马里亚纳海沟共培养细菌多样性动态变化及潜在微生物互作关系

马里亚纳海沟是世界已知最深的海沟，其寡营养、高压、低温、低氧等极端的深海环境孕育出独特的细菌群落结构及多样性特征。选取寡营养培养基对马里亚纳海沟海水及表层沉积物分别进行液体共培养，并在不同培养阶段取样进行高通量测序，分析细菌群落结构组成及其多样性的动态变化，探讨微生物之间可能的互作关系。研究结果表明：液体共培养样品中一共检测到19个门、34个纲、76个目、131个科、227个属的细菌，其中变形菌门（Proteobacteria）和拟杆菌门（Bacteroidetes）为优势菌群，其次为厚壁菌门（Firmicutes）；与其他样品相比，1000米海水样品中细菌群落的多样性最高，并且蓝细菌门（Cyanobacteria）具有更高的相对丰度。共培养样品中细菌丰富度、多样性、群落结构均随培养时间而改变，其中共培养中期样品的细菌多样性较高；表层沉积物样本中，盐单胞菌属（Halomonas）可能由于较强的竞争能力在共培养后期占据优势地位。基因功能预测与代谢通路富集结果显示，随着共培养时间的增加，微生物生长相关的代谢通路丰度明显下降，而与互作相关的代谢通路丰度明显增加。共培养样品检测到的细菌多样性远高于单独分离培养的多样性，仅有少量菌属为单独分离培养与共培养样品均检测到的共有属。综上所述，马里亚纳海沟细菌群落中存在竞争、互利共生的相互作用，共培养法有利于揭示细菌间的互作关系。研究为深渊及深海等极端环境下微生物生态系统组成及维持奠定了理论基础，也为进一步研究极端微生物的生存策略提供了科学指导。

Dynamic changes of bacterial diversity and microbial interactions in co-culture samples from the Mariana Trench

As the deepest oceanic trench currently known on earth, the Mariana Trench breeds unique bacterial community structure and diversity characteristics due to its deep-sea extreme environment such as oligotrophy, high pressure, low temperature, and low oxygen. In this study, oligotrophic media were selected for liquid co-culture of seawater and surface sediment samples from the Mariana Trench, and the samples were taken at different culture times for high-throughput sequencing, in which way we analyzed the dynamics of bacterial community structure composition and diversity as well as explored the possible interactions among microorganisms. The results showed that a total of 19 phyla, 34 classes, 76 orders, 131 families, 227 genera of bacteria were detected in the liquid co-culture samples, among which Proteobacteria and Bacteroidetes were the dominant taxa, followed by Firmicutes. Compared to the others, the seawater sample collected from 1000 m below sea level had the highest bacterial community diversity and the higher relative abundance of Cyanobacteria. The bacterial richness, diversity, and community structure in the co-culture samples all changed with culturing time, and there was especially higher bacterial community diversity in the middle stage of co-culture samples. In the surface sediment samples, Halomonas occupied a dominant position in the late stage of co-culture probably due to its strong competitiveness. Gene function prediction and metabolic pathway enrichment showed that with the increasing time of co-culture, the abundance of metabolic pathways associated with microbial growth decreased significantly, while the abundance of metabolic pathways related to microbial interactions increased significantly. The diversity of bacterial community detected in co-culture samples was much higher than that of the isolated culture samples, and only a small number of bacteria genera were identified by both culturable methods and liquid co-culture in common. In conclusion, there are microbial interactions such as competition and mutualistic symbiosis in the bacterial community of the Mariana Trench, and the liquid co-culture method is beneficial to reveal the bacterial interactions. This study provides a theoretical basis for the composition and maintenance of microbial ecosystems in extreme environments like hadal environments and deep-sea, and also provides scientific guidance for the further study on the survival strategies of extremophile.