Metagenomics indicates new taxa in Candidatus Saccharimonadia and proposal of Parviradicicola hetaonensis gen. nov. sp. nov. and Parviputeicola dengkouensis gen. nov. sp. nov. following the rules of the SeqCode.
Candidatus Saccharimonadia is a core lineage within the phylum Patescibacteriota (formerly the bacterial candidate phyla radiation, CPR), yet the class has long lacked a standardized, complete taxonomic framework. This nomenclatural gap severely hinders consistent academic exchange and global research into its diversity, evolutionary history, and ecological roles. Here, we recovered 29 medium- to high-quality Ca. Saccharimonadia metagenome-assembled genomes (MAGs) from groundwater, rhizosphere soil, and saline-alkali soil in the Hetao Irrigation District, Inner Mongolia, China, and performed integrated phylogenomic, genome size evolution, and metabolic analyses alongside reference genomes from the GTDB r220 database. Based on robust polyphasic taxonomic evidence (multi-dimensional phylogenetic analyses, widely accepted genome-wide ANI/AAI thresholds) and SeqCode rules, we formally propose two novel taxa: Parviradicicola hetaonensis gen. nov., sp. nov. (type material: txb011_bin.8.strictTS) and Parviputeicola dengkouensis gen. nov., sp. nov. (type material: sgl022_bin.19.origTS), plus two novel families and one novel order. We further identified potential drivers and important associations related to Ca. Saccharimonadia genome size evolution and adaptive metabolic traits. This work refines the Ca. Saccharimonadia taxonomic framework, providing critical genomic references for follow-up research.