Fatty Acid Composition of Comamonas testosteroni under Hexachlorobenzene Loading Conditions

Abstract

Changes in the lipid composition in bacterial membranes are considered to be the most important adaptation mechanisms to adverse chemical factors. The aim of the study was to compare the hexachlorobenzene effects on the fatty acid composition of total lipids Comamonas testosteroni. Methods. The study was performed with C. testosteroni UCM B-400 and B-401, B-213 strains. Bacteria were grown in the Luria-Bertrani (LB) liquid medium containing 10 and 20 mg/L of hexachlorobenzene (HCB). After cultivation, the biomass was separated by centrifugation and the fatty acid composition of total lipids was determined through analyzing its methyl esters. To assess the cell membrane properties, such parameters as the lipid unsaturation index, the average carbon chain length of fatty acids, and the membrane viscosity index were determined. Results. In the fatty acids spectrum of C. testosteroni B-400 after cultivation in a medium containing 20 mg/L of HCB, the contents of unsaturated hexadecenoic (C16:1) and octadecenoic (C18:1) acids were lower by 10.6 and 5.5%, respectively, and that of saturated hexadecanoic (C16:0) acid was higher by 8.4%, compared to the control. The fatty acid composition of C. testosteroni B-401 was more stable compared to strain B-400. Collection strain C. testosteroni B-213 compared to strains isolated from soil with high HCB load, in the presence of 10 and 20 mg/L of HCB had the highest relative content of saturated hexadecanoic acid (C16:0) up to 38.33—40.7%. Unsaturated octadecenoic acid decreased at the doses 10 and 20 mg/L to 1.5—2% compared to the control. In all strains under the HCB impact, there was an increase in the relative content of C17-cyclopropanoic acid compared to control variants. Conclusions. C. testosteroni UCM B-400, B-401, and B-213 bacteria under cultivation conditions in HCB-containing medium, decreasing the degree of lipid unsaturation and increasing the relative content of C17-cyclopropanoic acid can be considered as the main mechanisms regulating the cytoplasmic membrane fluidity; the displaying of these protective reactions had a strain trait and did not depend on the adaptation in natural isolating places.