硇洲岛潮汐带牡蛎相关可培养细菌多样性

Biodiversity of culturable bacteria associated with Crassostrea hongkongensis from the tidal flat of Naozhou Island in the South China Sea

摘要:

【目的】了解南海硇洲岛潮汐带香港巨牡蛎(Crassostrea hongkongensis)相关可培养细菌的多样性。【方法】应用纯培养法分离样品中的细菌(含放线菌), 采用基于16S rRNA基因序列的系统发育分析方法研究这些分离菌株的生物多样性。【结果】用补充0–25% (w/v) NaCl的MA、MH和NA培养基从样品中分离到102株细菌, 在形态观察和部分生理生化实验结果的基础上去冗余, 选取74个代表性菌株进行基于16S rRNA基因序列的系统发育分析。结果表明, 这些菌株归为38个物种, 属于4个大的系统发育类群(Gamma-proteobacteria, alpha-Proteobacteria, Bacteroidetes, Firmicutes)的16个科、18个属。大多数菌株属于Gamma-Proteobacteria亚门(45株, 60.8%), 其余依次是Firmicutes门(12株, 16.2%)、Bacteroidetes门(11株, 14.9%)和Alpha-Proteobacteria亚门(6株, 8.1%)。大多数菌株与其系统发育关系最密切的有效发表种典型菌株之间(16S rRNA基因序列相似性为94.3%–99.8%)存在一定的遗传差异, 其中JSM 111069可能代表Carnobacteriaceae科的潜在新属; 菌株JSM 111039和JSM 111085可能分别代表Bacillus属的两个新物种, 菌株JSM 111020、JSM 111072和JSM 111090可能分别代表Pseudoalteromonas、Proteus和Idiomarina属的新物种。【结论】南海硇洲岛潮汐带牡蛎中存在较为丰富的原核生物多样性, 并潜藏着一定数量的微生物新类群(物种)。

Abstract:

[Objective] To investigate the diversity of cultivable bacteria isolated from Crassostrea hongkongensis collected from the tidal flat of Naozhou Island (20°52′–20°56′ N, 110°33′–110°38′ E) in the South China Sea. [Methods] Bacteria strains were isolated from homogenates of the sample by using conventional culture-dependent method, and then the isolated strains were investigated by using a phylogenetic analysis based on the 16S rRNA gene sequences. [Results] We isolated 102 bacteria strains from the sample on a number of media [MA (marine agar 2216), MH (moderate halophilic medium agar), NA (nutrient agar)] supplemented with 0–25% (W/V) NaCl. On the basis of the results of some morphological, physiological and biochemical tests, we selected 74 strains to perform a further phylogenetic analysis. Our results showed that the 74 isolates represented 38 species, belonging to 18 genera (Idiomarina, Morganella, Proteus, Halomonas, Paracoccus, Wohlfahrtiimonas, Marinobacter, Vibrio, Pseudoalteromonas, Shewanella, Oceanimonas, Nitratireductor, Myroides, Bacillus, Virgibacillus, Staphylococcus, Enterococcus, Trichococcus) of 16 families (Idiomarinaceae, Enterobacteriaceae, Halomonadaceae, Rhodobacteraceae, Xanthomonadaceae, Alteromonada- ceae, Vibrionaceae, Pseudoalteromonadaceae, Shewanellaceae, Aeromonadaceae, Phyllobacteriaceae, Flavobacteriaceae, Bacillaceae, Staphylococcaceae, Enterococcaceae, Carnobacteriaceae) in 4 phylogenetic groups (Gamma-Proteobacteria, Alpha-Proteobacteria, Bacteroidetes, Firmicutes). The most of isolates were within the subphylum Gamma-Proteobacteria (45 strains, 60.8%), followed by Firmicutes (12 strains, 16.2%), Bacteriodetes (11 strains, 14.9%) and Alpha-Proteobacteria (6 strains, 8.1%). The phylogenetic analysis results suggested that there were obvious genetic divergences between most isolates and their closest type strains (16S rRNA gene sequence similarities ranged from 94.3% to 99.8%). The results also showed that, out of the 74 isolates, at least 6 strains could represent potential new taxa. Strain JSM 111069 could represent a novel genus in the family Carnobacteriaceae. Strains JSM 111039 and JSM 111085 could represent two novel species of the genus Bacillus, and strains JSM 111020, JSM 111072 and JSM 111090 could represent three novel species within three characterized genera Pseudoalteromonas, Proteus and Idiomarina, respectively. [Conclusion] The results presented above showed that there are abundant bacteria diversity in Crassostrea hongkongensis collected from the tidal flat of Naozhou Island in the South China Sea.