Paenibacillus borealis sp. nov., a nitrogen-fixing species isolated from spruce forest humus in Finland.

Seven spore-forming, nitrogen-fixing bacterial isolates from spruce forest humus in Finland were studied using the polyphasic approach. PCR amplification of 16S rRNA gene fragment with specific primers showed that the isolates were members of Paenibacillus. Levels of 16S rDNA similarity between the isolates were 97.3-100.0% and those between the isolates and other Paenibacillus species were 90.3-96.5%. The highest similarities were observed with Paenibacillus azotofixans and Paenibacillus durus. Ribotyping with EcoRI and PvuII restriction showed a high diversity in the Paenibacillus species and distinguished the isolates from these closely related species. The main whole-cell fatty acids were anteiso-C15:0 (33-48%), straight-chain C14:0 (7-21%) and C16:0 (9-20%), and iso-C15:0 (6-15%). Electron microscopy revealed a unique striped morphology of the spore surfaces. Based on phylogenetic inference and phenotypic and chemotaxonomic characteristics, these isolates are proposed as a new species, Paenibacillus borealis sp. nov., the type strain of which is KK19T (= DSM 13188T = CCUG 43137T).