Paenibacillus piscarius sp. nov., a novel nitrogen-fixing species isolated from the gut of the armored catfish Parotocinclus maculicauda

A Gram-positive, nitrogen-fixing and endospore-forming strain, designated P121(T), was isolated from the gut of the armored catfish (Parotocinclus maculicauda) and identified as a member of the genus Paenibacillus based on the sequences of the 16S rRNA encoding gene, rpoB, gyrB and nifH genes and phenotypic analyses. The most closely related species to strain P121(T) were Paenibacillus rhizoplanae DSM 103993(T), Paenibacillus silagei DSM 101953(T) and Paenibacillus borealis DSM 13188(T), with similarity values of 98.9, 98.3 and 97.6%, respectively, based on 16S rRNA gene sequences. Genome sequencing revealed a genome size of 7,513,698 bp, DNA G + C content of 53.9 mol% and the presence of the structural nitrogenase encoding genes (nifK, nifD and nifH) and of other nif genes necessary for nitrogen fixation. Digital DNA-DNA hybridization (dDDH) experiments and average nucleotide identity (ANI) analyses between strain P121(T) and the type strains of the closest species demonstrated that the highest values were below the thresholds of 70% dDDH (42.3% with P. borealis) and 95% ANI (84.28% with P. silagei) for bacterial species delineation, indicating that strain P121(T) represents a distinct species. Its major cellular fatty acid was anteiso-C-15:0 (42.4%), and the major isoprenoid quinone was MK-7. Based on physiological, genomic, biochemical and chemotaxonomic characteristics, we propose that strain P121(T) represents a novel species for which the name Paenibacillus piscarius sp. nov. is proposed (type strain = DSM 25072 = LFB-Fiocruz 1636).

Automated summary

A Gram-positive, nitrogen-fixing strain with endospore-forming abilities was isolated from the gut of the armored catfish. Through genetic and phenotypic analysis, it was identified as a member of the Paenibacillus genus. Genome sequencing and DNA-DNA hybridization experiments confirmed that it represents a distinct species.