Effect of Environmental Factors on the trans/cis Ratio of Unsaturated Fatty Acids in Pseudomonas putida S12

Abstract

The membrane reactions of Pseudomonas putida S12 to environmental stress were investigated. Cells reacted to the addition of six different heavy metals with an increase in the ratio of trans to cis unsaturated fatty acids. A correlation among the increase in the trans/cis ratio, the toxic effects of the heavy metals, and nonspecific permeabilization of the cytoplasmic membrane, as indicated by an efflux of potassium ions, was measured. Cells previously adapted to toxic concentrations of toluene exhibited increased tolerance to all applied concentrations of zinc compared with nonadapted cells. Cells exposed to different temperatures grew optimally at 30؇C. The degree of saturation of the membrane fatty acids of these cells decreased with decreasing temperature. An increase in the trans/cis ratio of unsaturated fatty acids took place only at higher temperatures. Osmotic stress, expressed as reduced water activity, was obtained by using different types of solutes. Only in the presence of toxic concentrations of sodium chloride or sucrose did the trans/cis ratio increase. At no applied water activity a significant effect of glycerol on the trans/cis ratio was measured. When cells were exposed to different pHs, a distinct optimum cis/trans isomerase activity was measured at pHs between 4.0 and 5.0, whereas at higher or lower pHs no reaction occurred. This optimum coincided with a loss of viability between pH 4 and 5.

Transcriptional regulation of fatty acid cis–trans isomerization in the solvent‐tolerant soil bacterium, Pseudomonas putida F1

“…The production of trans-UFA in P. putida during growth has been documented Heipieper et al, 1996). However, several studies reported that some P. putida strains produce trans-UFA only in stress or nongrowing conditions, such as during sample preparation (Härtig et al, 2005;Loffhagen et al, 2007).…”

“…P. putida is of particular interest in biotechnology because of its high potential in bioremediation and biodegradation processes (Loh and Cao, 2008;Samuel et al, 2014). Thus, several reports report that trans-UFA plays an important role in the adaptation of diverse P. putida strains to the increase in temperature, the presence of organic solvents and heavy metals, as well as osmotic stress and addition of membrane-active antibiotics (Heipieper et al, 1996;Isken et al, 1997;Neumann et al, 2003). It is generally accepted that cti is constitutively expressed in Pseudomonas spp.…”

Thecis–transisomerase of unsaturated fatty acids inPseudomonasandVibrio: biochemistry, molecular biology and physiological function of a unique stress adaptive mechanism

“…Such a model for the regulation of Cti activity also su⁄ciently explains the often reported relation between the degree of cis^trans isomerization and the toxicity caused by a certain concentration of an environmental stress factor [16,30]. As another result of the reaction catalyzed by the enzyme a reduction of membrane £uidity occurs and, as the enzyme cannot reach its target when membrane £uidity has reached its normal level the enzyme is forced out of the bilayer [45].…”

“…In summary, all membrane a¡ecting stimuli such as organic solvents, osmotic stress (caused by NaCl and sucrose), heavy metals, heat shock, and membrane-active antibiotics were shown to activate the system [11,30^32]. However, stress conditions, such as osmotic stress caused by glycerol, cold shock, and high pH, that are known not to be activators of cellular K þ -uptake^the ¢rst cellular reaction to membrane damage leading to increased perme-abilization^did not cause activation of Cti [30,31]. Such Concentrations which caused an increase in the trans/cis ratio of unsaturated fatty acids to 50% of the maximum trans/cis level reached at saturating concentrations of the toxin.…”

Complexity in efflux pump control: cross‐regulation by the paralogues TtgV and TtgT

“…The main passive mechanism involves an increase in cell membrane rigidity via alterations in phospholipid composition. Cis/trans-isomerization of unsaturated fatty acids is considered a short-term response, whereas changes in the saturated-to-unsaturated fatty acid ratio are considered a long-term response to solvent exposure (Heipieper and de Bont, 1994;Heipieper et al, 1996;Loffeld and Keweloh, 1996;Junker and Ramos, 1999). The active removal of toxic compounds from the cell membranes to achieve solvent tolerance occurs via mechanisms such as the formation and expulsion of vesicles loaded with toxic compounds that remove the solvents from the cell surface (Kobayashi et al, 2000) and the extrusion of toxic compounds to the external medium in an energy-dependent process mediated by efflux pumps.…”