Identification of the chromosomal YefM-YoeB toxin-antitoxin system in Vibrio parahemolyticus

Abstract:

[Background] Vibrio parahemolyticus is an important food-borne pathogen causing severe threats to public health. Toxin-antitoxin (TA) systems are widely distributed in the genomes of bacteria and archaea, and possess important biological functions. [Objective] To identify novel TA systems in V. parahemolyticus, and lay the foundation for exploring the underlying mechanism of bacterial pathogenicity and drug resistance from the aspect of TA systems. [Methods] The putative chromosomal type II TA systems in V. parahemolyticus were predicted by a web-based tool. The toxic effects of the putative toxins on Escherichia coli and the antitoxic effects of the corresponding antitoxins were assessed by growth curves analyses and spot dilution assays. Reverse transcription PCR was used to determine whether the genes encoding the toxin and antitoxin were co-transcribed. The homologous proteins of the newly identified TA system were determined by bioinformatics analysis. The regulation of their own promoters by the antitoxin and antitoxin-toxin complex was detected by LacZ reporter assay. [Results] Six putative chromosomal TA systems were identified in V. parahemolyticus. The product of the vp1820 gene (VP1820) had bactericidal activity against E. coli, which could be counteracted by the product of the vp1821 gene (VP1821). The genes vp1821 and vp1820 are co-transcribed. The vp1821-vp1820 locus encodes the YefM-YoeB TA system. The YefM antitoxin positively regulates the promoter, while the YefM-YoeB complex negatively regulates the promoter. [Conclusion] This study identifies a novel type II TA system in V. parahemolyticus, namely YefM-YoeB, and lays the foundation for further research on the role of this system in the pathogenicity and drug resistance of V. parahemolyticus.