ACID SENSITIVITY INDUCTION (ASI) AT ALKALINE PH IN ESCHERICHIA-COLI INVOLVES 2 MAJOR SENSITIZATION COMPONENTS, INDUCTION OF BOTH BEING SWITCHED ON BY INCREASED INTERNAL PH

Acid sensitivity induction (ASI) at alkaline pH in Escherichia coli 11 57 (phoE) is only fully mounted if protein synthesis occurs for the fi rst 5 min of the 12-15 min induction period, but appreciable sensitiza tion occurs in the presence of chloramphenicol indicating that there a re protein synthesis-independent and -dependent components (components 1 and 2). Component 1 sensitization is in place after 10 min at pH(o) 9.0 but the dependent process is induced slightly more slowly. Collap sing Delta pH at pH(o) 9.0 did not prevent full ASI, indicating that c omponent 1 and 2 induction does not depend on increased Delta pH. The two induction (or activation) processes responded differently to inter mediate levels of external alkalinization; component 1 was induced at pH(o) 8.3 but component 2 needed pH(o) 8.4 or greater. Collapsing Delt a pH at pH(o) 8.0 led to full induction of component 1 and appreciable induction of component 2, indicating that both processes are triggere d if pH(i) rises to 8.0 or greater (presumably at pH(o) 8.3-8.4). Comp onent 1 appears less important for ASI in 1157-4(phoE(+)) than in 1157 (phoE).