PutA Is Required for Virulence and Regulated by PruR in .

, a Gram-negative opportunistic pathogenic bacterium, causes acute and chronic infections. Upon entering the host, alters global gene expression to adapt to host environment and avoid clearance by the host immune system. Proline utilization A (PutA) is a bifunctional enzyme, which converts proline to glutamate. Here we report that PutA was required for the virulence of in a murine acute pneumonia model. A mutant was more susceptible to oxidative stress compared to the wild type strain. An AraC/XylS family protein, PruR, directly bound to the upstream of -35 box in the promoter and activated expression. High concentration of proline in bacteria up-regulated expression, which led to the activation of expression. As a feedback regulation, glutamate produced by PutA released PruR from the promoter and turned off the expression. PruR affected bacterial virulence through the regulation of the expression. Altogether, these data are the first to reveal that PutA plays an important role in the pathogenesis of , as well as to describe the genetic regulation of PutA in .