Regulation of Biofilm Formation and Norspermidine Production by Iron in Vibrio Cholerae

Vibrio cholerae is a pathogenic bacterium and the causative agent of the diarrheal disease cholera. V. cholerae is thought to persist in the environment in the form of a biofilm. Biofilm formation is regulated by signals ranging from self produced signals to environmental signals. This work investigated whether iron availability and production of the polyamine, norspermidine, are linked to biofilm regulation. Through investigating mutants defective in vibriobactin synthesis (a siderophore) in regards to iron availability, I have shown that iron deficiency inhibits biofilm formation and that mutants defective in siderophore synthesis have increased biofilm formation compared to wild-type. Vibriobactin contains a norspermidine backbone and previous work has shown that norspermidine is a pro-biofilm signal. HPLC data does not show any increase in norspermidine levels in the cell or in the extracellular environment, but conditioned media experiments have shown that a pro-biofilm signal is present in the culture medium. Preliminary data suggests that a modified, potentially acetylated, form of norspermidine is the pro-biofilm signal in this system. Future work will be directed at acetylase mutants and media fractionation in order to conclusively determine what the pro-biofilm signal is in this system