Archaebacterial halophiles from alkaline soda lakes were shown to possess substantial amounts of a core diether lipid differing from the C2,,C2, diether lipid characteristic of Halococcus and Halobacterium spp. This novel diether lipid was shown to be an asymmetric C20,C25 diether (2-0-sesterterpanyl-3-0-phytanyl-sn-glycerol). The implications of this unusual lipid for membrane structure are discussed.
I N T R O D U C T I O NExtremely halophilic bacteria of the genera Halobacterium and Halococcus, the methanogens and the thermoacidophilic genera Sulfolobus and Thermoplasma have been designated members of the urkingdom Archaebacteria based on sequencing studies of 16s rRNA (
Whole-organism acid methanolysates of strains of halophilic bacteria were examined for glycerol diether moieties and other long-chain constituents by thin-layer chromatography. Glycerol diether moieties were detected only in acid methanolysates of archaebacterial halophiles. Eubacterial halophiles contained only fatty acid methyl esters. Spots on thin-layer plates attributed to diether moieties were further identified by infrared spectroscopy.Thin-layer chromatographic analysis of whole-organism methanolysates provides a simple and rapid method of distinguishing archaebacterial halophiles from eubacterial halophiles. The majority of archaebacterial halophiles produced only one chromatographically distinct glycerol diether moiety, but certain strains, including the recently described alkalophilic halophiles, produced two distinct moieties.
~ DNA-1 6s rRNA hybridization studies of archaebacterial halophiles revealed nine major groups. High (>45%) DNA-DNA homologies were found only within DNA-rRNA groups. The DNA-DNA homology between the type strains of Halobacterium halobium, Hb. salinarium and Hb. cutirubrum was > 70%. The implications for the taxonomy of the extreme halophiles are discussed.
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