Identification of determinants involved in temperature-dependent colony morphology in Vibrio cholerae co969

Adaptation to shifting temperatures is crucial for the survival of the bacterial pathogen Vibrio cholerae. Colony rugosity, a phenotype linked to biofilm, is regulated by temperature in some V. cholerae strains: the rugose colony-forming V. cholerae El Tor clinical isolate co969 formed smooth colonies when cultured below 22ºC.We performed a loss-of-function screen for potential biofilm repressors at low temperatures. By using random transposon-insertion mutagenesis on V. cholerae co969 and selecting mutants that inappropriately formed rugose colonies at 22ºC, we found BipA, a conserved ribosome-associated GTPase, that is critical for this temperature-dependent phenomenon. To filter out potential temperature-independent repressors, we performed a similar screen for rugose colonies at 37ºC using the temperature-insensitive smooth V. cholerae strain C6706. Finally, we did an additional screening for aberrantly smooth co969 colonies at 37ºC to identify new genes involved in biofilm formation.