马里亚纳海沟可培养水生细菌的多样性

Diversity of culturable aquatic bacteria at different depths of the Mariana Trench

【目的】马里亚纳海沟是地球表面最深的海沟,环境极端多样,如高压、低温及无光,拥有独特的微生物资源。本研究旨在探究马里亚纳海沟不同深度水生细菌形态特征并挖掘可培养细菌资源。【方法】采集马里亚纳海沟7个层位海水(2-8727 m),利用原子力显微镜与扫描电镜观察水生微生物的形态特征;采用2种常规培养基(1/5×2216E和1/30×2216E)及6种选择性培养基(有机碳氮组合),结合切向流与高压富集培养进行水生细菌分离与鉴定。【结果】从不同深度水样中发现多种大小不一的细菌类群(130 nm-1.5μm),以球菌和杆菌为主。在表层水体中常见颗粒附着的细菌,在深层水体中常见自由游动的细菌。共鉴定365株可培养水生细菌,隶属于3个门、31个属与56个种。γ-变形菌纲(Gammaproteobacteria)是绝对优势类群(占据可培养细菌总数的62.7%),相对丰度在深层水体中高于浅层。交替单胞菌属(Alteromonas,21.8%)和亚硫酸杆菌属(Sulfitobacter,19.1%)是主要优势属,在浅层水体中占绝对优势。稀释的2216E与氨基酸培养基对海杆菌属的选择性更好,葡萄糖-甘露糖培养基与牛磺酸-乙醇酸培养基对稀有细菌的选择性更好。7株菌(5种)是潜在的新型细菌。此外,通过切向流富集培养与压力筛选培养分别分离得到70株(22属)可通过0.22-μm细菌(0.22-μm-passable bacteria)与33株(8属)耐压细菌。【结论】马里亚纳海沟不同深度水样中不同营养利用型细菌、可通过0.22-μm细菌与耐压细菌及其形态均具有丰富的多样性。本研究所获得的不同类型的细菌菌株为研究细菌在马里亚纳海沟中生物地球化学功能及其营养类型差异和高压适应机制奠定了菌株基础。

[Objective]The Mariana Trench is the deepest site on earth with diverse extreme conditions(e.g.,ultra-high hydrostatic pressure,low temperature and lack of light).It contains abundant microbial resources.The aim of this study is to explore aquatic microbial morphological characteristics and to mine culturable bacterial resources from different depths of the Mariana Trench.[Methods]Seawaters of seven depths(2-8727 m)from the Mariana Trench were collected.Aquatic microbial morphological characteristics were observed by atomic force microscopy and scanning electron microscopy.Combined with enrichment culture by using tangential flow system and high pressure device,two kinds of conventional media(1/5×2216 E and 1/30×2216 E)and six kinds of selective media(made up of combinations of organic carbon and nitrogen)were used for isolation and cultivation of aquatic bacteria.[Results]Various aquatic bacteria with different sizes(130 nm-1.5μm)were found at different depths,dominated by spherical or rod-shaped bacteria.Particle-associated bacteria were common in surface seawaters and free-living bacteria were common in deep seawaters.Belonging to 3 phyla,31 genera and 56 species,a total of 365 strains were identified.Gammaproteobacteria dominated(accounting for 62.7%of the total isolates)and its relative abundance in deep waters was higher than that in shallow waters.Alteromonas(21.8%)and Sulfitobacter(19.1%)were the most abundant genera,dominated in shallow water samples.The diluted 2216 E and amino acid medium were found to have a better selectivity to Sulfitobacter.The selectivity of glucose-mannose medium(GM)or taurine-glycolic acid medium(TG)to rare bacteria was better.Seven strains(five species)were potential novel bacteria.In addition,700.22-μm-passable strains(22 genera)and 33 piezotolerant strains(8 genera)were isolated,respectively.[Conclusion]There were rich diversities of different trophic,0.22-μm-passable and piezotolerant bacteria and their morphologies at different water depths of the Mariana Trench.This study provided unique resources of aquatic microorganisms to investigate their trophic types,high-pressure adaptation mechanisms and biogeochemical roles in the Mariana Trench.