The taxonomic positions of Lysobacter species with validly published names and a novel strain Ko07(T), which was newly isolated from an upflow anaerobic sludge blanket reactor treating wastewater from a brewery, were (re)estimated on the basis of results obtained by using a polyphasic taxonomy approach. Phylogenetic inference based on 16S rRNA gene sequences showed that strain Ko07(T) and all Lysobacter species with validly published names clustered together in a phylogenetic branch within the class 'Gammaproteobacteria'. The sequence similarity of strain Ko07(T) to the type strains of established Lysobacter species was in the range 94.9-96.7 %. Ubiquinone Q-8 and branched fatty acids, C(11 : 0) iso, C(15 : 0) iso, C(16 : 0) iso, iso C(17 : 1)omega9c and C(11 : 0) iso 3OH, predominantly appeared in strain Ko07(T) as well as in all type strains of the recognized Lysobacter species. The DNA-DNA hybridization values of strain Ko07(T) with those of recognized Lysobacter species were estimated to be 2-20 %. Despite sharing common taxonomic features in important phenotypic characteristics, such as gliding movement, long-rod shape and proteolytic activity, strain Ko07(T) could be distinguished from the Lysobacter species with validly published names by its low DNA-DNA hybridization value, a comparatively low DNA G + C content (63.8 mol%), substrate utilization and some physiochemical characteristics. On the basis of the results obtained in this study, it is proposed that strain Ko07(T) should be classified as representing a novel member of the genus Lysobacter, for which the name Lysobacter concretionis sp. nov. is proposed. The type strain is Ko07(T) (=KCTC 12205(T) = DSM 16239(T)).