Temperature-sensitive, colicin M-tolerant mutant of Escherichia coli

Abstract

A mutant sensitive to colicin M at 30 degrees C and tolerant at 42 degrees C to high concentrations of colicin M was isolated from Escherichia coli K-12. A temperature shift from 30 to 42 degrees C rescued all cells up to the time they started to lyse at 30 degrees C (25 min after addition of colicin M). The growth rate at 42 degrees C remained unaffected by colicin M. AT 42 degrees C the cell-bound colicin M was inactivated by trypsin, sodium dodecyl sulfate, and antiserum against colicin M. Ferrichrome competed with colicin M at 42 degrees C only during the initial adsorption to the common receptor protein in the outer membrane. Since cells lysed earlier at 30 degrees C when they had been preincubated with colicin M at 42 degrees C, we conclude that the process leading finally to cell lysis is initiated at 42 degrees C and stops at a later stage of colicin M trypsin, dodecyl sulfate, and antiserum when cells were transferred from 30 to 42 degrees C, we assume that colicin M is translocated from its target site towards the cell surface. The mutation conferring tolerance was mapped close to the rpsL gene.