| Vibrio exhibiting high toxicity,rapid disease rate,infecting a variety of hosts,and strong drug resistance,is one of the most important bacterial pathogens in the mariculture system,such as Vibrio harvei,Vibrio parahaemolyticus,Vibrio alginolyticus,Vibrio campbelliii,and Vibrio Owen,causing huge economic losses to the mariculture industry,which has become one of the major bottlenecks restricting the green development of mariculture industry.Additionally,Xisha Sea with the unique tropical climatic conditions and geographical location contains a large amount of unique microbial resources,and it has a prominent advantage of resource endowment to develop tropical probiotics for aquaculture.In this study,all samples were collected from four habitats in Xisha Sea area,sediments,water bodies,corals,and halobios.By microbial culturable technology combined with the filter paper method experiment,the distribution and antagonistic capability of culturable microorganisms and antagonists against five main Vibrio in Xisha Sea were comprehensively analyzed,and the contribution of representative environmental factors to the distribution of culturable microorganisms and antagonists was investigated.The main results are as follows:(1)Distribution of culturable microorganisms in Xisha Sea area:In this study,1,325 strains of culturable bacteria were isolated and identified from four habitats in Xisha Sea,including sediment,surface seawater,coral,and halobios(Echinoidea,Holothuria,Actiniaria,Phylum Porifera,Asteroidea,and Alage),belonging to 4 phyla and 34 genera,including Proteobacteria(96.76%),Firmicutes(2.79%),Actinomyces(0.15%),and Bacteroides(0.30%).Vibrio(68.93%)was the dominant genus,followed by Pseudomonas(9.35%),Alteromonas(4.90%),and Halomonas(3.925%),which displayed the habitat dependence distribution.In details,294 strains isolated from coral belonged to 4 phyla of Proteobacteria(95.58%),actinomyces(0.33%),Firmicutes(3.76%),and Bacteroides(0.33%),199 strains isolated from sediments belonged to Proteobacteria(97.99%)and Firmicutes(2.01%),295 strains isolated from halobios belonged to Proteobacteria(95.25%),Actinomyces(2.03%),Firmicutes(2.03%),and Bacteroides(0.69%),while 537 strains isolated from seawater belonged to Proteobacteria(96.46%),Actinomyces(0.37%),Firmicutes(2.98%),and Bacteroides(0.19%).(2)Antagonistic capability of the antagonists against Vibrio:A total of 227 antagonists against V.harvei,V.parahaemolyticus,V.alginolyticus,V.campbelliii,and V.Owen,were screened from 1,325 culturable bacteria,which belonged to4 phyla and 17 genera,including Proteobacteria(93.39%),Firmicutes(4.85%),Actinomyces(0.88%),and Bacteroides(0.88%),while Vibrio(58.59%)genus was the dominant.In details,32 antagonists isolated from coral belonged to 4 phyla of Proteobacteria(81.25%),Firmicutes(18.75%),25 strains isolated from sediments belonged to Proteobacteria,39 strains isolated from halobios belonged to Proteobacteria(89.74%),Actinomyces(5.28%),and Bacteroides(5.28%),while 131 strains isolated from seawater belonged to Proteobacteria(96.18%),Firmicutes(3.82%),and Bacteroides(0.19%).Of which,216 antagonistic strains against V.campbelliii,201 antagonistic strains against V.Owen,165 antagonistic strains against V.harvei,213 antagonistic strains against V.parahaemolyticus,and 184 antagonistic strains against V.alginolyticus were screened.It’s worth noting that 138 antagonistic strains can against 5 types of pathogenic Vibrio,whereas only 3 strains respectively can against only 1 type of these.(3)Quantitation of the capability of the antagonistsBy measuring the diameter of the inhibition zone on the Vibrio indicators plates,the antagonists with the relatively high inhibition zone were quantitated.According to the results,Halomonas sp.PC18 from the coral habitat displayed the highest V.Owen inhibition zone of 6.03 mm,Shewanella sp.PF34 from the halobios habitat displayed the highest V.harvei inhibition zone of 7.23 mm,Pseudoalteromonas sp.PS197 from the sediment habitat displayed the highest V.Owen inhibition zone of 6.10 mm,and Alteromonas sp.PW156 from the seawater habitat displayed the highest V.harvei inhibition zone of 11.03 mm.Additionally,25 strains with a diameter of V.campbelliii inhibition zone more than 4 mm(maximum,Vibrio sp.PC241: 5.07 mm),41 strains with a diameter of V.owensii inhibition zone more than 4 mm(maximum,Pseudomonas sp.PW283: 7.10 mm),20 strains with a diameter of V.harveyi inhibition zone more than 4mm(maximum,Alteromonas sp.PW156: 11.03 mm),17 strains with a diameter of V.parahaemolyticus inhibition zone more than 4 mm(maximum,Alteromonas sp.PW156:5.08 mm),and 19 strains with a diameter of V.alginolyticus inhibition zone more than 4mm(maximum,Vibrio sp.PW164: 6.73 mm)were identified.(4)Correlation analysis of the relationship of environmental factors and distribution of culturable microorganisms and their antagonistsTo further analyze the relationship between environmental factors and the distri bution of culturable microorganisms and their antagonistic communities in Xisha Se a area.In this work,the correlation between "environmental factor-culturable microo rganism" and "environmental factor-antagonistic strain" was analyzed respectively in different habits.The results showed that total inorganic nitrogen,temperature,dissol ved oxygen,COD,total phosphorus,and phosphate as the main factors had signific ant effects on the distribution of the 9 culturable bacterial genera,including Pseudo alteromonas,Pseudovibrio,Vibrio,Halomonas,Photobacterium,Bacillus,Pseudomon as,Tenacibaculum,Exiguobacterium,while temperature,COD,and total phosphorus as the main factors had significant effects on the distribution of the Vibrio antagoni stic genera,including Photobacterium,Idiomarina,and Acinetobacter.In brief,Xisha Sea embraces extremely rich culturable bacteria and antagonistic bacteria,which displays a habitat-dependent distribution feature and high correlation with environmental factors.This work will facilitate the development and utilization of microbial resources from Xisha region... |
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