CadC regulates cad and tdc operons in response to gastrointestinal stresses and enhances intestinal colonization of Klebsiella pneumoniae (CBX106). unidentified

To explore the mechanisms enabling Klebsiella pneumoniae to survive in the gastrointestinal tract, we characterized the roles of the cad and tdc operons during the bacterial response to acid and bile stress. The NTUH-K2044 wild-type strain displayed an acid tolerance response to inorganic acid and was able to survive in bile encountered in vivo. To clarify the regulatory function of CadC in K. pneumoniae, the transcriptome analyses of the cadC mutant and the wild-type strain after acid adaptation were compared. Transcription of threonine dehydratase (tdcB) was more highly induced in the wild-type than in the cadC mutant strain. This result implied that the transcriptional regulation of the tdc locus might depend on CadC. Transcriptional regulation of the cad and tdc operons under either acid or bile stress was analyzed by real-time RT-PCR. Altered transcription of the cad and tdc operons by acid depended on CadC. Under either bile stress or acidic conditions, the transcriptional regulation of the tdc operon depended on TdcA.