Genome-wide analysis of Geobacillus strains revealed their taxanomic and physiological features under extreme environments

Strains in the genus of Geobacillus are found in a variety of thermophilic environments such as geothermal hot springs, subterranea, and high temperature oil fields. The Geobacillus strains are moderately thermophilic, gram-positive, endospore-forming rods, aerobic, or facultatively anaerobic. It has been known that they can grow in the range of 35^oC to 78^oC (with optimal growth temperature of 50~60^oC) and neutral pHs (6.5~7.8). Intriguingly, their 16S ribosomal RNA sequences are highly conserved (identity of >99%), but their fermentative and metabolic features for carbohydrate utilization are quite variable. Herein we sequenced and compared the genomes of G. kaustophilus HTA426, G. thermoleovorans ID-1, G. thermocatenulatus KCTC 3921, G. subterraneus KCTC 3922, G. caldoxylosilyticus CIC9, G. lituanicus N-3, and Aeribacillus pallidus to assess their taxonomy and phylogeny based on carbohydrate utilization. In addition, we also investigated their growth phenotypes together with total protein expression patterns and fermentation products. To our knowledge, this is the first comparative genomics on the Geobacillus strains, providing an insight into lifestyle adaptation, prophage diversity, and carbohydrate metabolism under thermophilic environments.