INFLUENCE OF COLD SHOCK ON THE FATTY-ACID COMPOSITION OF DIFFERENT LIPID CLASSES OF THE FOOD-BORNE PATHOGEN LISTERIA-MONOCYTOGENES

Listeria monocytogenes, a Gram-positive pathogenic food-borne bacteriu m, is notably resistant to chill and osmotic stress. Listeria is chara cterized by an unusual proportion of branched-chain fatty acid (>85%), primarily anteiso-15:0 and anteiso-17:0. Cells grown at lower tempera tures contain significantly less anteiso-17:0 than those grown at high er temperature. Cold-shock studies were performed to determine the mec hanisms by which Listeria perceives cold shock and changes its membran e composition. This study made three comparisons: (i) The lipids of L. monocytogenes cultured at 30 degrees C were compared with those of ce lls grown at 6 degrees C. Extraction of total lipids yielded 4-4.5 and 6.5-7 mg ml(-1) cell mass (wet weight), respectively. Total lipids co ntained 3-4% and 2-2.5% lipid phosphorus, respectively, reflecting a h igher content of neutral lipids in cells grown at 6 degrees C. iii) Th e fatty-acid compositions of different lipid classes (total lipids, th e major phospholipid, and the glyco-containing phospholipid class) all responded by increasing the proportion of anteiso-15:0 fatty acids at low temperature. (iii) The fatty-acid composition of the neutral and polar lipids from the early stage of the temperature response (3 days at 5 degrees C) and the effect of chloramphenicol or cerulenin were ex amined. The results indicated that anteiso-15:0 fatty acids were selec tively increased in the newly synthesized neutral lipids, but the pola r lipids did not show an apparent change in fatty-acid composition. Th ese changes in membrane fatty-acid composition did not require new pro tein synthesis (the process was chloramphenicol insensitive) and the e xisting condensing enzyme activity was necessary to the fatty-acid res ponse (the process was cerulenin sensitive). (C) 1998 Academic Press.