Presence and absence of type VI secretion systems in bacteria

Unni, Rahul; Pintor, Katherine L.; Diepold, Andreas; Unterweger, Daniel

doi:10.1099/mic.0.001151

Cited by 28 publications

(23 citation statements)

References 151 publications

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“…These can be used in conjunction with theoretical tools to gain further understanding on what rules govern outcome of competition. If the T6SS is a key machine in the resolution of microbial competition, genomic approaches showed that despite a broad distribution across phyla and species, there is no rule on who does or does not pose a T6SS [118]. Trying to figure out the benefit for bacteria of having or not a T6SS would only make sense if we understand which toxins are delivered by these systems, and what are their impact on preys.…”

Section: Discussionmentioning

confidence: 99%

Effectiveness ofPseudomonas aeruginosatype VI secretion system relies on toxin potency and type IV pili-dependent interaction

Rudzite

Endres

Filloux

2022

Preprint

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The type VI secretion system (T6SS) is an antibacterial weapon that is used by numerous Gram-negative bacteria to gain competitive advantage by injecting toxins into adjacent prey cells. Predicting the outcome of a T6SS-dependent competition is not only reliant on presence-absence of the system but instead involves a multiplicity of factors. Pseudomonas aeruginosa possesses 3 distinct T6SSs and a set of more than 20 toxic effectors with diverse functions including disruption of cell wall integrity, degradation of nucleic acids or metabolic impairment. We generated a comprehensive collection of mutants with various degrees of T6SS activity and/or sensitivity to each individual T6SS toxin. By imaging whole mixed bacterial macrocolonies, we then investigated how these P. aeruginosa strains gain a competitive edge in multiple attacker/prey combinations. We observed that the potency of single T6SS toxin varies significantly from one another as measured by monitoring the community structure, with some toxins acting better in synergy or requiring a higher payload. Remarkably the degree of intermixing between preys and attackers is also key to the competition outcome and is driven by the frequency of contact as well as the ability of the prey to move away from the attacker using type IV pili-dependent twitching motility. Finally, we implemented a computational model to better understand how changes in T6SS firing behaviours or cell-cell contacts lead to population level competitive advantages, thus providing conceptual insight applicable to all types of contact-based competition.

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Section: Discussionmentioning

confidence: 99%

Effectiveness ofPseudomonas aeruginosatype VI secretion system relies on toxin potency and type IV pili-dependent interaction

Rudzite

Endres

Filloux

2022

Preprint

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“…T6SS is a complex nanomachine resembling the contractile tail of bacteriophages. It is classified into four subtypes (T6SS i to T6SS iv ) that differ in structure and number of core components ( 9 , 13 ). The canonical T6SS i commonly found in Proteobacteria is composed of at least 14 core components that are assembled in subcomplexes: a cytoplasmic baseplate, an intermembrane complex, a contractile sheath-like structure (VipAB), and an inner tube of polymerized Hcp (hemolysin-coregulated protein) sharpened at its tip by VgrG (valine-glycine repeat protein G) trimers and PAAR (proline-alanine-alanine-arginine) proteins ( 14 – 17 ).…”

Section: Introductionmentioning

confidence: 99%

A Quorum Sensing-Regulated Type VI Secretion System Containing Multiple Nonredundant VgrG Proteins Is Required for Interbacterial Competition in Chromobacterium violaceum

et al. 2022

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“…The T6SS is a complex bacterial secretion system present in many Gram-negative bacteria and used primarily to outcompete foes. The core components of T6SS nanomachines are well conserved at the structural level, and the assembly of these systems seems to be overall similar even in phylogenetically distant T6SSs [61]. A certain diversity has been described, reflected in the presence of accessory components (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…This provides a clear insight into the importance of controlling and monitoring T6SSs. In fact, in a recent review on the presence and absence of T6SS in bacteria, the consequences of not having a strictly regulated T6SS were discussed as a possible cause of losing this powerful antimicrobial weapon [61]. Thus, we could consider that the master regulators described in this study will allow us to precisely coordinate T6SS expression, which is necessary to outcompete foes and colonize plants, along with other important and equally energetically expensive processes to minimize energy costs and optimize fitness.…”

Section: Discussionmentioning

confidence: 99%

Transcriptional organization and regulation of the Pseudomonas putida K1 type VI secretion system gene cluster

et al. 2023

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The type VI secretion system (T6SS) is an antimicrobial molecular weapon that is widespread in Proteobacteria and offers competitive advantages to T6SS-positive micro-organisms. Three T6SSs have recently been described in Pseudomonas putida KT2440 and it has been shown that one, K1-T6SS, is used to outcompete a wide range of phytopathogens, protecting plants from pathogen infections. Given the relevance of this system as a powerful and innovative mechanism of biological control, it is critical to understand the processes that govern its expression. Here, we experimentally defined two transcriptional units in the K1-T6SS cluster. One encodes the structural components of the system and is transcribed from two adjacent promoters. The other encodes two hypothetical proteins, the tip of the system and the associated adapters, and effectors and cognate immunity proteins, and it is also transcribed from two adjacent promoters. The four identified promoters contain the typical features of σ 70 -dependent promoters. We have studied the expression of the system under different conditions and in a number of mutants lacking global regulators. P. putida K1-T6SS expression is induced in the stationary phase, but its transcription does not depend on the stationary σ factor RpoS. In fact, the expression of the system is indirectly repressed by RpoS. Furthermore, it is also repressed by RpoN and the transcriptional regulator FleQ, an enhancer-binding protein typically acting in conjunction with RpoN. Importantly, expression of the K1-T6SS gene cluster is positively regulated by the GacS–GacA two-component regulatory system (TCS) and repressed by the RetS sensor kinase, which inhibits this TCS. Our findings identified a complex regulatory network that governs T6SS expression in general and P. putida K1-T6SS in particular, with implications for controlling and manipulating a bacterial agent that is highly relevant in biological control.

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Presence and absence of type VI secretion systems in bacteria

Cited by 28 publications

References 151 publications

Effectiveness ofPseudomonas aeruginosatype VI secretion system relies on toxin potency and type IV pili-dependent interaction

Effectiveness ofPseudomonas aeruginosatype VI secretion system relies on toxin potency and type IV pili-dependent interaction

A Quorum Sensing-Regulated Type VI Secretion System Containing Multiple Nonredundant VgrG Proteins Is Required for Interbacterial Competition in Chromobacterium violaceum

Transcriptional organization and regulation of the Pseudomonas putida K1 type VI secretion system gene cluster

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