Phylogenetic analysis of the bacterial community in a geothermal spring,Rupi Basin,Bulgaria

Hot environments are between the supporting life extreme niches that appear to have maintained some degree of pristine quality and of special biotechnological interest. Knowledge on biodiversity in terrestrial hot springs is still scanty and has not been compared in the light of the specificity of those extreme ecological niches. Study on diversity of thermophilic bacteria inhabiting a hot spring located in Rupi Basin (RB), South-West Bulgaria, revealed a high phylogenetic richness in it (genotypic diversity is 0.37). A total of 120 clones were examined, and grouped in 28 phylogenetic types by their RFLP profile. 16S rRNA gene analysis allowed the identification of nine divisions from the domain Bacteria and one Candidate division. Ten of the retrieved bacterial sequences representing one third of the sequence types showed less than 97% similarity to the closest neighbor and were referred as new sequences. Four of them were distantly related to validly described bacteria (showed ≤90% similarity) suggesting new taxons on at least genus level. Comparison of biodiversity in the spring from Rupi Basin, Bulgaria with that described from other terrestrial hot springs revealed that Proteobacteria, Hydrogenobacter/Aquifex and Thermus are common bacterial groups for terrestrial hot springs. Simultaneously, specific bacterial taxons were observed in different springs.