Description of Silvibacterium acidisoli sp. nov. and Edaphobacter albus sp. nov. and a Proposal for Taxonomic Rearrangements Within the Family Acidobacteriaceae Based on Comparative Genome Analysis

Acidobacteriota are difficult to cultivate but pervasively and copiously distributed across nearly all ecosystems, especially soils, such as agricultural, peat, arctic tundra and metal-contaminated soils. Most of the currently available isolates are affiliated with the family Acidobacteriaceae. However, the current taxonomic structure of Acidobacteriaceae was established based mainly on 16S rRNA gene phylogeny, and several described genera appear to be polyphyletic or taxonomically unresolved. To resolve these issues, genome sequence analyses (18 genomes sequenced in this study and 49 genomes obtained from the NCBI database) along with phenotypic data analysis were used in this study. Phylogenomic analysis and the overall genome relatedness indices (OGRIs)—average nucleotide identity (ANI), average amino acid identity (AAI), percentage of conserved proteins (POCP)—were performed on 67 Acidobacteriota genomes. As a result, proposals for 13 novel combinations are made. Firstly, to resolve the polyphyly of the genus Granulicella, it is suggested that G. aggregans TPB6028T, G. arctica MP5ACTX2T, G. pectinivorans DSM 21001T, G. rosea TPO1014T, G. sapmiensis S6CTX5AT, G. sibirica AF10T and G. tundricola MP5ACTX9T be reclassified to Edaphobacter genus. Secondly, Bryocella elongata is a deep phylogenetic branching pattern of Granulicella elongata comb. nov. Thirdly, due to their deeply phylogenetic branching and low ANI and AAI values, two novel genera, Alloterriglobus gen. nov. and Rhizacidiphilus gen. nov., are proposed, respectively, which encompass Alloterriglobus saanensis comb. nov., Rhizacidiphilus albidus comb. nov. and Rhizacidiphilus tenax comb. nov. Fourthly, Alloacidobacterium dinghuense 4Y35T is placed into genus Pseudacidobacterium. Lastly, based on the phenotypic and genomic data, merging the Terracidiphilus into Occallatibacter genus is proposed. In addition, we describe two novel isolates from forest soil designated ZG23-2T and 4G125T, which are phylogenetically located within this family.