The effect of 2,4-dichlorophenol on growth and plasmidic beta-lactamase activity in Escherichia coli

The toxic effects of 2,4-dichlorophenol on two strains of Escherichia coli harbouring plasmids with beta-lactamase activity were studied. The toxicant had a significant effect on growth at concentrations of 12 micrograms ml-1 for the JA 221 (pBR322) strain, as well as at 24 micrograms ml-1 for the J5-3 (RP4) strain. beta-Lactamase production was affected at concentrations of 96 micrograms ml-1 in both strains. However, beta-lactamase production does not seem to constitute a reliable toxicity test in view of its variability and relatively low sensitivity.