Integrating signals to drive type VI secretion system killing

Bernal, Patricia; Murillo‐Torres, Marina; Allsopp, Luke P.

doi:10.1111/1462-2920.15255

Cited by 4 publications

(3 citation statements)

References 28 publications

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“…As an alternative approach, the authors searched the T6SS2 gene cluster for a bacterial enhancer binding protein (bEBP), which is the type of transcription factor that is essential to initiate σ 54 -dependent transcription. In its active form, a bEBP overcomes the inhibition of open complex formation initially imposed by σ 54 following recruitment of RNA polymerase (RNAP) to a σ 54 -dependent promoter [108,111,112]. Typically, bEBPs bind to enhancer sequences upstream of σ 54 -dependent promoters, form hexamers that facilitate ATPase activity, and interact directly with σ 54 -RNAP-promoter complexes to facilitate transcription.…”

Section: Regulatory Mechanisms Controlling T6ss Expressionmentioning

confidence: 99%

The type-VI secretion system of the beneficial symbiont Vibrio fischeri

Guckes

Miyashiro

2023

Microbiology

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The mutualistic symbiosis between the Hawaiian bobtail squid Euprymna scolopes and the marine bacterium Vibrio fischeri is a powerful experimental system for determining how intercellular interactions impact animal–bacterial associations. In nature, this symbiosis features multiple strains of V. fischeri within each adult animal, which indicates that different strains initially colonize each squid. Various studies have demonstrated that certain strains of V. fischeri possess a type-VI secretion system (T6SS), which can inhibit other strains from establishing symbiosis within the same host habitat. The T6SS is a bacterial melee weapon that enables a cell to kill adjacent cells by translocating toxic effectors via a lancet-like apparatus. This review describes the progress that has been made in understanding the factors that govern the structure and expression of the T6SS in V. fischeri and its effect on the symbiosis.

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Section: Regulatory Mechanisms Controlling T6ss Expressionmentioning

confidence: 99%

The type-VI secretion system of the beneficial symbiont Vibrio fischeri

Guckes

Miyashiro

2023

Microbiology

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“…How is the signal transferred to trigger sheath collapse? The regulation of T6SS in bacteria at multiple levels, including transcriptional, post-transcriptional and post-translational control is also an area of expanding research [59, 125, 170, 177–182]. As mentioned earlier, post-translational regulation of T6SSs enables a rapid transition from inactive proteins to assemble T6SSs; these regulatory components are likely widespread, warranting further investigations in the future.…”

Section: Future Perspectives and Conclusionmentioning

confidence: 99%

Killing in the name of: T6SS structure and effector diversity

Allsopp

Bernal

2023

Microbiology

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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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“…The activity of the T6SSs is tightly regulated at each possible stage, from transcriptional to translational and post-translational levels. It is common to find genes that encode T6SS regulatory elements within the T6SS clusters, with the most common elements being PpkA/PppA serine-threonine kinase/phosphatase systems, bacterial enhancer-binding proteins (bEBPs) and other regulators, such as TagF and forkhead-associated (FHA) domain-containing proteins [14][15][16][17][18]. For example, the P. aeruginosa H1-T6SS cluster encodes seven different regulatory components, including tagF1, pppA, ppkA and tagQRST [19][20][21] (Fig.…”

Section: Introductionmentioning

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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Integrating signals to drive type VI secretion system killing

Cited by 4 publications

References 28 publications

The type-VI secretion system of the beneficial symbiont Vibrio fischeri

The type-VI secretion system of the beneficial symbiont Vibrio fischeri

Killing in the name of: T6SS structure and effector diversity

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

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