562015-03-24 , 法政大学大学院理工学・工学研究科
Vibrio cholerae，the etiological agent of cholera, shows chemotaxis, which has been implicated in pathogenicity. The bacterium has more than 40 homologs of methyl-accepting chemotaxis protein (MCP), named MCP-like protein (MLP). In this study, I aimed at understanding temperature-regulation of mlp. Based on the comprehensive Northern blotting analyses, the mlp genes were categorized into three groups: ‘23°C-specific’ (9 genes), ‘37°C-specific’ (8 genes) and ‘relatively temperature-insensitive’ (25 genes). The warm-induction of the mlp37 gene, encoding a chemoreceptor for taurine and various amino acids, was shown to occur at the level of transcription initiation. The expression of mlp37 from the foreign promoter abolished the temperature dependence of taurine response, suggesting that regulation of taurine taxis is mainly caused by regulation of the receptor expression. The mlp37 expression was negatively regulated by the transcriptional activator ToxR, required for cholera toxin gene expression, suggesting that taurine taxis is inversely correlated to toxin production. On the other hand, the cold-specific induction of mlp10 was shown to involve a post-transcriptional mechanism.These results suggest that V. cholerae senses temperature to modulate its repertoire of MLPs to cope with various environments where it has to sense different sets of stimuli.