Survey of lipids of a new group of extremely halophilic bacteria from salt ponds in Spain

Abstract

The lipids of 8 strains of a new group of extreme halophiles isolated from Spanish salt ponds were studied in comparison with those of Halobacterium cutirubrum, H. halobium, H. salinarium, H. marismortui, H. saccharovorum and H. vallismortis. All strains showed the presence of C30 isoprenoids (squalene, dihydrosqualene and tetrahydrosqualene), C40 carotenes (.beta.-carotene), C50 pigments (bacterioruberins) and vitamin MK-8. All polar lipids were derivatives of 2,3-di-O-phytanyl-sn-glycerol. Diphytanyl glycerol ether analogues of phosphatidyglycerol and phosphatidylglycerophosphate were also present in the strains but sulfated glycolipids were found in only 6 strains: 2 had a sulfated tetraglycosyl diether, a sulfated triglycosyl diether and possibly a sulfated diglycosyl diether, whereas the other 7 had only sulfated diglycosyl diether. All strains contained diglycosyl diphytanyl diether. Significantly large amounts of the diphytanyl glycerol ether analogue of phosphatidylglycerosulfate were present in 4 strains. Strain R-4 exhibited marked changes in contents of individual pigments, but not in total lipids, when grown in different salt concentrations. In 15% salt it produced 18- to 19-fold more bacterioruberin than when grown in 25 or 35% salt. Similar reductions in the amounts of other C50 pigments and .beta.-carotene were also observed. No significant changes in the contents of squalenes and vitamin MK-8 were observed. H. cutirubrum produced C50 pigments and .beta.-carotene only when grown in salt concentrations greater than 15%. Possible ecological consequences of the changes in pigmentation with salt concentration are discussed.