Changes in fatty acid composition of cellular lipids of Aeromonas spp. due to temperature and pH

Fatty acid methyl ester (FAME) profiles of cellular lipids can be used to identify aeromonads and other bacteria. Various conditions may alter FAME profiles of bacteria. However, effect of pH and temperature changes during growth on FAME profiles of aeromonads have not been investigated. The objective of this study was to determine the effects of temperature, pH and age of culture on FAME of aeromonads involved in human gastroenteritis.

Fatty acid profiles varied significantly (p<0.05) within species of Aeromonas. However, the level of 16:1 was always greater than 16:0, and levels of 20:0 were always greater than 10% of the total FAME at pH 5.0 and 7.0. Changes in pH and/or temperature significantly affected the FAME profiles of the six strains studied. Total lipid content increased as temperature increased but decreased as pH increased.

Changes in pH of culture media and temperature of growth affected the FAME profiles of Aeromonas spp. to the point of misidentification since strains within the same species varied significantly with changes in pH and temperature. FAME profiles of aeromonads under some pH/temperature combinations resembled other genera such as Yersinia.