Characterization of Terrihabitans soli gen. nov., sp. nov., a Novel 0.2 μm-Filterable Soil Bacterium Belonging to a Widely Distributed Lineage of Hyphomicrobiales (Rhizobiales)

We previously showed that novel filterable bacteria remain in sterile (<0.2 mu m filtered) terrestrial environmental samples from Japan, China, and Arctic Norway. Here, we characterized the novel filterable strain IZ6(T), a representative strain of a widely distributed lineage. Phylogenetic analysis showed that this strain was affiliated with the Rhizobiales (now proposed as Hyphomicrobiales) of Alphaproteobacteria, but distinct from any other type strains. Strain IZ6(T) shared the following chemotaxonomic features with the closest (but distantly) related type strain, Flaviflagellibacter deserti SYSU D60017(T): ubiquinone-10 as the major quinone; phosphatidylethanolamine, phosphatidylcholine, and phosphatidylglycerol as major polar lipids; and slightly high G+C content of 62.2 mol%. However, the cellular fatty acid composition differed between them, and the unsaturated fatty acid (C-18:1 omega 7c/C-18:1 omega 6c) was predominantly found in our strain. Moreover, unlike methyrotrophs and nitrogen-fixers of the neighboring genera of Hyphomicrobiales (Rhizobiales), strain IZ6(T) cannot utilize a one-carbon compound (e.g., methanol) and fix atmospheric nitrogen gas. These findings were consistent with the genome-inferred physiological potential. Based on the phylogenetic, physiological, and chemotaxonomic traits, we propose that strain IZ6(T) represents a novel genus and species with the name Terrihabitans soli gen. nov., sp. nov. (=NBRC 106741(T) = NCIMB 15058(T)). The findings will provide deeper insight into the eco-physiology of filterable microorganisms.

Automated summary

A novel filterable bacterium strain IZ6(T) has been characterized and identified as a representative strain of a widely distributed lineage, showing distinct physiological and chemotaxonomic traits compared to other strains. The strain belongs to a proposed novel genus and species named Terrihabitans soli, with differences in cellular fatty acid composition and inability to utilize certain compounds compared to related strains. These findings provide deeper insight into the eco-physiology of filterable microorganisms.