Infectivity of algal viruses studied by chlorophyll fluorescence

Algal virus infection proceeds via the specific recognition of the host cell wall, penetration of the cell wall and transfer of genetic material into the cytoplasm of the host cell. This process is similar to that which occurs when bacteriophage infect bacteria so that techniques and concepts developed to study bacteriophage are applicable to algal virus studies. By measuring virus-induced changes in chlorophyll fluorescence we have redefined classical studies on the distribution of infectivity. We show that infectivity does not follow a Poisson distribution with a fixed mean, n. By analysing the infectivity of algal viruses over a broad range of virus:cell ratios we have obtained a corrected Poisson distribution that reflects the probability of multiple virus particles attached per cell and is equally applicable to algal viruses and bacteriophage.