Membrane lipid alterations and thermal stress in Salmonella typhimurium 7136.

Salmonella typhimurium ATCC 7136 exhibited major changes in lipid composition when grown in the presence of either 0.15% sodium deoxycholate or 0.15% sodium benzoate. These lipophilic compounds had directly opposing effects on the lipid profile of the organism. The saturated/unsaturated ratio was markedly elevated in benzoate-grown cells. On the other hand, it was depressed by an even greater margin from the control after growth in the presence of deoxycholate. Adjustments in the phospholipid content of the cells were also recorded. Phosphatidylethanolamines decreased by 28 and 50% in the deoxycholate- and benzoate-grown cells, respectively. Compensatory increases in phosphatidylglycerols of 87.5 and 175% occurred, along with increases in cardiolipins of 12- and 22-fold, respectively. Deoxycholate or benzoate supplementation also altered the relative distribution of neutral lipids; again, benzoate stimulated the greater change. Compositional changes were accompanied in the organism by increased heat sensitivity, but the effect on the susceptibility of S. typhimurium to injury varied with the physical properties of the supplement used.