The polar lipid composition of Walsby's square bacterium

Square, gas vacuole-containing Archaea of the type first described by Walsby were found to dominate in a saltern crystallizer pond in Eilat, Israel. To obtain information on the taxonomic position of these yet uncultured bacteria, we analyzed the polar lipids present in the microbial community in the saltern brine. In addition to phosphatidylglycerol, phosphatidylglycerophosphate and phosphatidylglycerosulfate we found one glycolipid, chromatographically identical with the sulfated diglycosyl diether lipid found as the major glycolipid in Haloferax species. As the square bacteria contributed at least 85% of the total membrane surface in the biota of the sample examined, we concluded, based on polar lipid composition, that these organisms are unrelated to the genera Halobacterium and Haloarcula, and probably belong to a new genus.