Viruses are now known to be the most numerically dominant form of life in the world's oceans. This revelation has raised a myriad of questions concerning the ecological role of viruses in the oceans. This study will investigate the genetic significance of viruses in the marine environment. Viruses could be a significant component of the oceanic dissolved (<0.2 um) nucleic acid pools and they also have the potential to alter bacterial gene pools by effecting gene transfer by transduction and viral mediated transformation. To investigate the gentic significance of viruses in the marine environment this study wil pursue the following three research objectives: 1) To determine viral abundance in estuarine, coastal, and offshore environments in surface and subsurface waters, and to develop methods for direct viral enumeration in sediments. The relationship between viral abundance and total (autotrophic and heterotrophic) host pool size will be assessed, as well as the relationship with particulate and dissolved DNA content. 2) To determine the proportion of particulate and dissolved nucleic acids that are contained in virus particles in estuarine, coastal, and offshore waters. Methods will be developed to quantitate viral DNA directly and relate it to bacterial and "free" (i.e. soluble as opposed to that encapsulated in virons) in oceanic samples. 3) To determine the potential for gene transfer by transduction in the marine environment by investigating the presence of temperate phage and lysogenic host bacteria. Using both isolated phage-host systems and natural viral and bacterial assemblages, the study will determine the presence of temperate phage/lysogenic hosts by chemical and physical induction of lysis. Once lysogens have been identified, these will be used in studies on the transfer of chromosomal DNA and broad host range plasmids by transduction. This research will begin to answer the questions of the role of viruses in the oceanic gene pool.
