[Lethality of the dnaB thermosensitive mutation of E. coli : comparison with thymine-less death]

In a dnaB thermosensitive mutant of the bacterium E. coli, a shift to non-permissive conditions leads to the immediate cessation of DNA synthesis and results in a sizable loss of viability. Under conditions where protein synthesis is inhibited, either by addition of antibiotics (chloramphenicol, rifampicin) or by amino-acids starvation, there is a marked increase in viability. This is reminiscent of the behavior of thymine-deprived bacteria and suggests that both types of death, induced by a block in the displacement of the DNA-replicative fork, follow the same pattern.