Phylogenetic Study of Haloanaerobic Bacteria by 16S Ribosomal RNA Sequences Analysis

The nucleotide sequences of 16S rRNA of four strains of the haloanaerobic bacteria Haloincola saccharolytica Acetohalobium arabaticum, Halobacteroides lacunaris, and Halobacteroides sp. have been determined. The phylogenetic analysis employing the MTP method placed the group of the haloanaerobes in a single cluster at the base of a branch leading to the Gram-positive organisms on the constructed unrooted tree. However, an additional analysis demonstrated that the cluster of the haloanaerobes did not belong to any subdivision of Gram-positive bacteria, including the representatives of the Gram-negative branches — Heliobacterium and Sporomusa. The signature analysis and the secondary structure analysis of the 16S rRNA of the haloanaerobes revealed some peculiarities that distinguish them from the other bacterial phyla. All these data along with the unique phenotype of these microorganisms demonstrate that the haloanaerobes represent a separate line of descent within the Bacteria.