Kinetics of adsorption of two distinct viruses to marine planktonic diatom <i>Chaetoceros tenuissimus</i> Meunier

Adsorption onto the host cell is an important step in viral infection. In this study we aimed to clarify host-strain-specific adsorption of diatom viruses. The adsorption kinetics of Chaetoceros tenuissimus DNA virus (CtenDNAV-II) and Chaetoceros tenuissimus RNA virus (CtenRNAV-II) were compared using the marine planktonic diatoms Chaetoceros socialis f. radians strain NIES-3713 and Chaetoceros tenuissimus strains NIES-3714 and NIES-3715, which possess different viral susceptibility spectra. CtenDNAV-II and CtenRNAV-II viruses showed significant adsorption towards C. tenuissimus strains NIES-3714 and NIES-3715, respectively, which were the original host strains used for their isolation, and the estimated adsorption coefficients were 1.4±0.9×10−9 mL min−1 and 2.7±1.1×10−9 mL min−1, respectively. In this study, adsorption was not detected for incompatible host–virus combinations (that is, absence of host cell lysis after viral inoculation). However, virus adsorption was not detected even for compatible combinations of C. tenuissimus NIES-3715 and CtenDNAV-II and C. socialis NIES-3713 and CtenRNAV-II, which may be attributed to the limit of detection in the present experiment. Nevertheless, the results suggest that host–virus affinities differ widely even among compatible host–virus combinations, resulting in changes in clonal composition and population dynamics in natural environments. Thus, this study provides important information for understanding the ecological relationships between diatoms and viruses.