PHYLOGENETIC ANALYSES OF SOME EXTREMELY HALOPHILIC ARCHAEA ISOLATED FROM DEAD-SEA WATER, DETERMINED ON THE BASIS OF THEIR 16S RIBOSOMAL-RNASEQUENCES

Twenty-two extremely halophilic aerobic archaeal strains were isolated from enrichments prepared from Dead Sea water samples collected 57 ye ars ago, The isolates were phenotypically clustered into five differen t groups, and a representative from each group was chosen for further study, Almost the entire sequences of the 16S rRNA genes of these repr esentatives, and of Haloarcula hispanica ATCC 33960, were determined t o establish their phylogenetic positions, The sequences of these strai ns were compared to previously published sequences of 27 reference hal ophilic archaea (members of the family Halobacteriaceae) and two other archaea, Methanobacterium formicicum DSM 1312 and Methanospirillum hu ngatei DSM 864, Phylogenetic analysis using approximately 1,400 base c omparisons of 16S rRNA-encoding gene sequences demonstrated that the f ive isolates clustered closely to species belonging to three different genera-Haloferax, Halobacterium, and Haloarcula. Strains E1 and E8 we re closely related and identified as members of the species Haloferax volcanii, and strain E12 was closely related and identified as a membe r of the species Halobacterium salinarum. However, strains E2 and E11 clustered in the Haloarcula branch with Haloarcula hispanica as the cl osest relative at 98.9 and 98.8% similarity, respectively, Strains E2 and E11 could represent two new species of the genus Haloarcula, Howev er, because strains of these two new species were isolated from a sing le source, they will not be named until additional strains are isolate d from other sources and fully characterized.