Characterization and identification of Geobacillus spp. isolated from Soldhar hot spring site of Garhwal Himalaya, India

13 morphologically distinct strains of thermophilic bacteria isolated from a hot spring site in Garhwal region of Indian Himalaya have been characterized and identified using phenotypic and genotypic characters. All the strains developed circular to irregular colonies between 2-3 mm on Tryptone Yeast extract (TY) agar plates at 65 degrees C following 24-36 h incubation. In TY broth, facultative bacterial growth was observed within 12-16 h of incubation at 65 degrees C. The bacterial strains could tolerate a temperature range between 40-45 degrees C to 85-90 degrees C (optimum 65-70 degrees C) and pH between 4-11 (optimum 6-8). The cell morphology varied from short to long rods arranged in single, diplobacilli (in V or L shape) or short or long spiral chains with coiling. The bacterial strains varied in respect of their biochemical tests conducted for various enzymes, fermentation of sugars, tolerance to antibiotics and salt. Based on the 16S rRNA analysis, 11 strains showed maximum similarity with Geobacillus stereothermophilus, one strain with G. kaustophilus and one with Geobacillus sp.