Lipid modulation by environmental stresses in two models of extremophiles isolated from Antarctica

Thermoacidophilic and halotolerant microorganisms from the Antarctic contin ent were studied for their lipid modulation under stress growth conditions. Temperature-induced changes in complex lipids and fatty acids of four stra ins belonging to the genus Alicyclobacillus involved the relative proportio ns of different polar lipids and the synthesis of omega -cyclohexyl-acyl ch ains, which were favoured by high temperatures. Studies were carried out on the lipid composition of four strains of extremely halotolerant bacteria b elonging to the genus Micrococcus grown at different salt concentrations fr om 0 up to 4.5 M NaCl. The main lipids found were two unidentified glycolip ids and two phospholipids: 1,2 diacylglycero-3-phosphoryl-glycerol (PG) and cardiolipin (DPG). Among the strains analysed, the lipids of the Micrococc us strain Erebus were shown to be strongly influenced by salt concentration s, in that DPG and one glycolipid were absent at a low salt molarity while, under these conditions, PG was the main lipid found. The predominant fatty acids in all halotolerant strains were of the anteiso type; growth under i ncreasing salinity gave rise to an increase in long chain fatty acids and o f straight chain fatty acids, while a decrease in iso fatty acids occurred.