Influence of pH and incubation temperature on fatty acid composition and virulence factors of Yersinia enterocolitica

The fatty acid extracts of three strains of Yersinia enterocolitica grown at pH 5, 7 and 9 and incubated at 4 and 20 degrees C were examined using gas chromatography. When cultured at pH 5, Y, enterocolitica produced increased proportions of cyclopropane and saturated fatty acids and decreased amounts of unsaturated fatty acids as compared with levels produced during growth at pH 9. At pH 5, saturated fatty acids comprised 73-86% of the total fatty acids, whereas at pH 9, saturated fatty acids decreased to 47-72% of the total fatty acids. Generally, Y. enterocolitica strains exhibited a reduced proportion of cis-16:1(9) as pH was reduced accompanied by a significantly higher level (P<0 . 05) of 17:0 Delta with increasing pH. Temperature had a significant effect (P<0 . 01) on the production of the unsaturated fatty acids, cis-16:1(9) and cis-18:1(9). Indicator tests for virulence demonstrated that strain YE321 (serotype 0:20) lost its virulence factor, whereas strains YE133 (serotype 0:8) and YE228 (serotype 0:3) retained their virulence markers following incubation at 4 and 20 degrees C at pH 5, 7 and 9. No characteristic trends in fatty acid profiles were observed when plasmid-bearing strains and the strain that lost its virulence plasmid were compared, suggesting that virulence plasmid stability and fatty acid composition are independent. (C) 1996 Academic Press Limited.