A thermo-acidophilic bacterium, designated strain ACK006T,was isolated from the soil of a hot spring at Tengchong inChina. Cells were Gram-staining-positive, motile, catalasepositiveand oxidase-negative, spore-forming rods. The isolategrew aerobically at 30–50°C (optimum at 45°C), pH2.0–6.0 (optimum pH 3.2) and 0–5.0% (w/v) NaCl (optimum1% NaCl). Phylogenetic analyses based on 16S rRNA genesequences indicated that strain ACK006T belongs to the genusAlicyclobacillus with the sequence similarity of 92.3,92.4, 92.5, and 92.8% to Alicyclobacillus cycloheptanicusSCHT, Alicyclobacillus ferrooxydans TC-34T, Alicyclobacilluscontaminans 3-A191T and Alicyclobacillus disulfidooxidansSD-11T, respectively. Similarity to other species of the genusAlicyclobacillus was 90.3–92.8% and similarity to species ofthe genus Tumebacillus was 85.9–87.8%. The genomic DNAG+C content was 53.7 mol%. The predominant menaquinonewas MK-7. Major fatty acids were ω-cycloheptane C18:0,iso-C17:0 and anteiso-C17:0. The cell-wall peptidoglycan wasthe A1γ type; containing meso-diaminopimelic acid as thediagnostic diamino acid. On the basis of polyphasic analysisfrom this study, strain ACK006T represents a novel speciesof the genus Alicyclobacillus for which the name Alicyclobacillustengchongensis sp. nov. is proposed. The type strain is ACK006T (=KCTC 33022T =DSM 25924T).