Extra peptidase of a cyanophage confers its stronger lytic effect on bloom-forming Microcystis aeruginosa

Microcystis covers important cyanobacteria species that causes harmful algal blooms. Cyanophages are viruses that infect and lyse cyanobacteria and have been considered as potential cyanobacteria control strategy. Present study isolated two cyanophage strains, MaMV-CH01 (CH01) and MaMV-CH02 (CH02), infecting M. aeruginosa. Growth curves showed that CH01 has a stronger proliferation ability and host cell lysis capability than CH02. Combined with genomic, gene structure and function analysis, as well as biologic testing including infectivity, we confirmed that there is widespread horizontal gene transfer between the cyanophages and cyanobacteria, enabling the cyanophages to carry a series of auxiliary metabolic genes (AMG) related to host's metabolism. Moreover, compared with CH02, the cyanophage CH01 carrying extra AMG, a peptidase encoding gene (82R), exhibited stronger lytic activity against its host. Expression of CH01 82R in vitro showed strong bacteriostatic activity. Further, testing the cyanophage's ability to form plaques showed that the CH01(AMG⁺), which encodes the aforementioned peptidase, can form larger plaques, with an area of about threefold than that formed by CH02(AMG⁻). Above results indicated that the cyanophages with specific peptidase possessed stronger algicidal efficiency, which provided a direction for finding efficient cyanophages to regulate the population of bloom-forming cyanobacteria.