Effect of osmotic variation on the outer membrane proteins of Vibrio vulnificus: identification of a major heat-modifiable protein.

Cells of the moderately halophilic bacterium Vibrio vulnificus showed marked morphological changes, manifested primarily by pronounced cell elongation when grown in a defined medium with increased salt concentrations of 0.5 to 2.0%. These morphological changes were not accompanied by changes in outer membrane proteins (Omp). A similar lack of Omp variation was observed when cells were grown in heart infusion broth containing 1-2% NaCl. Osmotic upshock during growth also had no effect on Omp profiles. A heat modifiable protein with a molecular weight of 38 kD similar to Omp A of Escherichia coli, was identified in cells grown in heart infusion broth. The results suggest that under these osmotic conditions V. vulnificus may not need to regulate transport through modification of its outer membrane proteins.