The lack of dam gene inducesmodification on the lipidsmembrane composition of Salmonella typhimuriumexposed to theOx bile extract
Aloui Amine, Landoulsi Ahmed
Unité de recher che de Biochimie des lipides et interactions avec les macromolécules. 03/UR /0902. L aboratoire de
Biochimie et de Biologiemoléculaire, F aculté des sciences de Bizer te, 7021, Zar zouna, (T UNI SI E )
The effect of methylation on the bacterial growth, the phospholipids (PL) and the membrane fatty acid (FA) composition in S.Typhimuriumwild type (WT) and dam- mutant strains exposed to the ox bile extract (OBE) stress was examined. Phosphatidylethanolamine (PE) Cardiolipin (CL), and Phosphatidylglycerol (PG) are the major PL present in all the strains and accounted for greater than 95% of the total lipid (TL) phosphorus. Phosphatidic acid and phosphatidylserine are the minor ones. The OBE stress highly affected the growth rate of the dam- mutant and its PL contents. We noticed a great increase in the acidic PL proportion (CL and PG) and an unusual decrease in PE compared with the untreated damand the isogenic WT strains. FA composition of the TL and the different fractions containing PLwere altered.Moreover, OBE stress combined with the dam mutation caused an increase in the ration of unsaturated to saturated fatty acids (UFA/SFA) and there was an increase in the content of palmitoleic acid (C16:1w7) and oleic or vaccenic acid (C18:1w9). This increase in UFA content was compensated by a decrease in the corresponding cyc17 and cyc19 cyclic FA (CFA). So these CFA were converted to UFA, which resulted in a high UFA/SFAratio. Based on these observations, we suggest that the Dam protein might regulate biosynthesis ofmembrane lipids of S.Typhimuriumand it is required for membrane protection from bile salts during bacterial growth and infection process.
S.Typhimurium; Fatty acids; Phospholipids; OBE stress; Damenzyme; Methylation.