A novel moderately thermophilic, Gram-positive, endospore-forming, rod-shaped, motile bacteria and alkaline active xylanase producing strain D1021T, was isolated from Kaynarca hot spring in the province of Izmir, Turkey and was characterized in order to determine its phylogenetic position. Growth was observed at 3570 degrees C (optimum 60 degrees C), at pH 6.010.0 (optimum pH 7.0). The strain D1021T grew on a wide range of carbon sources including ribose, xylose, glucose, maltose, sucrose, arabinose, and melibiose. The major isoprenoid quinone was MK-7. 16S rRNA gene sequence analysis showed that strain D1021T is related to members of genus Anoxybacillus, with similarities to Anoxybacillus spp. varying from 94.7 to 98.7. The major fatty acids of strain D1021T were iso-C15:0 (57.46%) and iso-C17:0 (13.98%). The DNA G+C content was 42.9mol %. DNADNA relatedness values between Anoxybacillus spp. and D1021T were lower than 70%. On the basis of phenotypic characteristics, rpoB analysis, phylogenetic and DNADNA hybridization data, it was proposed that the strain D1021T (=DSM 21706T=LMG 25303T) should be placed in the genus Anoxybacillus as the type strain of a novel species, Anoxybacillus kaynarcensis sp. nov. The GenBank accession number for the 16S rRNA sequence is EU926955.