Commun 2020; 11:1085. [PMID: 32109231 PMCID: PMC7046647 DOI: 10.1038/s41467-020-14951-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 02/13/2020] [Indexed: 01/01/2023] Open
Abstract
Gram-negative bacteria deliver effectors via the type VI secretion system (T6SS) to outcompete their rivals. Each bacterial strain carries a different arsenal of effectors; the identities of many remain unknown. Here, we present an approach to identify T6SS effectors encoded in bacterial genomes of interest, without prior knowledge of the effectors’ domain content or genetic neighborhood. Our pipeline comprises a comparative genomics analysis followed by screening using a surrogate T6SS+ strain. Using this approach, we identify an antibacterial effector belonging to the T6SS1 of Vibrio parahaemolyticus, representing a widespread family of T6SS effectors sharing a C-terminal domain that we name Tme (Type VI membrane-disrupting effector). Tme effectors function in the periplasm where they intoxicate bacteria by disrupting membrane integrity. We believe our approach can be scaled up to identify additional T6SS effectors in various bacterial genera. Gram-negative bacteria deliver effectors via the type VI secretion system (T6SS) to outcompete their rivals. Here, Fridman et al. present an approach to identify T6SS effectors encoded in bacterial genomes without prior knowledge of their domain content or genetic neighbourhood, and identify a new family of membrane-disrupting effectors.
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50
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Hersch SJ, Watanabe N, Stietz MS, Manera K, Kamal F, Burkinshaw B, Lam L, Pun A, Li M, Savchenko A, Dong TG. Envelope stress responses defend against type six secretion system attacks independently of immunity proteins. Nat Microbiol 2020; 5:706-714. [PMID: 32094588 PMCID: PMC7190449 DOI: 10.1038/s41564-020-0672-6] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 01/16/2020] [Indexed: 11/23/2022]
Abstract
The arms race among microbes is a key driver in the evolution of not only the weapons but also defence mechanisms. Many gram-negative bacteria use the type six secretion system (T6SS) to deliver toxic effectors directly into neighbouring cells. Defence against effectors requires cognate immunity proteins. However, here we show immunity-independent protection mediated by envelope stress responses in Escherichia coli and Vibrio cholerae against a V. cholerae T6SS effector, TseH. We demonstrate that TseH is a PAAR-dependent species-specific effector highly potent against Aeromonas species but not against its V. cholerae immunity mutant or E. coli. Structural analysis reveals TseH is likely a NlpC/P60 family cysteine endopeptidase. We determine that two envelope stress response pathways, Rcs and BaeSR, protect E. coli from TseH toxicity by mechanisms including capsule synthesis. The two-component system WigKR (VxrAB) is critical for protecting V. cholerae from its own T6SS despite expressing immunity genes. WigR also regulates T6SS expression, suggesting a dual role in attack and defence. This deepens our understanding of how bacteria survive T6SS attacks and suggests that defending against the T6SS represents a major selective pressure driving the evolution of species-specific effectors and protective mechanisms mediated by envelope stress responses and capsule synthesis.
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Affiliation(s)
- Steven J Hersch
- Department of Ecosystem and Public Health, University of Calgary, Calgary, Canada
| | - Nobuhiko Watanabe
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Canada
| | - Maria Silvina Stietz
- Department of Ecosystem and Public Health, University of Calgary, Calgary, Canada
| | - Kevin Manera
- Department of Ecosystem and Public Health, University of Calgary, Calgary, Canada
| | - Fatima Kamal
- Department of Ecosystem and Public Health, University of Calgary, Calgary, Canada
| | - Brianne Burkinshaw
- Department of Ecosystem and Public Health, University of Calgary, Calgary, Canada
| | - Linh Lam
- Department of Ecosystem and Public Health, University of Calgary, Calgary, Canada
| | - Alexander Pun
- Department of Ecosystem and Public Health, University of Calgary, Calgary, Canada
| | - Meixin Li
- Department of Ecosystem and Public Health, University of Calgary, Calgary, Canada
| | - Alexei Savchenko
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Canada
| | - Tao G Dong
- Department of Ecosystem and Public Health, University of Calgary, Calgary, Canada. .,State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
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