Comparative genomics of Parolsenella catena and Libanicoccus massiliensis: Reclassification of Libanicoccus massiliensis as Parolsenella massiliensis comb. nov.

Previous analyses based on 16S rRNA and hsp60 genes indicated that Parolsenella catena and Libanicoccus massiliensis were closely related to each other and formed a monophyletic cluster independent of the related Olsenella species. To clarify the relationship of these two species, we determined the genome sequence of P. catena JCM 31932 T and compared it with that already sequenced for L. massiliensis Marseille-P3237 T . Phylogenetic trees based on the concatenated 37 single-copy ribosomal proteins or RpoB robustly supported the relationship observed in the previous studies. Digital DNA–DNA hybridization and average nucleotide identity (ANI) values between P. catena JCM 31932 T and L. massiliensis Marseille-P3237 T were 32.6 and 87.8 %, respectively, indicating that P. catena JCM 31932 T and L. massiliensis Marseille-P3237 T are independent species. Alignment fraction and ANI values between the two genomes were 0.75 and 88.84 %, respectively, thus indicating that the two species should be classified into the same genus. The number of putative orthologous genes shared between the two genomes was 1321, which was significantly larger than those (482–928) reported between L. massiliensis Marseille-P3237 T and other closely related species. In addition, the genome of P. catena JCM 31932 T had a high degree of synteny conservation with that of L. massiliensis Marseille-P3237 T . On the basis of these findings, we propose that L. massiliensis should be reclassified as Parolsenella massiliensis comb. nov.; the type strain is Marseille-P3237 T (=JCM 33000 T =CCUG 71182 T ).