CHARACTERIZATION OF THE DOMINANT HALOPHILIC ARCHAEA IN A BACTERIAL BLOOM IN THE DEAD-SEA

A mass bloom of halophilic archaea developed in the Dead Sea in the su mmer of 1992, with peak densities of more than 3 x 10(7) cells/ml, imp arting a red coloration to the water. Microscopical examination showed a numerical dominance of pleomorphic, flat cells. Attempts to identif y the dominant type of halophilic archaea by means of growth experimen ts, both on agar plates and by dilution in liquid media, were unsucces ful, as viable counts obtained were two or more orders of magnitude lo wer than the total microscopic counts. Analysis of the polar lipids in the Dead Sea biomass during the bloom showed one major glycolipid to be present in the extracts, corresponding with the sulfated diglycosyl diether lipid (S-DGD-1) characteristic of the genus Haloferax. No ind ications were found for the presence of significant amounts of other g lycolipids that indicate the presence of large numbers of Dead Sea arc haea such as Halobacterium sodomense or Haloarcula marismortui, or Hal obacterium species such as H. halobium, H. salinarium and H. saccharov orum. Thus, the numerically dominant organism in the bloom is probably a difficult to culture, not yet isolated, representative of the genus Haloferax.