Growth inhibition of Escherichia coli strain 82/r by d-camphor

A temporary growth inhibition of Escherichia coli resulted from exposure to d-camphor at concentrations ranging from 650 to 1100 μg/ml. The duration and intensity of inhibition varied as a function of d-camphor dose. Bacteriostatic effects produced by 850 μg/ml were non-selective and included a suspension of cell division, an increase in cell size, and a simultaneous suspension of DNA, RNA, and protein biosyntheses. These effects were in evidence 10 min after the addition of d-camphor and persisted for one and a half to two generations. Volatilization of d-camphor during and subsequent to this period of growth inhibition was negligible. d-Camphor reduced the surface tension of the culture medium from 74 to 58 dyn/cm. However, leakage of intracellular contents, as assayed by absorbance at 260 nm, was not observed in d-camphor inhibited cells. Furthermore, lowering the surface tension to 58 dyn/cm with Tween-80 failed to inhibit growth. No other physical changes were observed in d-camphor containing growth medium which would account for growth inhibition. The simultaneous suspension of DNA, RNA, and protein biosyntheses suggests that d-camphor interferes with a basic metabolic function upon which all these biosynthetic processes depend.