THERMALLY-INDUCED CELL-LYSIS IN ESCHERICHIA-COLI K12

Escherichia coli cells exposed to high temperatures exhibit a progress ive loss of viability. We observed two mechanisms of cell death induce d by lethal temperatures: with and without lysis. The number of cells lysed by heat decreased at later stages of the growth curve, when cell s were pre-treated at lower temperatures for 10 minutes and when cells were pre-treated with novobiocin, nalidixic acid and cadmium chloride . Cell lysis was similar in wild type, rpoH, groE and dnaK mutant cell s as well as in cells which overproduce heat shock proteins GroE or Dn aK. Results using cells aligned for cell division and cells growing at 42 degrees C, 45 degrees C and 47 degrees C suggest that cells near d ivision are more sensitive to lysis and that a high concentration of h eat-shock proteins increases their resistance to lysis.