Strain PB-6250T, isolated from soil in Japan, was first identified in 1992. In contrast to its original taxonomic classification, its 16S rRNA gene sequence showed the highest similarity (99.2 %) to the sequence of Lysobacter enzymogenes DSM 2043T, with Lysobacter antibioticus DSM 2044T being the next most closely related species (98.7 %) with a validly published name. Chemotaxonomic data (fatty acid profile, quinone and polar lipid composition) and the G+C content of strain PB-6250T were compared with those of the closely related type strains L. enzymogenes LMG 8762T, L. antibioticus LMG 8760T, L. capsici DSM 19286T and L. gummosus LMG 8763T; this supported the affiliation of strain PB-6250T to the genus Lysobacter. Phylogenetic analyses, DNA-DNA-hybridization data, biochemical and physiological characteristics strongly supported the genotypic and phenotypic differentiation of strain PB-6250T from species of Lysobacter with validly published names. Strain PB-6250T, therefore represents a novel species, for which the name Lysobacter firmicutimachus sp. nov. is proposed. The type strain is PB-6250T (=LMG 28994T=DSM 102073T).