Abstract: The class Thermoleophilia represents a deep-branching lineage within the phylum Actinomycetota, yet its taxonomic diversity remains incompletely resolved due to the limited availability of cultured representatives and uneven integration of genome-resolved diversity. Here, we performed an integrative phylogenomic and taxonomic analysis of Thermoleophilia using three newly generated genomes derived from desert soils in Xinjiang, China, including two cultured isolate genomes and one metagenome-assembled genome (MAG), together with publicly available MAGs. Phylogenomic reconstruction based on conserved marker genes, overall genome relatedness indices (OGRI), and 16S rRNA gene sequences revealed several well-supported lineages that expand the currently characterized diversity within the order Solirubrobacterales. Strain SYSU D00693^T represents a novel family, genus, and species, for which the names Vescideserticolaceae fam. nov., Vescideserticola gen. nov., and Vescideserticola fastidiosus sp. nov. are proposed. Strain SYSU D01012^T represents a novel species within the genus Patulibacter, designated Patulibacter desertihabitans sp. nov. Genome-based analyses further demonstrated that BS_bin.015, together with BP_457 and BP_458, forms a distinct lineage corresponding to the GTDB placeholder genus AC-38. Phylogenomic and comparative genomic evidence supports the proposal of Candidatus Sabulibiaceae fam. nov. and Candidatus Sabulibium gen. nov., comprising three candidate species-level lineages. Comparative genomic analyses further revealed lineage-associated variation in genomic functional potential among the analyzed genomes. Collectively, this study expands the currently characterized taxonomic diversity of Thermoleophilia and provides genomic insights into the diversity and evolutionary relationships of this underexplored bacterial class.

Key words: metagenome-assembled genome, novel taxa, phylogenomics, polyphasic taxonomy, Solirubrobacterales, Thermoleophilia