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

Abstract:

[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.