南海北部噬菌体与细菌群落的动态过程耦合研究

Bacteriophages (phages) are the major fraction of viruses, the most abundant biological entities in the ocean, with abundance more than bacteria by one order of magnitude. Phages play important roles in influencing the biogeochemical cycling of nutrients through infecting and lysing their bacterial hosts. The host-specific nature of viral infection makes phages powerful agents for controlling the diversity and community composition of their bacterial hosts. However, the ecological roles of bacteria for phages are often the ignored one between the two sides of the interaction between bacteria and phages. Here, we propose to investigate the co-variations between phages and bacteria in abundance and community structure at three marine time-series stations. Samples will be collected daily at Daya Bay, Sanya Bay and Yongxing Island during a time period of 60 days, and monthly or seasonally along a year. Moreover, seawater experimental incubations will be conducted and batch culturing samples will be collected. With such microbial and viral samples, we are trying to analyze the co-variations between viral abundance and bacterial abundance and production, between phage and total and active bacterial communities, between cyanophage and cyanobacterial communities, and between roseophage and roseobacterial communities. By doing so, this work will provide new information shedding light on answering the scientific questions as follows. First, are there significant correlations between the variations of phages and bacteria in abundance and community composition, and if yes, what are the significance levels of them? Second, do phage and bacterial communities respond to the environmental changes synchronously or with a time lag? Third, could the variations of bacterial abundance, diversity and community composition lead to significant constraint on those of phages? Ultimately, this work will focus to demonstrate the ecological roles of bacteria in phage community dynamics within their prey-predator relationship.

噬菌体是海洋病毒的主体，丰度约为细菌的10倍，通过裂解细菌影响海洋物质与能量循环。噬菌体因其宿主专一性被认为是调控细菌的多样性与群落结构的重要因素。然而，细菌对噬菌体的生态作用在噬菌体-细菌系统中多被忽视。本项目将在大亚湾、三亚湾、西沙永兴岛三处海洋生态站附近海域开展以日为单位、60日为周期与以月或季节为单位、1年为周期的时间序列连续观测、采样及现场培养实验。主要研究内容为：1）噬菌体丰度与细菌丰度及生产力的动态过程；2）总噬菌体与总细菌及活性细菌、蓝细菌噬菌体与蓝细菌、玫瑰杆菌噬菌体与玫瑰杆菌的群落动态耦合过程。项目拟解决的关键科学问题是：1）噬菌体与细菌的丰度和群落结构的动态过程的相关性如何？2）噬菌体与细菌的群落是否同步响应环境变化？3）细菌的丰度、多样性与群落结构的变异是否对噬菌体的丰度、多样性与群落结构有显著影响？项目的重点目标是阐明在噬菌体与细菌的生态关系中细菌对噬菌体的作用。

噬菌体是海洋病毒的主体，丰度约为细菌的10倍，通过裂解细菌影响海洋物质与能量循环。噬菌体因其宿主专一性被认为是调控细菌的多样性与群落结构的重要因素。不同尺度的时间序列研究能够精细刻画细菌与病毒的群落变异过程，以及二者的相互影响。本研究在三亚湾与大亚湾开展了不同尺度的时间序列研究，主要以海洋超微型蓝细菌与侵染它们的噬菌体为对象，分析它们的丰度与群落结构，以及影响它们的环境因素；同时，在环境中分离获得蓝细菌、玫瑰杆菌以及弧菌等细菌的噬菌体，分析它们的基因组多样性。通过基因组分析寻求保守的基因设计特定分子标记的引物，以供开展实时荧光定量PCR检测与高通量多样性分析。研究取得以下结果。1）在三亚湾与大亚湾开展了为期30日，每6-12小时观测采样1次的时间序列研究。发现总病毒的丰度在研究期内变化幅度较小，依次低于细菌、浮游真核生物与蓝细菌。蓝细菌丰度的变异性最大，然而蓝细菌病毒丰度的变异性在三亚湾小于蓝细菌，在大亚湾大于蓝细菌。潮汐引起的水团混合是影响细菌与病毒丰度的主要因素，细菌与病毒同步响应环境变化，二者之间未发现明显的控制与被控制过程。2）在三亚湾开展了季节性时间序列观测采样，同时以印度洋寡营养环境为对照，研究蓝细菌及其病毒的群落变异相关性。发现三亚湾蓝细菌及其病毒的丰度具有显著的季节性规律，在冬季显著小于其它季节；在群落结构上蓝细菌与其短尾噬菌体具有高度的相关性；蓝细菌肌尾病毒也具有明确的时空分布规律。3）在三亚湾开展蓝细菌噬菌体、玫瑰杆菌噬菌体与弧菌噬菌体的基因组多样性研究。蓝细菌短尾噬菌体具有保守的基因组结构与转录时序，而原绿球藻与聚球藻对短尾噬菌体侵染的转录响应是基本一致的。以玫瑰杆菌与弧菌为宿主，都分离获得了N4-like的短尾噬菌体，N4-like噬菌体具有保守的基因组结构，较短的潜伏期，N4-like噬菌体可能是近岸海域的重要病毒类群。4）针对蓝细菌与蓝细菌噬菌体，设计特定分子标记的引物，以开展实时荧光定量PCR检测与多样性分析。已完成针对蓝细菌的分子标记设计与验证，蓝细菌噬菌体的分子标记设计与验证工作在进行。综上，通过不同时空尺度的细菌与噬菌体的群落的耦合研究，结果显示细菌与噬菌体在时间尺度上未见明显的相互控制，而更倾向于共同响应环境的变动，在空间尺度上病毒具有与宿主相关的生物地理学分布格局。依托本项目已发表论文4篇，待发表论文4篇，培养研究生3名。