UNDER A-SALT: Investigating the role of CosR in Osmotic Stress Response Of Vibrio parahaemolyticus

Abstract

The marine bacterium Vibrio parahaemolyticus has evolved multiple strategies for adapting to short- and long-term shifts in osmolarity. One such mechanism involves the uptake and/or biosynthesis of small organic molecules known as compatible solutes. These compatible solutes act to balance the osmolarity of the cell without disrupting important biological processes. V. parahaemolyticus is able to uptake compatible solutes through six transport systems: two ABC type transporters named ProU1 and ProU2 and four betaine carnitine choline transporters (BCCTs). Additionally, V. parahaemolyticus can biosynthesize glycine betaine and ectoine. Ectoine gene expression was previously shown to be regulated by a MarR-type regulator CosR in V. cholerae. In this study, we identify a CosR homologue (VP1906) present in all strains of V. parahaemolyticus and characterize its role in the osmotic stress response through the generation of a cosR deletion strain. Through quantitative Real-Time PCR (qPCR), we demonstrate that CosR plays a role in regulation of the ectoine biosynthesis genes as well as bcct1 (VP0456) and bcct3 (VP1905). Additionally, we show that CosR is able to bind to the promoter regions of these operons, as well as directly repress transcription of the ectABCaspK operon in vitro. Taken together, these data suggest that CosR is an important global regulator in the osmotic stress response of V. parahaemolyticus.