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Type 6 secretion system-mediated immunity to type 4 secretion system-mediated gene transfer.

ABSTRACT: Gram-negative bacteria use the type VI secretion system (T6SS) to translocate toxic effector proteins into adjacent cells. The Pseudomonas aeruginosa H1-locus T6SS assembles in response to exogenous T6SS attack by other bacteria. We found that this lethal T6SS counterattack also occurs in response to the mating pair formation (Mpf) system encoded by broad-host-range IncP? conjugative plasmid RP4 present in adjacent donor cells. This T6SS response was eliminated by disruption of Mpf structural genes but not components required only for DNA transfer. Because T6SS activity was also strongly induced by membrane-disrupting natural product polymyxin B, we conclude that RP4 induces "donor-directed T6SS attacks" at sites corresponding to Mpf-mediated membrane perturbations in recipient P. aeruginosa cells to potentially block acquisition of parasitic foreign DNA.

SUBMITTER: Ho BT

PROVIDER: S-EPMC4034461 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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Type 6 secretion system-mediated immunity to type 4 secretion system-mediated gene transfer.

Ho Brian T BT Basler Marek M Mekalanos John J JJ

Science (New York, N.Y.) 20131001 6155

Gram-negative bacteria use the type VI secretion system (T6SS) to translocate toxic effector proteins into adjacent cells. The Pseudomonas aeruginosa H1-locus T6SS assembles in response to exogenous T6SS attack by other bacteria. We found that this lethal T6SS counterattack also occurs in response to the mating pair formation (Mpf) system encoded by broad-host-range IncPα conjugative plasmid RP4 present in adjacent donor cells. This T6SS response was eliminated by disruption of Mpf structural ge ...[more]

PMID: 24115441

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Project description:Porphyromonas gingivalis is one of the major bacteria that causes periodontitis. Chronic periodontitis is a severe form of periodontal disease that ultimately leads to tooth loss. Virulence factors that contribute to periodontitis are secreted by Type IX Secretion System (T9SS). There are aspects of T9SS protein components that have yet to be characterised. Thus, the aim of this study is to investigate the phylogenetic relationship between members of 20 T9SS component protein families. The Bayesian Inference (BI) trees for 19 T9SS protein components exhibit monophyletic clades for all major classes under Bacteroidetes with strong support for the monophyletic clades or its subclades that is consistent with phylogeny exhibited by the constructed BI tree of 16S rRNA. The BI tree of PorR is different from the 19 BI trees of T9SS protein components as it does not exhibit monophyletic clades for all major classes under Bacteroidetes. There is strong support for the phylogeny exhibited by the BI tree of PorR which deviates from the phylogeny based on 16S rRNA. Hence, it is possible that the porR gene is subjected to horizontal transfer as it is known that virulence factor genes could be horizontally transferred. Seven genes (porR included) that are involved in the biosynthesis of A-LPS are found to be flanked by insertion sequences (IS5 family transposons). Therefore, the intervening DNA segment that contains the porR gene might be transposed and subjected to conjugative transfer. Thus, the seven genes can be co-transferred via horizontal gene transfer. The BI tree of UgdA does not exhibit monophyletic clades for all major classes under Bacteroidetes which is similar to the BI tree of PorR (both are a part of the seven genes). Both BI trees also exhibit similar topology as the four identified clusters with strong support and have similar relative positions to each other in both BI trees. This reinforces the possibility that porR and the other six genes might be horizontally transferred. Other than the BI tree of PorR, the 19 other BI trees of T9SS protein components also exhibit evidence of horizontal gene transfer. However, their genes might undergo horizontal gene transfer less frequently compared to porR because the intervening DNA segment that contains porR is easily exchanged between bacteria under Bacteroidetes due to the presence of insertion sequences (IS5 family transposons) that flank it. In conclusion, this study can provide a better understanding about the phylogeny of T9SS protein components.

Dataset Information

Type 6 secretion system-mediated immunity to type 4 secretion system-mediated gene transfer.

Publications

Type 6 secretion system-mediated immunity to type 4 secretion system-mediated gene transfer.

Similar Datasets

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