SUMMARY:The effects of phenol and 2-phenoxyethanol on the oxygen uptake of washed suspensions and a disrupted cell' preparation of Escherichia coli, with different substrates, has been further investigated. Stimulation of oxygen uptake with mannitol or glucose as substrate was not due to an increase in the viable population or associated with an uncoupling effect. The results obtained with a disrupted cell preparation capable of oxidizing glucose and lactic acid to pyruvic acid, on comparison with results with intact organisms, suggest that enzyme location may account for the differences in inhibitory activity obtained with different substrates.Hugo & Street (1952) showed that the action of phenol and 2-phenoxyethanol (phenoxetol) on the course of oxygen uptake by washed suspensions of Escherichia coli differed markedly with different substrates. I n the presence of phenol (0.1-0.2 %, w/v; 0~010-0~021 M) and 2-phenoxyethanol (0-1-0-2 yo, w/v; 0.007-0.014~) a stimulation of the rate of oxygen uptake of the order of 10-20 yo occurred when glucose, mannitol or lactose was used as substrate; these same doses inhibited the rate of oxygen uptake by 10-15 Yo when succinate, lactate, pyruvate or acetate was the substrate. These results were difficult to explain on the hypothesis that these two antiseptics are non-specific protoplasmic poisons. Three working hypotheses were considered in an attempt to explain these effects of substrate on the response of oxygen uptake to the antiseptics: (i) that the differences reflect changes in the population of viable organisms : (ii) that the stimulations of oxygen uptake were associated with an uncoupling effect such as is shown by the nitrophenols; (iii) that the differences could be attributed to an effect of the antiseptic on permeability of the organisms to substrate, coupled with differences in the location of the enzymes involved in the oxidation of different substrates. The experiments now described were undertaken to evaluate these hypotheses.
METHODSChemicals. Diphosphopyridine nucleotide (DPN) and adenosine triphosphate (ATP) were samples supplied by Messrs L. Light and Co. Ltd.; the former when assayed by the method of Racker (1950) was found to contain 82 yo, w/w, DPN.Sugars and mannitol were of bacteriological grade as supplied by Messrs T. Kerfoot Ltd. The 2-phenoxyethanol was a sample which complied with the requirements of the British Pharmaceutical Codex. The methylene blue was a