A thermophilic, spore-forming, rod-shaped bacterium isolated from the Yumthang hot spring in North Sikkim, India was subjected to taxonomic studies. The thermophilic bacterial isolate was designated as strain AYN2T. Cells were Gram-stain-positive, aerobic, motile, rod-shaped, catalase-positive and methyl red-negative. Strain AYN2T was able to grow in the pH range from 6 to 10 (optimum, pH 7.5-8.0), at 40-70 °C (60 °C) and in NaCl concentrations of 0-4 % (1 %). The major cellular fatty acids were iso-C15 : 0 (12.8 %), iso-C16 : 0 (13.9 %) and iso-C17 : 0 (13.8 %). No matches were found in the rtsba6 Sherlock libraries. The G+C content of the genomic DNA was 42.11 mol%. Based on phylogenetic analysis of the 16S rRNA gene sequences, strain AYNT showed highest sequence similarity to the type strain of Geobacillus toebii (96 %). However, the phenotypic properties of strain AYN2T were clearly distinct from those of G. toebii and related species. On the basis of polyphasic analysis, strain AYN2T represents a novel species in the genus Geobacillus, for which the name Geobacillus yumthangensis sp. nov. is proposed. The type strain is AYN2T(MTCC=12749=KCTC=33950= JCM 32596).
Keywords: Geobacillus yumthangensis sp. nov.; Sikkim; hot spring; polyphasic taxonomy; thermophiles.