Abstract:［Objective］To cultivate various yet-to-be cultured heterotrophs from anaerobic granule sludge，we used a selective culture medium with low concentrations of substrates supplemented a variety of antibiotics.［Methods］An obligate anaerobic，thermophilic，hydrogen-producing bacterium，strainVM20-7T，was isolated from an upflow anaerobic sludge blanket ( UASB) reactor treating high-strength organic wastewater from isomerized sugar production processes．［Results］Cells of strain VM20-7T are non-motile，spherical，pear or teardrop shaped，occurring singlyo r as aggregates (0.7－2.0μm×0.7－2.0μm)．Spore formation was not observed． Growth temperature ranges from 35－50℃ (optimum 45℃)，pH ranges from 6.0－8.3 (optimum 7.0－7.5)，NaCl tolerant concentration ranges from 0%－0.5% (w/v，optimum 0%)．Nitrate，sulfate，thiosulfate，sulfite，elemental sulfur and Fe (III)-NTA were not used as terminal electron acceptors． Strain VM20-7T utilizes a wide range of carbohydrates，including glucose，maltose，ribose，xylose， sucrose，galactose，mannose，raffinose，pectin，yeast extract and xylan． Acetate and H2 are the main end products of glucose fermentation． The G+C content of the genomic DNA was 60.9 mol%．16S rRNA gene sequence analysis revealed that it is related to the Pirellula-Rhodopirellula-Blastopirellula ( PRB) clade within the order Planctomycetales (82.7－84.3% similarity with 16S rRNA genes of other known related species)．［Conclusion］ The first obligate anaerobic bacterium within the phylum Planctomycetes was isolated with low concentration of carbohydrates and antibiotics．On the basis of the physiological and phylogenetic data，the name Thermopirellula anaerolimosa gen．nov.，sp. nov．is proposed for strain VM20-7T (= CGMCC 1. 5169T = JCM 17478T = DSM 24165T)．