INFLUENCE OF CULTURE CONDITIONS ON EXPRESSION OF THE 40-KILODALTON PORIN PROTEIN OF VIBRIO-ANGUILLARUM SEROTYPE O2

Vibrio anguillarum serotype O2 strains express a 40-kDa outer membrane porin protein. Immunoblot analysis revealed that antigenic determinan ts of the V. anguillarum O2 40-kDa porin were conserved within bacteri al species of the genus Vibrio. The relative amounts of the V. anguill arum O2 40-kDa porin were enhanced by growth of V. anguillarum O2 in C M9 medium containing 5 to 10% sucrose or 0.1 to 0.5 M NaCl. In contras t, the levels of the porin were significantly reduced when cells were grown at 37 degrees C, and a novel 60-kDa protein was also observed. H owever, the osmolarity or ionic concentration of the growth medium did not influence expression of the 60-kDa protein. Growth in medium cont aining greater than 0.6 mM EDTA reduced production of the V. anguillar um O2 40-kDa porin and enhanced levels of a novel 19-kDa protein. Thus , expression of the V. anguillarum O2 40-kDa porin was osmoregulated a nd possibly coregulated by temperature. The N-terminal amino acid sequ ence of the V. anguillarum O2 40-kDa protein and the effect of environ mental factors on the cellular levels of the porin suggested that the V. anguillarum O2 40-kDa porin was functionally similar to the OmpC po rin of Escherichia coli. However, pore conductance assays revealed tha t the V. anguillarum O2 40-kDa porin was a general diffusion porin mid a pore size in the range of that of the OmpF porin of E. coli.