The Dynamical Study Of Cyanophage PP And The Ecological Study Of Freshwater Virioplankton

In this study, we carried out an experiment to study the decay of cynaophage PP by solarUV-B and the photoreactivation repair by host cyanobacteria in one day at each seasonthroughout a year and the genetic variation of environmental cyanophage PP. By studying theone-step growth curve of cyanophage PP(host cells was from field samples), a mathematicmodel was established to explain the daily fluctuation of the titer of cyanophage PP. The resultsindicate that the cyanophage PP in the field could quickly cause the lysing of the host cell with arelatively high burst size. Although solar UV-B and other factors could cause the rapid decay ofcyanophage PP, host cell could rapidly repair the decayed cyanophage PP by photoreactivation(the repair limit was determined by the degree of the decay). The sequence alignment ofcyanophage pp from different sampling sites incidates that the genetic variation of cyanophagepp is relatively small in the environment. Thus the quantity relationship between cyanophage PPand its host is fundamental for maintaining the population and the ecological function ofcyanophage PP.We also studied the temporal and spatial distribution of virioplankton in East Lake, LiangziLake and other two water bodies that were suffered from Microcystis aeruginosa blooms inWuhan city, as well as the spatial distribution of virioplankton and lysogenic bacterium in severalwetlands in Hubei province. The results indicate that trophic level, especially organic material,and water temperature are key factors that influence the distribution of virioplankton, while thehost density (bacteriaplankton, in most cases) is the direct factor. In eutrophic water bodies, algalproductivity could influence virioplankton abundance by providing organic material. However,phycovirus and cyanophage are not the dominant components in virioplankton, nor could itcontrol the M. aeruginosa blooms. Lysogenicity could be the basic mechanism for themaintenance of virioplankton population in mesotrophic and hyper-eutrophic water bodies.