Emended description of the genus Rhizobacter and reclassification of Ideonella sakaiensis as Pseudideonella sakaiensis gen. nov., comb. nov.

Due to the lack of available genomes for all species in the genus Rhizobacter , the taxonomic status of this genus is still unclear at present. In this study, the genomes of all species in the genus Rhizobacter were sequenced and phylogenomic analyses clearly indicated that this genus should belong to the family Sphaerotilaceae . The Rhizobacter species, Piscinibacter species and Ideonella sakaiensis formed an intermingled cluster in the phylogenomic trees, implying that the taxonomic status of some taxa was ambiguous. Notably, Piscinibacter gummiphilus , Piscinibacter koreensis and Piscinibacter terrae formed a tight clade with Rhizobacter species in the phylogenomic trees. P. gummiphilus originated from the reclassification of Rhizobacter gummiphilus in 2022. The AAI value between P. gummiphilus and Rhizobacter dauci was 81.3%, which exceeded the established Sphaerotilaceae -specific thresholds for genus delineation, supporting the restoration of P. gummiphilus to the genus Rhizobacter . The similar genotypic characteristics and close phylogenetic relationships among P. koreensis , P. terrae and Rhizobacter species also supported the transfer of both species to the genus Rhizobacter . In contrast, I. sakaiensis exhibited a distinct phylogenetic position whether in the 16S rRNA gene tree or phylogenomic trees. Its G+C content was 72.9%, which was significantly higher than that of Rhizobacter and Piscinibacter species. Only I. sakaiensis harboured both poly(ethylene terephthalate) hydrolase and mono(2-hydroxyethyl) terephthalate hydrolase simultaneously. Considering its unique degradation ability for poly(ethylene terephthalate) and genotypic characteristics, it was reasonable to reclassify this species as Pseudideonella sakaiensis gen. nov., comb. nov.