Revisiting the taxonomy of the genus Rhodopirellula with the proposal for reclassification of the genus to Rhodopirellula sensu stricto, Aporhodopirellula gen. nov., Allorhodopirellula gen. nov. and Neorhodopirellula gen. nov.

Abstract

The current genus Rhodopirellula consists of marine bacteria which belong to the family Pirellulaceae of the phylum Planctomycetota. Members of the genus Rhodopirellula are aerobic, mesophiles and chemoheterotrophs. The here conducted analysis built on 16S rRNA gene sequence and multi-locus sequence analysis based phylogenomic trees suggested that the genus is subdivided into four clades. Existing Rhodopirellula species were studied extensively based on phenotypic, genomic and chemotaxonomic parameters. The heterogeneity was further confirmed by overall genome-related indices (OGRI) including digital DNA-DNA hybridization (dDDH), average nucleotide identity (ANI), average amino acid identity (AAI), and percentage of conserved proteins (POCP). AAI and POCP values between the clades of the genus Rhodopirellula were 62.2-69.6% and 49.5-62.5%, respectively. Comparative genomic approaches like pan-genome analysis and conserved signature indels (CSIs) also support the division of the clades. The genomic incoherence of the members of the genus is further supported by variations in phenotypic characteristics. Thus, with the here applied integrated comparative genomic and polyphasic approaches, we propose the reclassification of the genus Rhodopirellula to three new genera: Aporhodopirellula gen. nov., Allorhodopirellula gen. nov., and Neorhodopirellula gen. nov.