Characterization of the halophilic archaeal community in saltern crystallizer ponds by means of polar lipid analysis

Saltern crystallizer ponds are coloured red due to the presence of dense communities of red halophilic archaea (family Halobacteriaceae). Little quantitative information exists on the species distribution within the archaeal community in such ponds. As the different genera of the Halobacteriaceae differ in polar lipid content, and especially in the types of glycolipids, lipid analysis can be used to obtain information on the nature of the organisms present. Analysis of the polar lipids extracted from the biomass collected from the saltern crystallizer ponds in Eilat, Israel, showed one major glycolipid to be present, co-chromatographing with the sulfated diglycosyl diether lipid characteristic of the genus Haloferax. No indications were found for the presence of significant amounts of those glycolipids that would indicate the presence of large numbers of other archaea such as Halobacterium species (H. cutirubrum and H. salinarium, characterized by sulfated triglycosyl and tetraglycosyl diethers), or Haloarcula species (possessing a triglycosyl diether). Phosphatidyl glycerosulfate, a polar lipid absent in Haloferax species, was present in the lipid extract from the crystallizer ponds, suggesting that the dominant microorganism present may be related to strains which are presently classified in the genus Halobacterium but are awaiting a taxonomic reappraisal (H. sodomense, H. saccharovorum, and H. trapanicum). Organisms of the latter group are characterized by sulfated diglycosyl diethers, and the presence of phosphatidyl glycerosulfate. Attempts to isolate the dominant type of bacterium on agar plates yielded relatively low counts (1-2 orders of magnitude lower than the numbers observed microscopically) of bacteria, and most of the isolates had a polar lipid composition characteristic of the H. salinarium group or the H. sodomense-H. saccharovorum-H. trapanicum group.