Phospholipid biosynthesis and solvent tolerance in Pseudomonas putida strains

Abstract

The role of the cell envelope in the solvent tolerance mechanisms of Pseudomonas putida was investigated. The responses of a solvent-tolerant strain, P. putida Idaho, and a solvent-sensitive strain, P. putida MW1200, were examined in terms of phospholipid content and composition and of phospholipid biosynthetic rate following exposure to a nonmetabolizable solvent, o-xylene. Following o-xylene exposure, P. putida MW1200 exhibited a decrease in total phospholipid content. In contrast, P. putida Idaho demonstrated an increase in phospholipid content 1 to 6 h after exposure. Analysis of phospholipid biosynthesis showed P. putida Idaho to have a higher basal rate of phospholipid synthesis than MW1200. This rate increased significantly following exposure to xylene. Both strains showed little significant turnover of phospholipid in the absence of xylene. In the presence of xylene, both strains showed increased phospholipid turnover. The rate of turnover was significantly greater in P. putida Idaho than in P. putida MW1200. These results suggest that P. putida Idaho has a greater ability than the solvent-sensitive strain MW1200 to repair damaged membranes through efficient turnover and increased phospholipid biosynthesis.

YLR099C (ICT1) Encodes a Soluble Acyl-CoA-dependent Lysophosphatidic Acid Acyltransferase Responsible for Enhanced Phospholipid Synthesis on Organic Solvent Stress in Saccharomyces cerevisiae

“…Enhanced phospholipid biosynthesis was observed on treatment with 4% isooctane, suggesting a correlation between accumulation of membrane phospholipids and tolerance to organic solvent. These data are consistent with tolerance mechanisms exhibited by P. putida Idaho strain (3,5), where the basal level of phospholipid biosynthesis was high on exposure to solvent. Increased phospholipid biosynthesis is a common phenomenon exhibited by organisms to various environmental stresses.…”

“…Organic solvent tolerance mechanism is known to be associated with membrane remodeling in microorganisms (3,24). To understand this phenomenon, we chose S. cerevisiae as the model system.…”

“…Steady accumulation of these solvents in plasma membrane resulted in the loss of structural integrity (3). Because the plasma membrane acts as a selectively permeable barrier of the cell, such a toxicity causes an impairment in the ionic and the metabolic balances, pH gradient, electrical potential, etc., leading to cell lysis.…”

“…Elegant work on mechanisms of solvent tolerance in P. putida strain Idaho showed that the strain was able to repair the damaged membranes through efficient turnover and increased phospholipid biosynthesis. A detailed analysis of phospholipid head group turnover revealed the presence of a large amount of phosphatidylglycerol followed by phosphatidylethanolamine (PE) 3 and cardiolipin. When the P. putida strain was grown in the presence of o-xylene, the amount of PE was high, and it was proposed that the increase in phospholipids was necessary to stabilize the cell membrane structure (3).…”

“…A detailed analysis of phospholipid head group turnover revealed the presence of a large amount of phosphatidylglycerol followed by phosphatidylethanolamine (PE) 3 and cardiolipin. When the P. putida strain was grown in the presence of o-xylene, the amount of PE was high, and it was proposed that the increase in phospholipids was necessary to stabilize the cell membrane structure (3). When Escherichia coli was exposed to 0.25% toluene, a dramatic effect in the ultrastructure of the cell was observed.…”