Assessment of Ecological Roles of Cyanophages in Aquatic Environments using Molecular Approaches

在自然界中发现了高浓度的形态多样的海洋聚藻球菌（感染聚藻球菌属的病毒）。在水生环境中，如此丰富多样的噬藻体和蓝藻共存被认为是调节两者群落多样性的重要因素。最近的一些研究表明，在海洋生态系统中，噬藻菌可能占聚藻球菌死亡率的30%。然而，其他研究表明，无论是在近岸还是近海水域，噬藻体都不太可能是聚藻球菌死亡的主要原因。支持这两种不同观点的证据是基于从实验室细菌培养中收集的数据；在可能与自然界完全不同的条件下。到目前为止，还没有生物学方法来原位检测和量化有多少聚球菌细胞被噬菌体感染。为了评估噬菌体对自然微生物死亡率的影响，重要的是要确定被感染的自然种群的百分比。原位分子检测技术的发展可以为研究天然水生环境中噬菌体对聚球菌死亡率的生态影响提供新的思路。本研究由两部分组成。首先，从几种感染聚藻球菌代表菌株的海洋噬藻体中提取DNA聚合酶基因（DNA pol）序列，并将其用于研究海水中噬藻聚藻球菌的多样性和遗传关系。研究的第二部分将发展在海洋环境中被各种噬藻菌株感染的联球菌细胞百分比的原位分子检测。

High concentrations of morphologically diverse marine Synechococcus cyanophages (viruses which infect Synechococcus spp) are found in nature. Co existence of such abundant and diverse cyanophages and cyanobacteria in aquatic environments has been thought to be an important factor in regulating the community diversity of both groups. Some recent studies suggest cyanophages may account for 30% of Synechococcus mortality in marine ecosystems. However, other studies suggest it is unlikely for cyanophages to be major contributors to Synechococcus mortality in either inshore or offshore waters. The evidence supporting these two different opinions was based on data collected from bacterial cultures in the laboratory; at conditions which may be quite different from what occurs in nature. So far, there are no biological means to detect and quantify in situ how many Synechococcus cells are being infected by phages. To assess the effects of phages on natural microbial mortality, it is important to determine the percentage of the natural population that is being infected. Development of in situ molecular detection techniques can provide new insight into the ecological impact of phages on Synechococcus mortality in natural aquatic environments. This research is composed of two parts. First, DNA polymerase gene (DNA pol) sequences from several marine cyanophages which infect representatives of Synechococcus strains will be characterized and subsequently used for studying diversity and genetic relationships among Synechococcus cyanophages in seawater. The second part of the study will develop in situ molecular detection of the percentage of Syncechococcus cells infected by various strains of cyanophages in marine environments.