Conversion of cis unsaturated fatty acids to trans, a possible mechanism for the protection of phenol-degrading Pseudomonas putida P8 from substrate toxicity

Abstract

A trans unsaturated fatty acid was found as a major constituent in the lipids of Pseudomonas putida P8. The fatty acid was identified as 9-trans-hexadecenoic acid by gas chromatography, argentation thin-layer chromatography, and infrared absorption spectrometry. Growing cells of P. putida P8 reacted to the presence of sublethal concentrations of phenol in the medium with changes in the fatty acid composition of the lipids, thereby increasing the degree of saturation. At phenol concentrations which completely inhibited the growth of P. putida, the cells were still able to increase the content of the trans unsaturated fatty acid and simultaneously to decrease the proportion of the corresponding 9-cis-hexadecenoic acid. This conversion of fatty acids was also induced by 4-chlorophenol in nongrowing cells in which the de novo synthesis of lipids had stopped, as shown by incorporation experiments with labeled acetate. The isomerization of the double bond in the presence of chloramphenicol indicates a constitutively operating enzyme system. The cis-to-trans modification of the fatty acids studied here apparently is a new way of adapting the membrane fluidity to the presence of phenols, thereby compensating for the elevation of membrane permeability induced by these toxic substances.

Bacterial diversity promotes community stability and functional resilience after perturbation

“…Benzene addition also resulted in large decreases in bacterial and DNA concentrations but, in contrast to copper treatment, led to larger shifts in community structure. Benzene can be selectively toxic as its main effect is on cell membrane integrity, which may exert less effect on spore forming Gram-positive bacteria and Gram-negative species with cell membrane adaptations (Heipieper et al, 1992;Gutierrez et al, 1999). The toxicity of benzene, and other aromatic hydrocarbons, is attributed to the partitioning of lipophilic compounds into the lipid bilayer of cell membranes, causing loss of integrity and dissipation of the proton motive force.…”

“…The toxicity of benzene, and other aromatic hydrocarbons, is attributed to the partitioning of lipophilic compounds into the lipid bilayer of cell membranes, causing loss of integrity and dissipation of the proton motive force. Bacteria may develop resistance by increasing the amount of saturated fatty acids present in their membrane (Keweloh et al, 1991;Gutierrez et al, 1999) and conversion from the cis-to the transconfiguration of unsaturated fatty acids has been observed for strains of Pseudomonas putida exposed to organic solvents (Heipieper et al, 1992;Weber et al, 1994). Saturated and trans fatty acids show a higher degree of ordering and therefore increased surface density, which is believed to oppose the partitioning of lipophilic solutes into the lipid bilayer (Marqusee and Dill, 1986).…”

Long‐term in vitro treatment of INS‐1 rat pancreatic β‐cells by unsaturated free fatty acids protects cells against gluco‐ and lipotoxicities via activation of GPR40 receptors

“…28 The more double bonds in the chain structure formed in the cis configuration in the FFA, the less flexibility and cytotoxicity the FFA will exhibit. 29 According to this theory, the cytotoxicity of the FFAs evaluated in the present study should be PA > OA> LA > a-LA. In the present study, PA markedly impaired INS-1 cell viability and function compared with the unsaturated FFAs.…”

Transcriptional control of the main aromatic hydrocarbon efflux pump in Pseudomonas

“…Aromatic hydrocarbon-tolerant P. putida strains use several mechanisms to resist high solvent concentrations (Ramos et al, 2002;Santos et al, 2004;Roma-Rodrigues et al, 2010). The first resistance system takes place at the membrane; contact with solvents induces membrane alterations (Heipieper et al, 1992;Pinkart et al, 1996). A common mechanism to all P. putida strains is the isomerization of cis-unsaturated fatty acids into the corresponding trans isomers, which allow a denser packing of the membranes (Sikkema et al, 1995).…”

“…For this the cells use different strategies. In one short-term response cis unsaturated fatty acids are isomerized to trans unsaturated fatty acids, a reaction, mediated by a cis-trans isomerase called CTI (Heipieper et al, 1992;Junker and Ramos, 1999). This results in cells with denser membranes which is a selective advantage that allows cells to adapt immediately to the new environmental conditions.…”