HETEROLOGOUS EXPRESSION OF ESCHERICHIA-COLI PORIN GENES IN SALMONELLA-TYPHI TY2 - REGULATION BY MEDIUM OSMOLARITY, TEMPERATURE AND OXYGEN AVAILABILITY

Electrophoretic analysis of outer membrane proteins showed that Salmon ella typhi OmpC expression is not reciprocally regulated relative to O mpF as described for Escherichia coli and S. typhimurium. When bacteri a were grown in minimal media, both OmpC and OmpF were repressed as th e osmolarity increased. However, in Luria broth, expression of OmpC wa s slightly induced by osmolarity up to 0.3 osmM, Plasmids bearing E. c oli ompC-lacZ or ompF-lacZ gene fusions were studied for their express ion in S. typhi and E. coli. Under anaerobic growth conditions, expres sion of ompC-lacZ in S. typhi was maximal at 0.16 osmM, while in E. co li expression was maximal at 0.7 osmM. ompF-lacZ expression was simila rly repressed by medium osmolarity and anaerobiosis in both species. I n contrast, a drastic difference in the regulation of OmpF by temperat ure was observed; at 37 degrees C ompF-lacZ expression was repressed i n E. coli, while in S. typhi it was induced.