Role for glycine betaine transport in Vibrio cholerae osmoadaptation and biofilm formation within microbial communities.

Vibrio cholerae is a halophilic facultative human pathogen found in marine and estuarine environments. Accumulation of compatible solutes is important for growth of V. cholerae at NaCl concentrations greater than 250 mM. We have identified and characterized two compatible solute transporters, OpuD and PutP, that are involved in uptake of glycine betaine and proline by V. cholerae. V. cholerae does not, however, possess the bet genes, suggesting that it is unable to synthesize glycine betaine. In contrast, many Vibrio species are able to synthesize glycine betaine from choline. It has been shown that many bacteria not only synthesize but also secrete glycine betaine. We hypothesized that sharing of compatible solutes might be a mechanism for cooperativity in microbial communities. In fact, we have demonstrated that, in high-osmolarity medium, V. cholerae growth and biofilm development are enhanced by supplementation with either glycine betaine or spent media from other bacterial species. Thus, we propose that compatible solutes provided by other microorganisms may contribute to survival of V. cholerae in the marine environment through facilitation of osmoadaptation and biofilm development.