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.