The Inactive Effect Of Ultraviolet On Cyanophage PP And Its Photoreactivation By Host Cyanobacteria

Cyanophages, Which distributed widely in aquatic system,can specifically infect cyanobacteria,so they have an importent role in ecology.The infectivity of Cyanophages can be influenced by many environmental factors.The ultraivolet radiation is considered as the main factor affecting the inactivity of cyanophage.So experiment was carried to study the inactivity of cyanophage by ultraivolet radiation and its photoreactivation by host cyanobacteria. Results are as followed:After cyanophage was exposed to sunlight for 3 hours,the inactive rate may reach 90.3% in summer, while the number is only 42.4% in winter; after 6 hours'radiation, the inactive rate can reach 99.2% in summer and 87.1% in winter respectively; for a whole day's radiation, the inactive rate can be as high as 99.3% in summer and 94.1% in winter.It demonstrates that cyanophage can be inactived by sunlight obviously. With the prolong of the exposing time in sunlinght,the photoreactive rate decreased: for samples UV-damaged in summer,the repair rates are 49%, 12% and 1.3% for samples exposed to sunlight for 3 hours, 6 hours,and 9 hours respectively; for samples UV-damaged in winter, the repair rates are 57%,31% and 15% for samples exposed to sunlight for 3 hours, 6 hours,and 7.5 hours respectively . It is quite clear that the repair rate is much lower in summer than in winter. The seasonal research carried out in field conditions(East Lake) demonstrates: the inactive rate decreases with the increase of depth,and reaches its highest point as 92.1% in surface water(depth is 20cm) ; the inactive rate in surface water is higher in spring and summer (92.1-83.3% ) than that in automn and winter(67-30%); the photoreaction rate increases with the decrease of the inactivie rate as well as with the increase of the repair time , but the hightest repair rate can not exceed the limit of 65%.Experiment carried out inside the lab suggest that: [N] concentration has no effect on host cyanobacteria's repair rate; while host's repair capability varies with...