Two Type VI Secretion Systems of Enterobacter cloacae Are Required for Bacterial Competition, Cell Adherence, and Intestinal Colonization

The type VI secretion system (T6SS) plays a major role in mediating interbacterial competition and might contribute to virulence in plant pathogenic bacteria. However, the role of T6SS in Erwinia amylovora remains unknown. In this study, 33 deletion mutants within three T6SS clusters were generated in E. amylovora strain NCPPB1665. Our results showed that all 33 mutants displayed reduced antibacterial activities against Escherichia coli as compared with that of the wild-type (WT) strain, indicating that Erwinia amylovora T6SS are functional. Of the 33 mutants, 19 exhibited reduced virulence on immature pear fruit as compared with that of the WT strain. Among them, 6, 1, and 12 genes belonged to T6SS-1, T6SS-2, and T6SS-3 clusters, respectively. Interestingly, these 19 mutants also produced less amylovoran or levan or both. These findings suggest that E. amylovora T6SS play a role in bacterial competition and virulence possibly by influencing exopolysaccharide production.

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RsmA and AmrZ orchestrate the assembly of all three type VI secretion systems in Pseudomonas aeruginosa

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1700286114 ◽

2017 ◽

Vol 114 (29) ◽

pp. 7707-7712 ◽

Cited By ~ 59

Author(s):

Luke P. Allsopp ◽

Thomas E. Wood ◽

Sophie A. Howard ◽

Federica Maggiorelli ◽

Laura M. Nolan ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Regulatory Elements ◽

Negative Regulator ◽

Type Vi Secretion System ◽

Secretion Systems ◽

Bacterial Competition ◽

Type Vi Secretion ◽

Poor Understanding ◽

Gun Firing

The type VI secretion system (T6SS) is a weapon of bacterial warfare and host cell subversion. The Gram-negative pathogen Pseudomonas aeruginosa has three T6SSs involved in colonization, competition, and full virulence. H1-T6SS is a molecular gun firing seven toxins, Tse1–Tse7, challenging survival of other bacteria and helping P. aeruginosa to prevail in specific niches. The H1-T6SS characterization was facilitated through studying a P. aeruginosa strain lacking the RetS sensor, which has a fully active H1-T6SS, in contrast to the parent. However, study of H2-T6SS and H3-T6SS has been neglected because of a poor understanding of the associated regulatory network. Here we performed a screen to identify H2-T6SS and H3-T6SS regulatory elements and found that the posttranscriptional regulator RsmA imposes a concerted repression on all three T6SS clusters. A higher level of complexity could be observed as we identified a transcriptional regulator, AmrZ, which acts as a negative regulator of H2-T6SS. Overall, although the level of T6SS transcripts is fine-tuned by AmrZ, all T6SS mRNAs are silenced by RsmA. We expanded this concept of global control by RsmA to VgrG spike and T6SS toxin transcripts whose genes are scattered on the chromosome. These observations triggered the characterization of a suite of H2-T6SS toxins and their implication in direct bacterial competition. Our study thus unveils a central mechanism that modulates the deployment of all T6SS weapons that may be simultaneously produced within a single cell.

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Pantoea ananatis Utilizes a Type VI Secretion System for Pathogenesis and Bacterial Competition

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-07-14-0219-r ◽

2015 ◽

Vol 28 (4) ◽

pp. 420-431 ◽

Cited By ~ 28

Author(s):

Divine Y. Shyntum ◽

Jacques Theron ◽

Stephanus N. Venter ◽

Lucy N. Moleleki ◽

Ian K. Toth ◽

...

Keyword(s):

Wild Type Strain ◽

Gene Clusters ◽

Wild Type ◽

Type Vi Secretion System ◽

Secretion Systems ◽

Pantoea Ananatis ◽

Bacterial Competition ◽

Type Vi Secretion ◽

Pineapple Fruit

Type VI secretion systems (T6SSs) are a class of macromolecular machines that are recognized as an important virulence mechanism in several gram-negative bacteria. The genome of Pantoea ananatis LMG 2665T, a pathogen of pineapple fruit and onion plants, carries two gene clusters whose predicted products have homology with T6SS-associated gene products from other bacteria. Nothing is known regarding the role of these T6SS-1 and T6SS-3 gene clusters in the biology of P. ananatis. Here, we present evidence that T6SS-1 plays an important role in the pathogenicity of P. ananatis LMG 2665T in onion plants, while a strain lacking T6SS-3 remains as pathogenic as the wild-type strain. We also investigated the role of the T6SS-1 system in bacterial competition, the results of which indicated that several bacteria compete less efficiently against wild-type LMG 2665T than a strain lacking T6SS-1. Additionally, we demonstrated that these phenotypes of strain LMG 2665T were reliant on the core T6SS products TssA and TssD (Hcp), thus indicating that the T6SS-1 gene cluster encodes a functioning T6SS. Collectively, our data provide the first evidence demonstrating that the T6SS-1 system is a virulence determinant of P. ananatis LMG 2665T and plays a role in bacterial competition.

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Comparative genomics of the type VI secretion systems of Pantoea and Erwinia species reveals the presence of putative effector islands that may be translocated by the VgrG and Hcp proteins

BMC Genomics ◽

10.1186/1471-2164-12-576 ◽

2011 ◽

Vol 12 (1) ◽

Cited By ~ 47

Author(s):

Pieter De Maayer ◽

Stephanus N Venter ◽

Tim Kamber ◽

Brion Duffy ◽

Teresa A Coutinho ◽

...

Keyword(s):

Comparative Genomics ◽

Secretion Systems ◽

Type Vi Secretion ◽

Erwinia Species

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The Roles of Two Type VI Secretion Systems in Cronobacter sakazakii ATCC 12868

Frontiers in Microbiology ◽

10.3389/fmicb.2018.02499 ◽

2018 ◽

Vol 9 ◽

Cited By ~ 7

Author(s):

Min Wang ◽

Hengchun Cao ◽

Qian Wang ◽

Tingting Xu ◽

Xi Guo ◽

...

Keyword(s):

Cronobacter Sakazakii ◽

Secretion Systems ◽

Type Vi Secretion

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A family of T6SS antibacterial effectors related to L,D-transpeptidases targets the Peptidoglycan

Access Microbiology ◽

10.1099/acmi.ac2020.po0033 ◽

2020 ◽

Vol 2 (7A) ◽

Author(s):

Stephanie Sibinelli de Sousa ◽

Julia Takuno Hespanhol ◽

Bruno Matsuyama ◽

Stephane Mesnage ◽

Gianlucca Nicastro ◽

...

Keyword(s):

Cell Envelope ◽

Point Mutations ◽

Time Lapse ◽

Secretion Systems ◽

Bacterial Antagonism ◽

New Family ◽

Type Vi Secretion ◽

Altered Cell ◽

Bacterial Effectors ◽

Insight Into

Type VI secretion systems (T6SSs) are contractile nanomachines widely used by bacteria to intoxicate competitors. Salmonella Typhimurium encodes a T6SS within the Salmonella pathogenicity island 6 (SPI-6) that is used during competition against species of the gut microbiota. We characterized a new SPI-6 T6SS antibacterial effector named Tlde1 (type VI L,D-transpeptidase effector 1). Tlde1 is toxic in target-cell periplasm and its toxicity is neutralized by co-expression with immunity protein Tldi1 (type VI L,D-transpeptidase immunity 1). Time-lapse microscopy revealed that intoxicated cells display altered cell division and lose cell envelope integrity. Bioinformatics analysis showed that Tlde1 is evolutionarily related to L,D-transpeptidases. Point mutations on conserved histidine121 and cysteine131 residues eliminated toxicity. Co-incubation of purified recombinant Tlde1 and peptidoglycan tetrapeptides showed that Tlde1 displays both L,D-carboxypeptidase activity by cleaving GM-tetrapeptides between meso-diaminopimelic acid3 and D-alanine4, and L,D-transpeptidase exchange activity by replacing D-alanine4 for a non-canonical D-amino acid. Tlde1 constitutes a new family of T6SS effectors widespread in Proteobacteria. This work increases our knowledge about the bacterial effectors used in interbacterial competitions and provides molecular insight into a new mechanism of bacterial antagonism.

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The evolution of tit-for-tat in bacteria via the type VI secretion system

Nature Communications ◽

10.1038/s41467-020-19017-z ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

William P. J. Smith ◽

Maj Brodmann ◽

Daniel Unterweger ◽

Yohan Davit ◽

Laurie E. Comstock ◽

...

Keyword(s):

Animal Behavior ◽

Evolutionary Game ◽

Secretion System ◽

Evolutionary Strategy ◽

Type Vi Secretion System ◽

Agent Based ◽

Agent Based Modelling ◽

Bacterial Competition ◽

Type Vi Secretion ◽

Tit For Tat

Abstract Tit-for-tat is a familiar principle from animal behavior: individuals respond in kind to being helped or harmed by others. Remarkably some bacteria appear to display tit-for-tat behavior, but how this evolved is not understood. Here we combine evolutionary game theory with agent-based modelling of bacterial tit-for-tat, whereby cells stab rivals with poisoned needles (the type VI secretion system) after being stabbed themselves. Our modelling shows tit-for-tat retaliation is a surprisingly poor evolutionary strategy, because tit-for-tat cells lack the first-strike advantage of preemptive attackers. However, if cells retaliate strongly and fire back multiple times, we find that reciprocation is highly effective. We test our predictions by competing Pseudomonas aeruginosa (a tit-for-tat species) with Vibrio cholerae (random-firing), revealing that P. aeruginosa does indeed fire multiple times per incoming attack. Our work suggests bacterial competition has led to a particular form of reciprocation, where the principle is that of strong retaliation, or ‘tits-for-tat’.

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Type VI secretion systems of plant‐pathogenic Burkholderia glumae BGR1 play a functionally distinct role in interspecies interactions and virulence

Molecular Plant Pathology ◽

10.1111/mpp.12966 ◽

2020 ◽

Vol 21 (8) ◽

pp. 1055-1069 ◽

Cited By ~ 2

Author(s):

Namgyu Kim ◽

Jin Ju Kim ◽

Inyoung Kim ◽

Mohamed Mannaa ◽

Jungwook Park ◽

...

Keyword(s):

Interspecies Interactions ◽

Secretion Systems ◽

Burkholderia Glumae ◽

Type Vi Secretion ◽

Distinct Role

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Paraburkholderia phymatum STM815 σ54 Controls Utilization of Dicarboxylates, Motility, and T6SS-b Expression

Nitrogen ◽

10.3390/nitrogen1020008 ◽

2020 ◽

Vol 1 (2) ◽

pp. 81-98

Author(s):

Martina Lardi ◽

Yilei Liu ◽

Sebastian Hug ◽

Samanta Bolzan de Campos ◽

Leo Eberl ◽

...

Keyword(s):

Wild Type Strain ◽

Nitrogenase Activity ◽

Secretion Systems ◽

Free Living ◽

Major Life ◽

Life Styles ◽

Type Vi Secretion ◽

Flagellar Biosynthesis ◽

Free Living Conditions

Rhizobia have two major life styles, one as free-living bacteria in the soil, and the other as bacteroids within the root/stem nodules of host legumes where they convert atmospheric nitrogen into ammonia. In the soil, rhizobia have to cope with changing and sometimes stressful environmental conditions, such as nitrogen limitation. In the beta-rhizobial strain Paraburkholderia phymatum STM815, the alternative sigma factor σ54 (or RpoN) has recently been shown to control nitrogenase activity during symbiosis with Phaseolus vulgaris. In this study, we determined P. phymatum’s σ54 regulon under nitrogen-limited free-living conditions. Among the genes significantly downregulated in the absence of σ54, we found a C4-dicarboxylate carrier protein (Bphy_0225), a flagellar biosynthesis cluster (Bphy_2926-64), and one of the two type VI secretion systems (T6SS-b) present in the P. phymatum STM815 genome (Bphy_5978-97). A defined σ54 mutant was unable to grow on C4 dicarboxylates as sole carbon source and was less motile compared to the wild-type strain. Both defects could be complemented by introducing rpoNin trans. Using promoter reporter gene fusions, we also confirmed that the expression of the T6SS-b cluster is regulated by σ54. Accordingly, we show that σ54 affects in vitro competitiveness of P. phymatum STM815 against Paraburkholderia diazotrophica.

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