Fatty acid biosynthesis is involved in solvent tolerance in Pseudomonas putida DOT-T1E

The unusual tolerance of Pseudomonas putida DOT-T1E to toluene is based on the extrusion of this solvent by constitutive and inducible efflux pumps and rigidification of its membranes via phospholipid alterations. Pseudomonas putida DOT-T1E-109 is a solvent-sensitive mutant. Mutant cells were less efficient in solvent extrusion than the wild-type cells, as shown by the limited efflux of ¹⁴C-1,2,4-trichlorobenzene from the cell membranes, despite the fact that the efflux pumps are overexpressed as a result of increased expression of the ttgDEF and ttgGHI efflux pump operons. This limitation could be the result of alterations in the outer membrane because the mutant cells released more β-lactamase to the external medium than the wild-type cells.The mutant P. putida DOT-T1E-109 showed negligible synthesis of fatty acids in the presence of sublethal concentrations of toluene as revealed by analysis of ¹³CH₃-¹³COOH incorporation into fatty acids. In contrast, the mutant strain in the absence of solvents, and the wild-type strain, both in the presence and in the absence of toluene, incorporated ¹³CH₃-¹³COOH at a high rate into de novo synthesized lipids.The mutation in P. putida DOT-T1E-109 increases sensitivity to the solvent because of a limited efflux of the solvent from the cell membranes with the concomitant inhibition of fatty acid biosynthesis.