Phylum Planctomycetota is a large and widespread group of prokaryotes with a number of unusual structural properties. They play an important role in global carbon and nitrogen cycles and are of biotechnological relevance (Kallscheuer and Jogler, 2021; Peeters and van Niftrik, 2019; Wiegand et al., 2018). At present, all taxonomically described planctomycetes with validly published names belong to two recognized classes, namely the Planctomycetia and Phycisphaerae (Fukunaga et al., 2009; Ward, 2010), which accommodate aerobic and anaerobic chemoorganotrophic planctomycetes. DNA sequences of Phycisphaerae occur in many genomic datasets obtained from a wide variety of environments. Despite their ubiquitous distribution, only few species have been brought into culture. Currently, the class Phycisphaerae is subdivided into the orders Phycisphaerales (Fukunaga et al., 2009), Tepidisphaerales (Kovaleva et al., 2015) and Sedimentisphaerales (Spring et al., 2018). The order Sedimentisphaerales represented by strictly fermentative mesophilic anaerobes and includes three families: Anaerobacaceae, Anaerohalosphaeraceae and Sedimentisphaeraceae, which accommodate five cultured and taxonomically described species (Khomyakova et al., 2024; Pradel et al., 2020; Spring et al., 2018).

A culture-independent studies have shown that the Sedimentisphaerales is found predominantly in sulfur or methane-rich anoxic marine sediments, hypersaline lakes, or deep sea habitats (Hamdan et al., 2018; Spring et al., 2018). Sedimentisphaerales are known as mesophilic fermentative polysaccharides degraders, and microorganisms of the families Sedimentisphaeraceae and Anaerobacaceae appear to be capable of breaking down more polysaccharides than the Anaerohalosphaeraceae (Khomyakova et al., 2024; Klimek et al., 2024), represented to date by a single cultivated species – Anaerohalosphaera lusitana (Pradel et al., 2020). Genomic data indicates that most Anaerohalosphaeraceae are capable of nitrate, sulfate, and sulfite reduction (Lenferink et al., 2024), but only sulfate assimilation was verified experimentally in Anaerohalosphaera lusitana and nitrate could not be reduced under the tested conditions (Pradel et al., 2020). Another feature characteristic of representatives of the order Sedimentisphaerales is their dependence on the presence of sodium chloride ions: almost all described species are moderately halophilic and NaCl is necessary for their growth (Khomyakova et al., 2024; Pradel et al., 2020; Spring et al., 2018).

Thermal ecosystems in Uzbekistan remain poorly characterized (Slobodkina et al., 2025). Such habitats are of great scientific interest due to their diverse microbial communities that thrive under conditions of high temperature and often low oxygen. Thermophilic microorganisms inhabiting such ecosystems may have important evolutionary and biotechnological significance.

Here we describe a novel anaerobic non-halophilic thermotolerant strain U12dextrT, belonging to Anaerohalosphaeraceae family, isolated from a thermal water stream in Uzbekistan, that extends the known genomic and phenotypic diversity within the class Phycisphaerae.