Microbial diversity in evaporite brines

Studies of subterranean ancient evaporites in different geographical and geological habitats around the world have revealed that these sites are populated by abundant populations of halophilic eubacteria. The diversity of these isolates was established by phenotypic, chemotaxonomic and phylogenetic analyses. The majority of the isolates were Gram-negatives (90%), the remainder being Gram-positives as judged by several different kinds of analyses. A numerical taxonomy study of the Gram-negative isolates revealed nine distinct phenons, whereas the Gram-positive isolates were represented by only two phenons. Several of the Gram-negative phenons were distinct from known halophiles included for comparison, confirmed by further chemotaxonomic and phylogenetic analysis. It is suggested that at least three new taxa, probably a genus level, are represented by some of these isolates. Other isolates were closely related to known representatives of the Halomonas group, which are widely distributed in a variety of hypersaline environments. A number of rare archaeal isolates from a particular alkaline hypersaline subterranean site were most closely related to the genus Natronobacterium on the basis of chemotaxonomic and phylogenetic analyses. There was less agreement between phenotypic, chemotaxonomic and phylogenetic analysis for representatives of the two Gram-positive phenons, although the centrotype of one phenon was most closely associated with the same genus Marinococcus and that of the other with the Bacillus spectrum.