Two bacterial strains, designated GH34-4(T) and GH41-7(T), were isolated from greenhouse soil cultivated with cucumber. The bacteria were strictly aerobic, Gram-negative, rod-shaped and oxidase- and catalase-positive. 16S rRNA gene sequence analysis indicated that these strains belong to the genus Lysobacter within the Gammaproteobacteria. Strain GH34-4(T) showed highest sequence similarity to Lysobacter yangpyeongensis GH19-3(T) (97.5 %) and Lysobacter koreensis Dae16(T) (96.4 %), and strain GH41-7(T) showed highest sequence similarity to Lysobacter antibioticus DSM 2044(T) (97.5 %), Lysobacter enzymogenes DSM 2043(T) (97.5 %) and Lysobacter gummosus ATCC 29489(T) (97.4 %). Levels of DNA-DNA relatedness indicated that strains GH34-4(T) and GH41-7(T) represented species clearly different from L. yangpyeongensis, L. antibioticus, L. enzymogenes and L. gummosus. The major cellular fatty acids of strains GH34-4(T) and GH41-7(T) were iso-C(16 : 0), iso-C(15 : 0) and iso-C(17 : 1)omega9c, and the major isoprenoid quinone was Q-8. The DNA G+C contents of GH34-4(T) and GH41-7(T) were 62.5 and 66.6 mol%, respectively. On the basis of the polyphasic taxonomic data presented, it is evident that each of these strains represents a novel species of the genus Lysobacter, for which the names Lysobacter niabensis sp. nov. (type strain GH34-4(T)=KACC 11587(T)=DSM 18244(T)) and Lysobacter niastensis sp. nov. (type strain GH41-7(T)=KACC 11588(T)=DSM 18481(T)) are proposed.