也西湖噬藻体的分离与鉴定

【背景】噬藻体是一类特异性侵染蓝藻的病毒,广泛存在于淡水和海水水体中,参与调控宿主蓝藻的丰度和种群密度,被认为是潜在的蓝藻水华生物防控工具。但目前的研究多集中于海洋噬藻体,对淡水噬藻体的生物学特性和结构生物学等研究较少。【目的】分离更多种类的淡水噬藻体,为研究淡水噬藻体的三维结构、侵染机制、与宿主的共进化关系,及其在蓝藻水华防治中的应用提供理论基础。【方法】采集中国科学技术大学西校区内景观湖也西湖水华暴发水域的水样,利用液体培养基和双层固体平板法对17种宿主蓝藻进行筛选,通过NaCl-PEG沉淀法和氯化铯密度梯度离心分离和纯化噬藻体,并利用负染电镜观察噬藻体的形态,同时采用梯度稀释法测定裂解液的效价。【结果】发现也西湖的水样可特异性侵染本实验室分离自巢湖的一株拟鱼腥藻Pan。侵染后的裂解液中存在4株形态各异的噬藻体,包括1株短尾噬藻体和3株长尾噬藻体,其中包括首次发现的1株含有非典型长轴状头部结构的淡水噬藻体。【结论】也西湖作为巢湖流域的一个小型水体,具有与巢湖类似的水华蓝藻及其噬藻体分布谱,因此可以用于模拟大型湖泊进行相关分子生态学和生物防控的研究。

Isolation and characterization of cyanophages from the pond in the west campus of University of Science and Technology of China

Background] Cyanophages, the viruses that specifically infect cyanobacteria, are abundant in both marine and fresh waterbodies. They are involved in the regulation of the abundance and population density of cyanobacteria, thus considered as potential agents to prevent and control cyanobacterial bloom. However, previous studies mostly focus on marine cyanophages, rather than on those from freshwater. Objective] Isolation of as many as possible types of freshwater cyanophages for further studies of the 3-D structures, infection mechanism and co-evolution with the host cyanobacterium, in addition to potential application on prediction and control of cyanobacterial blooms. Methods] We collected water samples from the surface rich of cyanobacterial blooms in a small pond named Yexihu on the west campus of the University of Science and Technology of China, Hefei, China. In total 17 strains of cyanobacteria were applied to the screening against the collected water samples using liquid culture medium and double-layer plate. Cyanophages in the lysate were purified via NaCl-PEG precipitation followed by CsCl density gradient centrifugation, and further applied to morphology check using transmission electron microscopy. The titer of the lysate was determined by the serial dilution method. Results] The water samples could specifically infect a strain of Pseudanabaena termed Pan, which was isolated from the Lake Chaohu. The lysate contains four types of cyanophages with different morphology, one type of Podovirus and three types of Siphovirus. Notably, we found an atypical freshwater cyanophage with a prolate head for the first time. Conclusion] The water sample of Yexihu contains cyanophages that could specifically infect cyanobacteria of the Lake Chaohu, indicating that the pond Yexihu and the Lake Chaohu share a similar pattern of cyanobacteria and cyanophages. Thus, we can use Yexihu as a waterbody to mimic the related molecular ecology studies and cyanobacterial bloom control in the Lake Chaohu.