Geobacillus subterraneus subsp. aromaticivorans subsp. nov., a novel thermophilic and alkaliphilic bacterium isolated from a hot spring in Sırnak, Turkey.

A new thermophilic spore-forming strain Ge1(T) was isolated from the Guclukonak hot spring in Sırnak, Turkey. The strain was identified by using a polyphasic taxonomic approach. Strain Ge1(T) was Gram-positive, spore-forming, alkaliphilic rod-shaped, motile, occurring in pairs or filamentous. Growth was observed between 30 and 65°C (optimum 60°C) and at pH 5.5-10.0 (optimum pH 9.0). It was capable of utilizing starch, growth was observed at 0-3% NaCl (w/v) and was positive for catalase and urease. The major cellular fatty acids were iso-C(15:0) and iso-C(17:0), and the predominant lipoquinone found was menaquinone MK7 type. The DNA G+C content of the genomic DNA of strain Ge1(T) was 52.0%. Comparative 16S rRNA gene sequence studies showed that the isolate belonged to the genus Geobacillus. The DNA-DNA hybridization mean values between the representative strain Ge1(T) and the closely related species G. subterraneus, G. thermodenitrificans, G. thermocatenulatus, G. vulcani and G. thermoleovorans were 69.3%, 57%, 37%, 27% and 26%, respectively. The results of DNA-DNA hybridization, physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain Ge1(T). Based on these results, we propose assigning a novel subspecies of Geobacillus subterraneus, to be named as Geobacillus subterraneus subsp. aromaticivorans subsp. nov. with the type strain Ge1(T) (DSM 23066 (T)= CIP 110341(T)).