Membrane fluidity of Pseudomonas putida and its relation with the tolerance to cationic surfactants

HEREDIA R.M; LOPÉZ G.A; BOERIS P.S.; LUCCHESI G.I.

Congreso; 50 Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2014

Adaptive response of P. putida to tetradecyltrimethylammonium (TTAB) involves changes in the content of phospholipids (PL) and fatty acid (FA) of the membrane. Phosphatidylglycerol (PG) and phosphatidic acid increased and cardiolipin (CL) decreased. The levels of unsaturated FA (UFA) decreased significantly while the amount of saturated FA (SFA) increased. Consequently, the SFA/UFA ratio increased 6 fold, indicating decreased the degree of fluidity of the cell of membrane. CL, one of the major PL in P. putida, carries highest content of UFA (18%). In order to assign a role to CL in the response to TTAB, a double mutant strain affected in the genes responsible for the synthesis of CL was obtained and characterized. Compared with the wild-type, the fluorescence polarization showed that the membrane of the mutant strain was more rigid (P=0.22), with high reduction in CL content (1.9% of total PL) and with UFA content similar to detected in the parental strain (9.8% and 11%, respectively), although distributed mainly in PG. When the mutant strain was exposed to TTAB, the P value was 0.14, the UFA content increased (16.5%) and the amount of viable cells decreased from 1012 ufc ml-1 to 106 ufc ml-1, demonstrating that the fluidizing effect of surfactant cannot be counteracted. The set of results indicate that an adequate level of CL is indispensable in the cell?s response to TTAB.