title: ESR studies on the membrane properties of a moderately halophilic bacterium. II. Effect of extreme growth conditions on liposome properties.
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.
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D005227:Fatty Acids / Q000032:analysis*; D008081:Liposomes / Q000032:analysis*; D009994:Osmolar Concentration; D010743:Phospholipids / Q000032:analysis*; D011549:Pseudomonas / Q000032:analysis* / Q000254:growth & development; D012492:Salts; D012965:Sodium Chloride; D013696:Temperature
chemical_list: D005227:Fatty Acids; D008081:Liposomes; D010743:Phospholipids; D012492:Salts; D012965:Sodium Chloride