Investigation of the induction of melanogenesis in Vibrio cholerae 569B

A melanin synthetic pathway in Vibrio Cholerae 569B was shown to function under certain physiological conditions. Osmotic stress in conjunction with increased temperature was the primary inducing condition. Acidic starting pH of the growth media and nutrient depletion at high temperatures were also shown to induce melanogenesis by lowering the tolerance of V. cholerae to salinity. Melanogenesis did not occur as the result of autooxidation of its intermediates via cell lysis or cell leakage. In addition, melanin inducive physiological conditions did not elevate the expression of two virulence determinants of V. cholerae, namely ompU and cholera toxin. Finally, melanogenesis was found to be ubiquitous among Vibrio strains other than 569B.