Abstract: The mutant library of Lysobacter enzymogenes strain OH11 was successfully constructed by mating mariner transposon into strain OH11. One mutant D-11, which reduced the activities of several lytic enzymes, including α-lytic protease, cellulase, chitinase and β-1,3-glucanase, was selected from over 5000 chloramphenicol-resistant (Cm\+r) mutants. The transposon insertion site was identified as a ctp gene by subclone strategy. Sequence analysis showed that the gene was 2214 bp with a 69% G+C content. The OH11 ctp homology analysis indicated that the homology between OH11 and Stenotrophomonas maltophilia strain was 79%, and that between OH11 and Xanthomonas campetris strain was 78%. A ctp deletion mutant Δctp was constructed by homologue recombination technology. Phenotype analysis revealed that Δctp had the same growth rate as that of wild-type OH11 in both nutrient-rich medium (2YT) and nutrient-deficient medium (MMX). Compared with wild-type OH11, Δctp significantly reduced production of three-type lytic enzymes, i.e. α-lytic protease, cellulase and β-1, 3-glucanase, but had the wild-type ability in chitinase production, and Δctp also showed an obvious reduction of biofilm formation. However, Δctp displayed wild-type antimicrobial activity against Sclerotinia sclerotiorum, Rhizoctonia solani and Phytophthora capsici. All phenotypes of mutant were restored in complemented strain.