Two bacterial strains, designated GH34-4T and GH41-7T, 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 GH34-4T showed highest sequence similarity to Lysobacter yangpyeongensis GH19-3T (97.5 %) and Lysobacter koreensis Dae16T (96.4 %), and strain GH41-7T showed highest sequence similarity to Lysobacter antibioticus DSM 2044T (97.5 %), Lysobacter enzymogenes DSM 2043T (97.5 %) and Lysobacter gummosus ATCC 29489T (97.4 %). Levels of DNA–DNA relatedness indicated that strains GH34-4T and GH41-7T represented species clearly different from L. yangpyeongensis, L. antibioticus, L. enzymogenes and L. gummosus. The major cellular fatty acids of strains GH34-4T and GH41-7T were iso-C16 : 0, iso-C15 : 0 and iso-C17 : 1 ω9c, and the major isoprenoid quinone was Q-8. The DNA G+C contents of GH34-4T and GH41-7T 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 GH34-4T=KACC 11587T=DSM 18244T) and Lysobacter niastensis sp. nov. (type strain GH41-7T=KACC 11588T=DSM 18481T) are proposed.