Suitability of the trans/cis ratio of unsaturated fatty acids in Pseudomonas putida NCTC 10936 as an indicator of the acute toxicity of chemicals

This study explored the suitability of using the trans/cis ratio of unsatur ated fatty acids as an indicator of the acute toxicity of membrane active h azardous chemicals. The conversion of cis into trans fatty acids in Pseudom onas putida NCTC 10936 in response to 4-chlorophenol and temperature change s was compared with the results from another kind of toxicity test using th e same organism, based on the sensitivity of its xylose oxidation-driven AT P synthesis to uncoupling. The response of both indicators is believed to b e largely due to changes in the fluidity of the cytoplasmic membrane. Howev er, the electron transport phosphorylation reacted faster and more sensitiv ely to the fluidizing effect of 4-chlorophenol than the isomerization of un saturated fatty acids. Therefore, measuring the trans/cis ratio does not pr ovide as good early warning signals of acute toxicity as monitoring the res ponse of the electron transport phosphorylation. If used as an indicator of chemostress, with Pseudomonas species as test organisms, the ratio should only be used in conjunction with other parameters reflecting the energetic state of the cells. (C) 2001 Academic Press.