The taxonomic position of two lactic-acid-producing bacterial strains, isolated from wheat sourdough in South Korea, was studied using a polyphasic approach. Phylogenetic analysis on the basis of 16S rRNA gene sequences and biochemical and physiological characteristics indicated these two strains to be members of the genus Lactobacillus. They had high 16S rRNA gene sequence similarity (98.5 %) with Lactobacillus rossiae DSM 15814(T) and very low (<94.0 %) similarity with any other recognized species of the genus Lactobacillus. These two strains (designated M1-212(T) and M2-236) were heterofermentative, facultatively anaerobic, Gram-positive, non-spore-forming, non-motile, short rod-shaped bacteria. The optimum growth temperature for these strains was 30 degrees C (no growth at 15 or 45 degrees C) and they were able to tolerate 5 % (w/v) NaCl. The G+C content of the genomic DNA of the two strains was 45.5 mol%, within the range of values reported for the genus Lactobacillus (32-53 mol%). The peptidoglycan was of the A3alpha (l-lys-d-glu-l-Ala) type. Physiological, biochemical and genotypic data, as well as results of DNA-DNA hybridization of the genomic DNA with one of the closest phylogenetic relatives, L. rossiae DSM 15814(T), indicated that the strains represent a novel species of the genus Lactobacillus, for which the name Lactobacillus siliginis sp. nov. is proposed. The type strain is M1-212(T) (=KCTC 3985(T)=NBRC 101315(T)).