ESR Studies on the Membrane Properties of a Moderately Halophilic Bacterium

Abstract

Lipid preparations from the cells of a moderately halophilic bacterium, Pseudomonas halosaccharolytica grown under the two extreme conditions of high temperature-high NaCl concentration and low temperature-low NaCl concentration showed distinctively different profiles in phospholipid and fatty acid composition. Cells grown at 40 degrees C in medium containing 3.5 M NaCl had high concentrations of saturated and C19 cyclopropanoic fatty acids (about 50 per cent of the total), whereas cells grown at 20 degrees C in medium containing 0.5 M NaCl had decreased concentrations of these fatty acids with increased concentrations of the corresponding unsaturated fatty acids. The phospholipid composition was also affected ty the culture conditions; cells grown at 40 degrees C in 3.5 M NaCl had large amounts of acidic phospholipids, whereas those grown at 20 degrees C in 0.5 M NaCl had small amounts. ESR studies on liposomes prepared from lipids of cells grown under the two conditions showed characteristic profiles for correlation times and order parameters of three spin labels of stearic acid derivatives similar to those of membranes of whole cells of this bacterium. ESR studies showed that the physical properties of the liposomes from the total extractable lipids and isolated phosphatidylglycerol from the cells were completely different from those of synthetic dioleoylphosphatidylglycerol. Liposomes of the lipids extracted from cells grown at 40 degrees C in 3.5 M NaCl showed change in rotational viscosity on altering the NaCl concentration to 0.5M, whereas liposomes of lipids extracted from cells grown at 20 degrees C in 0.5 M NaCl did not show change in rotational viscosity on increasing the NaCl concentration to 3.5 M.

Derivatives of Holomycin and Cyclopropaneacetic Acid from Streptomyces sp. DT‐A37

“…They are synthesized by cyclopropane synthases, a family of proteins encoded by CFA synthase genes ( cfa gene) that modify the major cell envelope lipids with a diversity of cyclopropane rings. [ ][ ] In bacterial membranes, CFAs fulfill a dual role: stabilizing membranes against adverse conditions (such as high osmotic pressure [ ] and high temperature [ ][ ] ) while simultaneously promoting their fluidity . Finally, all these compounds were evaluated for their antimicrobial activity, cytotoxic activity and inhibitory activity against BRD4 protein.…”

Biology of Moderately Halophilic Aerobic Bacteria

“…When grown in the lower-salinity range (0.5 to 1 M NaCl), PE was twice as abundant as PG, while at high salinity (3 M or more), the amounts of PE and PG were approximately equal (121,122,230,231). At a combination of high temperature and high salt concentration, acidic phospholipids were especially abundant (73.6 mol%), due to an increase in CL and glucosyl-PG levels with a decrease in the PE level (112). Upon entering the stationary growth phase, the content of CL increased at the expense of PG.…”

“…The metabolism of cyclopropane fatty acids was most thoroughly studied in "P. halosaccharolytica" (112,121,122,129,130,167,214,230,231). This species contains 16:0, 16:1, 18:0, 18:1, and 17:0 cyclo and 19:0 cyclo as the major fatty acids (230).…”

A Ring to Rule Them All: The Effect of Cyclopropane Fatty Acids on the Fluidity of Lipid Bilayers

“…3 Fatty acid cyclopropanation occurs in bacteria in response to exposure to adverse environmental conditions. 2,4 Specifically, an increase in the concentration of cyclopropane fatty acids in the membrane of a number of bacteria has been associated with tolerance to high osmotic pressure, 5−8 high temperature, 5,9 low pH, 10−14 nutrient deprivation, 15,16 and high alcohol concentrations. 12,14,17,18 Cyclopropane fatty acids have also been shown to play a role in pathogenesis.…”