Abstract
Microcystis aeruginosa, as one of the major players in algal bloom, produces microcystins, which are strongly hepatotoxic, endangering human health and damaging the ecological environment. Biological control of the overgrowth of Microcystis with cyanophage has been proposed to be a promising solution for algal bloom. In this study, a novel strain of Microcystis cyanophage, MinS1, was isolated. MinS1 contains an icosahedral head approximately 54 nm in diameter and a 260 nm-long non-contractile tail. The phage genome consists of a linear, double-stranded 49,966 bp DNA molecule, which shares very low homology with known phages in the NCBI database (only 1% of the genome showed weak homology with known phages when analyzed by megablast). The phage contains 75 ORFs, of which 23 ORFs were predicted to code for proteins of known function, 39 ORFs were predicted to code for proteins of unknown function, and 13 ORFs showed no similarity to any protein sequences. Transmission electron microscopy and phylogenetic analysis showed that MinS1 belongs to the family Siphoviridae. Various experiments confirmed that the phage could infect several different orders of cyanobacteria, including Chroococcales, Nostocales, Oscillatoriales, Hormogonales, and Synechococcales, indicating that it has a very broad host range. In addition, MinS1 has no known antibiotic tolerance genes, virulence genes, and tRNAs, and it is tolerant to temperature, pH, UV, and salinity, suggesting that MinS1 has good potential for application as a biological control agent against cyanobacterial blooms. This study expands the diversity and knowledge of cyanophages, and it provides useful information for the development of novel prevention and control measures against cyanobacterial blooms.
Highlights
Water eutrophication is a global water pollution problem, which causes massive production of cyanobacteria [1,2]
The 30 mL samples of surface cyanobacterial bloom water used for cyanophage separation were collected from the Mayang Stream (24◦ 320 37.81” N 117◦ 460 26.40” E), in Fujian, China, and centrifuged at 12,000 g for 20 min at 4 ◦ C
The plaques resulting from MinS1 lysis appeared clear and circular, with diameters of 3–4 mm, following a 4-day incubation (25 ◦ C, 2000 Lux, 12 h:12 h light–dark cycle) on host algal plates at a multiplicity of infection (MOI) of 0.1 (Figure 1a)
Summary
Water eutrophication is a global water pollution problem, which causes massive production of cyanobacteria [1,2]. The latter challenge can lead to cyanobacteria blooms [3], which have become a common occurrence in water bodies worldwide. Viruses infecting cyanobacteria are referred to as cyanophages, and they can play major roles in the dynamics, genetic diversity, and structure of cyanobacterial communities [9,10]. These cyanophages inhibit the production and release of algal toxins and are considered to have significant potential as biological control agents for harmful cyanobacterial blooms Algal toxins, are hepatotoxic, neurotoxic, reproductive toxic, genotoxic, and tumor promoting, causing great economic losses to aquaculture and posing risks to the safety of aquatic products for consumption [7,8].
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