The non-motile phenotype of <it>Salmonella hha ydgT </it>mutants is mediated through PefI-SrgD

• Main Authors: Coombes Brian K, Bysice Andrew M, Wallar Lauren E
• Format: Article
• Language: English
• Published: BMC 2011-06-01
• Series: BMC Microbiology
• Online Access: http://www.biomedcentral.com/1471-2180/11/141

<p>Abstract</p> <p>Background</p> <p>Two ancestral nucleoid-associated proteins called Hha and YdgT contribute to the negative regulation of several virulence-associated genes in <it>Salmonella enterica </it>serovar Typhimurium. Our previous work showed that Hha and YdgT proteins are required for negative regulation of <it>Salmonella </it>Pathogenicity Island-2 and that <it>hha ydgT </it>double mutants are attenuated for murine infection. Interestingly, <it>hha ydgT </it>mutant bacteria exhibited a non-motile phenotype suggesting that Hha and YdgT have a role in flagellar regulation.</p> <p>Results</p> <p>In this study we show that the non-motile phenotype of <it>hha ydgT </it>mutants 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 acquired <it>pefI-srgD </it>region was found to be partially responsible for this phenotype since deletion of <it>pefI-srgD </it>in a <it>hha ydgT </it>deletion background resulted in transient restoration of class II/III and III transcription, expression of surface flagella, and motility in the quadruple mutant.</p> <p>Conclusion</p> <p>These data extend our current understanding of the mechanisms through which Hha and YdgT regulate flagellar biosynthesis and further describe how <it>S</it>. Typhimurium has integrated horizontal gene acquisitions into ancestral regulatory networks.</p>