Population dynamics of Chesapeake bay virioplankton: Total-community analysis by pulsed-field gel electrophoresis

Recognition of viruses as the most abundant component of aquatic microbial communities has stimulated investigations of the impact of viruses on bacte rio- and phytoplankton host communities. From results of field studies to d ate, it is concluded that in most aquatic environments, a reduction in the number of bacteria on a daily basis is caused by viral infection. However, the modest amount of in situ virus-mediated mortality may be less significa nt than viral infection serving to maintain clonal diversity in the host co mmunities directly, through gene transmission (i,e,, transduction), and ind irectly, by elimination of numerically dominant host species. If the latter mechanism for controlling community diversity prevails, then the overall s tructure of aquatic viral communities would be expected to change as well o ver short seasonal and spatial scales, To determine whether this occurs, pu lsed-field gel electrophoresis (PFGE) was used to monitor the population dy namics of Chesapeake Bay virioplankton for an annual cycle (1 gear). Viriop lankton in water samples collected at six stations along a transect running the length of the bay were concentrated 100-fold by ultrafiltration, Virus es were further concentrated by ultracentrifugation, and the concentrated s amples were embedded in agarose. PFGE analysis of virus DNA in the agarose plugs yielded several distinct bands, ranging from 50 to 300 kb, Principal- component and cluster analyses of the virus PFGE fingerprints indicated tha t changes in virioplankton community structure were correlated with time, g eographical location, and extent of water column stratification, From the r esults of this study, it is concluded that, based on the dynamic nature of the Chesapeake Bay virioplankton community structure, the clonal diversity of bacterio- and phytoplankton host communities is an important component o f the virus community.