ToxR of Vibrio cholerae affects biofilm, rugosity and survival with Acanthamoeba castellanii.

• Background: Vibrio cholerae causes the diarrheal disease cholera and utilizes different survival strategies in aquaticenvironments. V. cholerae can survive as free-living or in association with zooplankton and can build biofilm andrugose colonies. The bacterium expresses cholera toxin (CT) and toxin-coregulated pilus (TCP) as the mainvirulence factors. These factors are co-regulated by a transcriptional regulator ToxR, which modulates expression ofouter membrane proteins (OmpU) and (OmpT). The aims of this study were to disclose the role of ToxR inexpression of OmpU and OmpT, biofilm and rugose colony formation as well as in association with the free-livingamoeba Acanthamoeba castellanii at different temperatures. Results: The toxR mutant V. cholerae produced OmpT, significant biofilm and rugose colonies compared to thewild type that produced OmpU, decreased biofilm and did not form rugoes colonies at 30°C. Interestingly, neitherthe wild type nor toxR mutant strain could form rugose colonies in association with the amoebae. However, duringthe association with the amoebae it was observed that A. castellanii enhanced survival of V. cholerae wild typecompared to toxR mutant strain at 37°C. Conclusions: ToxR does seem to play some regulatory role in the OmpT/OmpU expression shift, the changes inbiofilm, rugosity

Nyckelord

V. cholerae

Outer membrane proteins

Rugose colonies

Biofilm

Association with amoebae

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