Two Gram-positive, moderately thermophilic, endospore-forming, rod-shaped, motile bacteria, designated PDF25(T) and PDF30, were isolated from Karakoc hot spring in the province of Izmir, Turkey, and were characterized in order to determine their phylogenetic positions. 16S rRNA gene sequence analysis revealed that the two strains belonged to the genus Brevibacillus; strain PDF25(T) showed highest sequence similarity to strain PDF30 (99.40/) and Brevibacillus thermoruber DSM 7064(T) (98.5 %). The major fatty acids of strain PDF25(T) were iso-C-15:0 (39.30%), anteiso-C-15:0 (26.10%) and iso-C-16:0 (14.75%). Polar lipid analysis revealed diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmonomethylethanolamine, phosphatidylethanolamine, and a variety of unidentified aminophospholipids, phospholipids and aminolipids. The major isoprenoid quinone was MK-7. The G + C content of the genomic DNA was 56.09 mol%. DNA DNA hybridization experiments revealed 58% relatedness between strain PDF25(T) and B. thermoruber DSM 7064(T). Based on these data, the two strains are considered to represent a novel species of the genus Brevibacillus, for which the name Brevibacillus aydinogluensis sp. nov. is proposed. The type strain is PDF25(T) (=DSM 24395(T)=LMG 26289(T)).