Anoxybacillus voinovskiensis sp. nov., a moderately thermophilic bacterium from a hot spring in Kamchatka

Researchers isolated a novel moderately thermophilic bacterium, designated strain TH13T, from a hot spring biomat in the Voinovskie Hot Springs of Kamchatka, Russia. The isolate is a Gram-positive, facultatively aerobic bacterium that forms non-motile, straight rods and grows optimally at 54°C within a range of 30–64°C. Phenotypic characterization revealed the organism is positive for catalase and oxidase, reduces nitrate to nitrite, and cannot tolerate high salt concentrations or alkaline pH conditions. Phylogenetic analysis based on 16S rRNA gene sequencing placed the isolate within the genus Anoxybacillus, showing closest similarity to A. flavithermus (95.7%), A. gonensis (94.8%), and A. pushchinoensis (94.5%). DNA–DNA hybridization confirmed the isolate was genetically distinct from its nearest relatives, with only 20.6% similarity to A. flavithermus and 30.2% to A. pushchinoensis. The DNA G+C content was 43.9 mol%. Based on these molecular and phenotypic findings, the researchers proposed classifying this isolate as a novel species, Anoxybacillus voinovskiensis sp. nov., named after its collection site.

Key findings

• A novel moderately thermophilic Anoxybacillus species was isolated from a Kamchatka hot spring, growing optimally at 54°C with a range of 30–64°C
• 16S rRNA gene analysis confirmed phylogenetic membership in Anoxybacillus genus with 95.7% similarity to A. flavithermus as the closest relative
• DNA–DNA hybridization demonstrated genetic distinctness with less than 30.2% relatedness to closely related Anoxybacillus species
• The isolate exhibits phenotypic characteristics including facultative aerobic growth, catalase/oxidase positivity, and inability to grow above pH 8 or in high salt concentrations