Microbiological Study And Quorum Sensing Research Of Reared Stichopus Japonica Suffers From A Kind Of Skin Ulceration Disease

Along with the domestic rearing industry of Stichopus japonica rapidly expand, a series of diseases are booming, which bring severe economic loss. Reared Stichopus japonica in China suffers from a kind of skin ulceration disease, which has higher mortality rate and infectivity, become to be the research focus. The infection involves a head shaking and viscera expelling at early time, and is followed with mouth and cloacal opening tumidity, then the body of the diseased individuals will be shrinking and rigidity together with white or blue lesion spots on the body wall. In the later period, these small lesion spots grow more and bigger to large ulceration and finally cause the death of individuals. This disease can often cause all individuals reared in the same pool die in a very short time. And the pathogens are supposed to be bacterial by most researchers. However, the relevant research has in the primary stage at present, for the diseases was random occurrence and much more environmental factors which led it is more difficult to solve.In order to study the pathogenesis and the Quorum sensing research of reared Stichopus japonica suffers from a kind of skin ulceration disease, this article takes the reared Stichopus japonica from Qingdao as the material, separate 7 strains: C6, 4, TB, BP2, BP3, BP4 and BP6. The physics and chemistry research indicated that these strains grow rapidly: after 22 hours, C6 grows in its platform stage, 4, BP4 and BP6 need 19 hours, and then, TB, BP2 and BP3 only need 13 hours. The best cultivate conditions are: Salinity 33-36‰, temperature about 32℃, pH value about7~ 8. The antibiotic sensitive experiments show that these bacterium strains have widespread resistance on Chloromycetin, Trimethoprim and sulphame-thoxazole, Erythromycin, Gentamycin, Fluperacid and so on. In the API-20E experiments, arginine double hydrolytic enzyme, lysine decarboxylase, ornithine decarboxylase, urease, tryptophan deaminase and 3- hydroxy-butanone enzymes are the positive reactions.Through research on the extraction, purification, appraisal and so on of the 7 strains' quorum sensing auto-inducer, it is indicated that the auto-inducers of the 7 strains are really existed, but have the low quantity and show the sharp contrast with the positive control. The molecular structure of AHLs is connected by invariable acetazolamide chain and stable L-homoserine lactones. This structure is more stable under the acidic condition and strong base will led the L-homoserine lactones split-ring, then destroy its structure. The experiments indicated that the activeness of the 7 strains' quorum sensing auto-inducers and the culture medium pH value change basically is in reverse proportion. So it can be believed that in the higher pH value liquid will possibly cause the auto-inducer breakdown to reduce its activeness. According to the correlation data, transplants the eelgrass may reduce the disease morbidity. It seems that there is a promising alternative for antibiotics in fighting bacterial infections by using techniques that disrupt quorum sensing systems of pathogenic bacteria. This new approach might also have value in aquaculture since a link between quorum sensing and virulence factor expression in several aquatic pathogens has been demonstrated. Although the datas about the impact of quorum sensing on virulence of aquatic pathogens are still lacking, fundamental research in the quorum sensing's domain will provide much more information to help people find the directed search for antagonists.