Taxonomic and metabolic diversity of microbial communities in a thermal water stream in Uzbekistan and proposal of two new classes of uncultivated bacteria, Desulfocorpusculia class. nov. and Tepidihabitantia class. nov., named following the rules of SeqCode

Thermal ecosystems in Uzbekistan remain poorly characterized, particularly through culture-independent approaches. In this study, we performed 16S rRNA gene metabarcoding and metagenomic sequencing of microbial communities from a hot stream formed by the discharge of thermal artesian groundwater in the Navoiy region. The taxonomic composition of microbial communities varied with temperature and sample type, with the phylum Chloroflexota abundant in most samples. Members of Aquificota, Deinococcota, and Thermotogota dominated in sediments with temperatures around 60 °C, while Desulfobacterota and Cyanobacteriota were more abundant at lower temperatures. Metagenomic sequencing of the microbial community in sediment under orange-brown mat (54 °C) revealed a dominance of the phyla Chloroflexota, Armatimonadota, Aquificota, Ignavibacteriota, Desulfobacterota and Bacteroidota. Metagenomic data indicated that fermentation, aerobic degradation of organic matter, hydrogen oxidation, and sulfur cycling are the main metabolic processes. Two high-quality metagenome-assembled genomes (MAGs) were described as novel taxa named following the rules of SeqCode. Genome analysis suggests that both organisms are heterotrophic anaerobes capable of sulfate reduction or fermentation. We provide the description of Desulfocorpusculum asiaticum^Ts gen. nov., sp. nov. affiliated with the novel family Desulfocorpusculaceae fam. nov., order Desulfocorpusculales ord. nov. and class Desulfocorpusculia class. nov.; and the description of the new species and genus Tepidihabitans asiaticus^Ts gen. nov., sp. nov. affiliated with the novel family Tepidihabitantaceae fam. nov., order Tepidihabitantales ord. nov. and class Tepidihabitantia class. nov.