Genomic metrics analyses indicate that Paenibacillus azotofixans is not a later synonym of Paenibacillus durus.

Paenibacillus durusand Paenibacillus azotofixans, both Gram-stain-positive and endospore-forming bacilli, have been considered to be a single species. However, a preliminary computation of their average nucleotide identity (ANI) values suggested that these species are not synonyms. Given this, the taxonomic attributions of these species were evaluated through genomic and phylogenomic approaches. Although the identity of 16S rRNA gene sequences of P. durus DSM 1735T and P. azotofixans ATCC 35681T are above the circumscription species threshold, genomic metrics analyses indicate otherwise. ANI, gANI and OrthoANI values computed from their genome sequences were around 92 %, below the species limits. Digital DNA-DNA hybridization and MUMi estimations also corroborated these observations. In fact, in all metrics, Paenibacillus zanthoxyli JH29T seemed to be more similar to Paenibacillus azotofixans. ATCC 35681T than P. durus DSM 1735T. Phylogenetic analyses based on concatenated core-proteome and concatenated gyrB, recA, recN and rpoB genes confirmed that P. zanthoxyli is the closest Paenibacillus species to P. azotofixans. A review of the phenotypic profiles from these three species revealed that their biochemical repertoires are very similar, although P. azotofixans ATCC 35681T can be differentiated from P. durus DSM1735T in 13 among more than 90 phenotypic traits. Considering phylogenetic and genomic analyses, Paenibacillus azotofixans should be considered as an independent species, and not as a later synonym of Paenibacillus durus.