Abstract
The role of two chaperone proteins, DnaK and the cooperating factor DnaJ, in
Escherichia coli
antibiotic susceptibility to three antibiotics (a β-lactam, chloramphenicol, tetracycline) has been
studied. It was found that null
dnaJ
and
dnaKdnaJ
mutants are impaired in the functions leading to antibiotic susceptibility. The secretion of β-lactamase to the periplasmic space is
diminished in both mutants, and the additive effect of the two mutations was observed. The activity of chloramphenicol acetyltransferase is also impaired in an additive manner in both mutant strains. Tetracycline
uptake is changed only in the double deletion mutant. These defects were observed only during incubation at high temperature (42°C). Efficient complementation of some of these defects by the wild-type
alleles introduced on low-copy number plasmid was achieved. Minimal inhibitory concentrations and the titer of the wild-type strains,
ΔdnaJ
and
ΔdnaKdnaJ
mutants treated with ampicillin,
chloramphenicol, and tetracycline were also determined. Higher susceptibility of both mutants to chloramphenicol and tetracycline, as compared to their wild-type parent, was observed only after 1 h preincubation
of cultures at 42°C. On the contrary, both mutants were less susceptible to ampicillin than their parent strain.