Thermophilic Bacteria: Their Relationships to Other Bacteria and Role in Archaebacterial and Eubacterial Evolution

The main goal of the present study is to examine what effect the thermophilic condition had on the early evolution of the cell and, specifically, to identify any possible molecular constraints this condition placed on the ribosomal RNA. During the past year we have characterized the 16S ribosomal RNAs from several novel thermophilic isolates provided by Prof. Karl Stetter in addition to isolates from various other sources. The rRNA has been directly sequenced by the dideoxy termination method using reverse transcriptase and primers designed specifically for the 16S rRNA molecule. The thermophiles examined have been isolated from a wide variety of thermophilic niches in sources geographically removed from one another e.g. the Red Sea, Indonesia, Azores, deep sea vents. Although isolated from varied and distinct thermophilic habitats, the new bacterial strains are generally representative of previously defined phylogenetic groups. This agrees with our earlier observation that there appears to be relatively limited phylogenetic diversity in thermophilic niches, as determined from the organisms thus far isolated from these environments. Keywords Archaebacteria, Eubacteria, Thermophilic bacteria.