Paenibacillus sinensis sp. nov., a nitrogen-fixing species isolated from plant rhizospheres

Two strains HN-1(T) and 39 were isolated from rhizospheres of different plants grown in different regions of PR China. The two strains exhibited high nitrogenase activities and possessed almost identical 16S rRNA gene sequences. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the two strains were 99.9 and 99.8%, respectively, suggesting that they belong to one species. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strains HN-1(T) and 39 are the members of the genus Paenibacillus and both strains exhibited 99.5% similarity to Paenibacillus stellifer DSM 14472(T) and the both strains represented a separate lineage from all other Paenibacillus species. However, the ANI of type strain HN-1(T) with P. stellifer DSM 14472(T) was 90.69, which was below the recommended threshold value (< 95-96% ANI). The dDDH showed 42.1% relatedness between strain HN-1(T) and P. stellifer DSM 14472(T), which was lower than the recommended threshold value (dDDH < 70%). The strain HN-1(T) contain anteiso-C-15:0 as major fatty acids and MK-7 as predominant isoprenoid quinone. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, four aminophospholipids and an unidentified glycolipid. Unlike the most closely related P. stellifer DSM 14472(T), strain HN-1(T) or 39 was positive for catalase reaction. Distinct phenotypic and genomic characterisations from previously described taxa support the classification of strains HN-1(T) or 39 as representatives of a novel species of the genus Paenibacillus, for which the name Paenibacillus sinensis is proposed, with type strains HN-1(T) (=CGMCC 1.18902, JCM 34,620), and reference strain 39 (=CGMCC 1.18879, JCM 34,616), respectively.

Automated summary

Two strains HN-1(T) and 39 isolated from different plant rhizospheres in China were found to have high nitrogenase activities and nearly identical 16S rRNA gene sequences, indicating they belong to the same species. They were identified as a novel species of the genus Paenibacillus, named Paenibacillus sinensis, based on distinct phenotypic and genomic characteristics, despite their close relationship to Paenibacillus stellifer.