Functions Of Motile-related Genes In Vibrio Harveyi

Vibriosis is a kind of bacteriosis widely spreading on the earth.Vibrio harveyi is a vital pathogen in aquaculture,which is severely harmful to wild fish,custacea,shellfish and other animals of aquaculture.Therefore,the pathogenic mechanism of V.harveyi was paid much attention in recent years.The present research showed that the pathogenic mechanism of V.harveyi was related to ECP(Extracellular Product),hemolysin and so on,while there has been not any report on motility and the role of motility on the early stage of infection of this bacterium.As the important role of motility in infection of bacterial,motile-related genes of V. harveyi was identified and function of these genes were characterized in the present study,in order to reveal the relationship between motility and pathogenicity.we wish it could provide us Rationale of Pathogenicity and Prevention of V.harveyi.The results of this study provided further understanding of the pathogenic mechanism of V.harveyi.The suicide plasmid pLOFKm,carring a transposon mini-Tn10,was transferred to the recipient V.harveyi to generate an insertional mutant library by cell conjugation between the donor Escherichia coli Sm10 (pLOFKm) and the recipient V.harveyi TS-628 by filter mating.More than tow thousand individual insertion transposon mutants were screened and three mutants exhibited defective in motility.465bp sequence of mutant H1 flanking transposon showed the highest identity (96.9%) to a hypothetical protein gene of V.harveyi ATCC BAA-1116 at genome position 3612978 to 3613443 and the second-highest identity (91.8%) to the pgk gene of V.parahaemolyticus RIMD 2210633.To the H2,356bp flanking sequence showed the highest identity (94.6%) to a hypothetical protein gene of V.harveyi ATCC BAA-1116 at genome position 3203663 to 3204019 and the second-highest identity (92.4%) to the flaB gene of V.alginolyticus HY9901.The biological characteristics of the mutants including growth,chemotactic,early stage of adhesion,biofilm formation were determined . The results displayed that the growth characteristics of H1 are abviously different from the wild type strain and the growth parameters of H2 and H3 were similar with those of the wild type strain.Chemotactic testing showed that all the three mutants were greatly impaired in chemotaxis.The study on the early stage of adhesion of the wild type strain and the three mutants reveal that the wild type strain exhibited the strongest adhesion ability and all the mutants exhibited weaker adhesion ability.The biofilm formation assay revealed that the wild type strain produced the greatest biofilm and the mutant H2 produced the minimal biofilm.Hence, the target gene in H1 and H2 were first identified to be the motile-related genes in V. harveyi in this study and their function is similar with the pgk gene and flaB gene respectively.