scholarly journals Horizontal Gene Transfer of Functional Type VI Killing Genes by Natural Transformation

2017 ◽  
Author(s):  
Jacob Thomas ◽  
Samit S. Watve ◽  
William C. Ratcliff ◽  
Brian K. Hammer
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Horizontal Transfer ◽  
Direct Injection ◽  
Spatially Explicit ◽  
Type Vi Secretion System ◽  
Effector Genes ◽  
Type Vi Secretion ◽  
A Cell ◽  
Explicit Simulation

AbstractHorizontal gene transfer can have profound effects on bacterial evolution by allowing individuals to rapidly acquire adaptive traits that shape their strategies for competition. One strategy for intermicrobial antagonism often used by Proteobacteria is the genetically-encoded contact-dependent Type VI secretion system (T6SS); a weapon used to kill heteroclonal neighbors by direct injection of toxic effectors. Here, we experimentally demonstrate thatVibrio choleraecan acquire new T6SS effector genes via horizontal transfer and utilize them to kill neighboring cells. Replacement of one or more parental alleles with novel effectors allows the recombinant strain to dramatically outcompete its parent. Through spatially-explicit simulation modeling, we show that the HGT is risky: transformation brings a cell into conflict with its former clonemates, but can be adaptive when superior T6SS alleles are acquired. More generally, we find that these costs and benefits are not symmetric, and that high rates of HGT can act as hedge against competitors with unpredictable T6SS efficacy. We conclude that antagonism and horizontal transfer drive successive rounds of weapons-optimization and selective sweeps, dynamically shaping the composition of microbial communities.

The type VI secretion system ofVibrio choleraefosters horizontal gene transfer

Science ◽  
2015 ◽  
Vol 347 (6217) ◽  
pp. 63-67 ◽  
Author(s):  
Sandrine Borgeaud ◽  
Lisa C. Metzger ◽  
Tiziana Scrignari ◽  
Melanie Blokesch
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Positive Control ◽  
Secretion System ◽  
Type Vi Secretion System ◽  
Natural Competence ◽  
Type Vi Secretion ◽  
Encoding Gene

Natural competence for transformation is a common mode of horizontal gene transfer and contributes to bacterial evolution. Transformation occurs through the uptake of external DNA and its integration into the genome. Here we show that the type VI secretion system (T6SS), which serves as a predatory killing device, is part of the competence regulon in the naturally transformable pathogenVibrio cholerae. The T6SS-encoding gene cluster is under the positive control of the competence regulators TfoX and QstR and is induced by growth on chitinous surfaces. Live-cell imaging revealed that deliberate killing of nonimmune cells via competence-mediated induction of T6SS releases DNA and makes it accessible for horizontal gene transfer inV. cholerae.

scholarly journals Vibrio cholerae Type VI Secretion System Auxiliary Cluster 3 is a Pandemic-associated Mobile Genetic Element

2019 ◽  
Author(s):  
Francis J. Santoriello ◽  
Lina Michel ◽  
Daniel Unterweger ◽  
Stefan Pukatzki
Keyword(s):  
Vibrio Cholerae ◽  
Horizontal Transfer ◽  
Mobile Genetic Element ◽  
Genomic Analysis ◽  
Secretion System ◽  
Specific Factor ◽  
Genetic Element ◽  
Type Vi Secretion System ◽  
Site Specific ◽  
Type Vi Secretion

AbstractAll sequenced Vibrio cholerae isolates encode a contact-dependent type VI secretion system (T6SS) in three loci that terminate in a toxic effector and cognate immunity protein (E/I) pair, allowing for competitor killing and clonal expansion in aquatic environments and the host gut. Recent studies have demonstrated variability in the toxic effectors produced by different V. cholerae strains and the propensity for effector genes to undergo horizontal gene transfer. Here we demonstrate that a fourth cluster, auxiliary cluster 3 (Aux3), encoding the E/I pair tseH/tsiH, is located directly downstream from two putative recombinases and is flanked by repeat elements resembling att sites. Genomic analysis of 749 V. cholerae isolates, including both pandemic and environmental strains, revealed that Aux3 exists in two states: a ∼40 kb prophage-like element in nine environmental isolates and a ∼6 kb element in pandemic isolates. These findings indicate that Aux3 in pandemic V. cholerae is evolutionarily related to an environmental prophage-like element. In both states, Aux3 excises from the chromosome via site-specific recombination to form a circular product, likely priming the module for horizontal transfer. Finally, we show that Aux3 can integrate into the Aux3-naïve chromosome in an integrase-dependent, site-specific manner. This highlights the potential of Aux3 to undergo horizontal transfer by a phage-like mechanism, which based on pandemic coincidence may confer currently unknown fitness advantages to the recipient V. cholerae cell.Significance StatementV. cholerae is a human pathogen that causes pandemics affecting 2.8 million people annually (1). The O1 El Tor lineage is responsible for the current pandemic. A subset of non-O1 strains cause cholera-like disease by producing the major virulence factors cholera toxin and toxin co-regulated pilus but fail to cause pandemics. The full set of V. cholerae pandemic factors is unknown. Here we describe the type VI secretion system (T6SS) Aux3 element as a largely pandemic-specific factor that is evolutionarily related to an environmental prophage-like element circulating in non-pathogenic strains. These findings shed light on V. cholerae T6SS evolution and indicate the Aux3 element as a pandemic-enriched mobile genetic element.

scholarly journals How environment shapes horizontal gene transfer

2020 ◽  
Vol 2 (7A) ◽  
Author(s):  
Rama Bhatia ◽  
Hande Kirit ◽  
Jonathan Bollback
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Gene Dosage ◽  
Recipient Cell ◽  
Endogenous Gene ◽  
Fitness Effects ◽  
Serovar Typhimurium ◽  
A Cell ◽  
Evolutionary Fate

The evolutionary fate of a horizontal gene transfer (HGT) event is determined by its fitness on the recipient cell, i.e., whether it is beneficial, neutral or deleterious. The distribution of fitness effects (DFE), thus is a fundamental predictor of the outcome of an HGT event. The environment plays a considerable role in determining the fitness cost of a horizontally transferred gene. We have studied the fitness effects of genes transferred from Salmonella enterica serovar Typhimurium to Escherichia coli in six environments, that potentially represent the conditions experienced by the two species. The data suggests high variability of genes in different environments. Genes, whose fitness varies substantially between environments, may be able to persist in populations while being deleterious in one environment, they may be neutral or even beneficial in another environment, suggesting that environmental fluctuations may increase the likelihood of HGT. In addition to the in vitro environments, we are also looking at, how changes in the intrinsic environment of a cell, after an HGT event, could affect fitness. An increase in protein dosage due to functional similarity of the horizontally transferred gene to the endogenous gene can cause an imbalance in the cell, thereby leading to a negative fitness effect. By comparing the growth rates of each ortholog gene with the wild type strain, we can elucidate when gene dosage acts as a barrier to HGT.

scholarly journals Investigation of the diversity of effector genes in the banana pathogen, Fusarium oxysporum f. sp. cubense , reveals evidence of horizontal gene transfer

2017 ◽  
Vol 19 (5) ◽  
pp. 1155-1171 ◽  
Author(s):  
Elizabeth Czislowski ◽  
Sam Fraser-Smith ◽  
Manuel Zander ◽  
Wayne T. O'Neill ◽  
Rachel A. Meldrum ◽  
...  
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Fusarium Oxysporum ◽  
Effector Genes
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