Cultivation And Pathogen Inhibition Of Massive Coral Associated Bacteria

Disease is one of the major causes of coral reef degradation,and the impact intensity and scope of these diseases continue to increase.Previous studies have shown that:(1)massive corals have strong environmental adaptability;(2)microorganisms play an important role in maintaining coral health,but the specific mechanism of action is still unclear.Therefore,this thesis,taking Porites sp.,Platygyra sp.and Favia sp.as the research objects,conducts pure culture and disease resistance research on their symbiotic bacteria to understand the role and mode of action of symphytic bacteria in coral health.The results and conclusions are as follows:First of all,in the research a total of 737 strains of pure culture bacteria were obtained,including 472 strains of Porites sp.,202 strains of Platygyra sp.and 63 strains of Favia sp.,which are subordinate to 5 phyla,7 classes,19 orders,37 families,and 101 genera.Among them,potential probiotics Ruegeria and Pseudoalteromonas accounted for the most in number.And some potential pathogenic bacteria such as Vibrio coralliilyticus and Vibrio shilonii were also obtained.Secondly,the research had a laboratory activity screening on the pure cultured bacteria obtained above with opportunistic pathogen Vibrio coralliilyticus and Vibrio shilonii as indicator bacteria,and a total of 29 strains with antibacterial activity were screened out,of which 27 strains belonged to Pseudoalteromonas.The study on the antagonistic relationship between 22 strains with relatively stable activity and two strains of pathogenic bacteria found that it is more difficult to inhibit pathogenic bacteria under high temperature and oligotrophic conditions.And co-culture experiments of anti-pathogenic bacteria and pathogenic bacteria found that there were individual differences influenced by nutrition in the inhibition ability of bacteria to pathogenic bacteria,which indicates that the balance between bacteria in the natural environment is complex.Thirdly,the research conducted fermentation,extraction,purification and identification of the active substances on Pseudoalteromonas sp.327 with better activity.And a comparation of UV-Vis absorption spectrum and mass spectrum showed that the antimicrobial substance of strain 327 was quinolinol homologues,which are(1)2-heptyl-4-quinolinol;(2)2-hexyl-4-quinolinol;(3)2-pentyl-4-quinolinol,etc.In summary,through pure culture and analysis of active substances,this thesis draw the following conclusions:culturable symbiotic bacteria in massive coral are rich in diversity;the probiotics and opportunistic pathogens coexist and balance each other;The inhibition of pathogenic bacteria is more difficult under high temperature and oligotrophic conditions;the balance between bacteria in natural environment present complexity;the active substance of strain 327 are homologues of hydroxyquinoline;Probiotics may protect coral health by secreting antibiotics to inhibit the growth of pathogenic bacteria.