The non-motile phenotype of Salmonella hha ydgT mutants is mediated through PefI-SrgD

AbstractBackgroundTwo ancestral nucleoid-associated proteins called Hha and YdgT contribute to the negative regulation of several virulence-associated genes inSalmonella entericaserovar Typhimurium. Our previous work showed that Hha and YdgT proteins are required for negative regulation ofSalmonellaPathogenicity Island-2 and thathha ydgTdouble mutants are attenuated for murine infection. Interestingly,hha ydgTmutant bacteria exhibited a non-motile phenotype suggesting that Hha and YdgT have a role in flagellar regulation.ResultsIn this study we show that the non-motile phenotype ofhha ydgTmutants is due to decreased levels of the master transcriptional regulator FlhD4C2resulting in down-regulation of class II/III and class III flagellar promoters and lack of surface flagella on these cells. The horizontally acquiredpefI-srgDregion was found to be partially responsible for this phenotype since deletion ofpefI-srgDin ahha ydgTdeletion background resulted in transient restoration of class II/III and III transcription, expression of surface flagella, and motility in the quadruple mutant.ConclusionThese data extend our current understanding of the mechanisms through which Hha and YdgT regulate flagellar biosynthesis and further describe howS. Typhimurium has integrated horizontal gene acquisitions into ancestral regulatory networks.

The non-motile phenotype of Salmonella hha ydgT mutants is mediated through PefI-SrgD Journal Articles