Biodiversity Of Culturable Bacteria Associated With Crassostrea Hongkongensis From The Tidal Flat Of Naozhou Island

To understand the diversity of culturable bacteria isolated from a oyster(Crassostrea hongkongensis) collected from the coastal sea water area of NaozhouIsland (20°52′N～20°56′N110°33′E～110°38′E) in the Leizhou Bay onSouth China Sea, bacteria were isolated by using conventional culture-dependentmethod and investigated by means of phylogenetic analysis based on16S rRNA genesequence comparisons. And the antimicrobial activities of the fermentation brothextracts from the isolates were detected on8sensitive microorganisms in order to findsome isolates exhibiting strong bioactivity to be further used in exploitation.102bacteria were isolated strains from the sample on media [MA (marine agar2216), MH (moderate halophilic medium agar), NA (nutrient agar)] supplemented with0–25%(w/v)NaCl. Preliminary observation of the isolations strains and screening bycolony morphology, microstructure morphology, results of gramstain and physiologyand biochemistry characters. phylogenetic diversity analysis of74representative strains,picking out of102isolation strains, by16S rRNA gene sequences. The results showedthat74isolates were members of18genera (Idiomarina, Morganella, Proteus,Halomonas, Paracoccus, Wohlfahrtiimonas, Marinobacter, Vibrio, Pseudoalteromonas,Shewanella, Oceanimonas, Nitratireductor, Myroides, Bacillus, Virgibacillus,Staphylococcus, Enterococcus, Trichococcus) of16families (Idiomarinaceae,Enterobacteriaceae, Halomonadaceae, Rhodobacteraceae, Xanthomonadaceae,Alteromonadaceae, Vibrionaceae, Pseudoalteromonadaceae, Shewanellaceae,Aeromonadaceae, Phyllobacteriaceae, Flavobacteriaceae, Bacillaceae,Staphylococcaceae, Enterococcaceae, Carnobacteriaceae) in4phylogenetic groups(Gamma-Proteobacteria, Alpha-Proteobacteria, Bacteroidetes, Firmicutes). The most ofisolates were within the subphylum Gamma-Proteobacteria (45strains,60.8%),followed by Firmicutes (12strains,16.2%), Bacteriodetes (11strains,14.9%) andAlpha-Proteobacteria (6strains,8.1%). can be grouped into38species, Thephylogenetic relationship among the isolation strains and the laterly known strains hadthe significant genetic diversity of phylogenetic relationship(the similarly between94.3%–99.8%) in16S rRNA gene sequences. out of74isolates at least six JSM strains(111020,111039,111069,111072,111085,111090) could represent potential new taxa.Strain JSM111069could represent a novel genus in the family Carnobacteriaceae.Strains JSM111039and JSM111085could represent two novel species of the genusBacillus, and strains JSM111020, JSM111072and JSM111090could represent threenovel species within three characterized genera Pseudoalteromonas, Proteus andIdiomarina, respectively. The results presented above showed that there is abundantbacteria diversity in Crassostrea hongkongensis collected from the tidal flat of NaozhouIsland in the South China Sea. The antimicrobial activity of72strains were using the cylinder-plate method on8indicator microorganisms, i.e. three Gram-positive bacteria, three Gram-negativebacteria, and two fungi. Then research on phylogenetic analysis and biologicalcharacteristic of5strains with positive antimicrobial activity in16S rRNA genesequences. The results showed that the fermentation products of24strains in72isolation strains, had antimicrobial activity, and the positive rate was33.3%. The5strains were respectively belongs to Oceanimonas(JSM111024，JSM111027，JSM111029，JSM111083) and Nitratireductor（JSM111076）.Research on the systematics of some new taxa by polyphasic taxonomy, andanalysesed of the contrasting morphology, physiological and biochemical characters,cell chemical composition, phylogenetic analysis and DNA-DNA hybridization studies,to determined the taxonomic status of2strains. Bacillus nanhaiensis sp. nov.,Accession number: GU477780, with JSM111039T(DSM23009T=KCTC13712T) asthe type strain; Bacillus zhanjiangensis sp. nov., Accession number: HM460884, withJSM111085T(DSM23010T=KCTC13713T) as the type strain.These results suggest that abundant microbial diversity of oyster was present inisland of zhanjiang NaoZhou tidal zone. Among those strains, some new taxa andstrains with antimicrobial activity were the prospect exploit and utilization microbialresources.