Function Of Chitinase In Lysobacter Enzymogenes OH11

Control of plant diseases is very important key problem in agricultural production. Many diseases control mainly depended on the chemical pesticide. Using too many chemical pesticide had resulted in pollution to environment and harm to human beings and animals. Meanwhile, it had induced the resistance of pathogens to pesticide. However, biocontrol is safe to human beings and animals. It also has little polution to enviroment. Therefor, biocontrol has been focused in recent years.Lysobacter enzymogenes OH11, screened and isolated from the rhizosphere soil of pepper, is a new biocontrol bacterial strain. It produces a variety of extracellular enzymes including chitinase, glucanase, protease and cellulase and has the ability to inhibit many pathogens of plant diseases.It has a bright future in the application of biological control.Chintin is an important component of fungi cell wall. OH 11 secrets chintinase which could hydrolyze chitin, and then breaked the cell wall of fungi. Therefor, chitinase may be related to the function of biocontrol.According to the squence of genomic DNA and chiA, we constructed a plasmid used for chiA deletion. Through double exchange, we got the mutantΔchiA which lost chiA. The detection on the chitin flats showed that mutantΔchiA was no longer degrading chitin, while the wild type OH11 could.Southern blot is a classific method for verifing the number of copies of a given gene and the deletion mutant. We used a 605bp segment of chiA as the probe, and cut the genome DNA of wild OH 11 with enzymes EcoRⅠand HindⅢ, and then we comfirmed that chiA existed in OH 11 just with one copy. Also we used a 518bp segment downstream of chiA as the probe, and cut the genome DNA of wild OH 11 and mutantΔchiA with enzymes EcoRⅠand HindⅢ, then we verified that mutantΔchiA was the mutant lost chiA.In order to comfirm the function of chiA attributed to biocontrol of OH11, we researched the antibacterial ability ofΔchiA and wild OH11. The results showed that there was no difference betweenΔchiA and wild OH11 about the ability to inhibit pathogens. We could conclude that chiA was not the key factor for the biocontrol of OH11.