Effects of temperature and salt on lipid and fatty acid compositions of a bacterium isolated from the bottom layer of lake vanda, antarctica.

Abstract

A Gram-negative, aerobic bacterium isolated from the bottom layer of Lake Vanda, Antarctica, can grow in a synthetic medium containing biotin as a growth factor. The lipid and fatty acid compositions of the cells grown in the fatty acid-free medium were analyzed. Phosphatidylethanolamine, phosphatidylglycerol and wax esters were identified as major components of the chloroform-methanol extractable lipids. Palmitoleic and oleic acids comprised more than 90% of the total fatty acid of the lipids when the bacterium was grown at low temperature (5°C). Increasing the growth temperature induced an increase in the average fatty acyl chain length of the phospholipids and a decrease in the unsaturation degree of the fatty acyl chain of the wax esters. Increasing the NaCl concentration in the medium also induced an increase in the average fatty acyl chain length of the phospholipids. The effects of temperature and NaCl were compared further at the level of phospholipid molecular species. The sn-2 position of phosphatidylethanolamine and the sn-1 position of phosphatidylglycerol were the most sensitive sites to changes of temperature and NaCl concentration, respectively. An aerobic desaturase system was demonstrated to be the only pathway for unsaturated fatty acid synthesis in this bacterium.