Summary: Ocean viruses alter ecosystems through host mortality, horizontal gene transfer and by facilitating remineralization of limiting nutrients. However, the study of wild viral populations is limited by inefficient and unreliable concentration techniques. Here, we develop a new technique to recover viruses from natural waters using iron‐based flocculation and large‐pore‐size filtration, followed by resuspension of virus‐containing precipitates in a pH 6 buffer. Recovered viruses are amenable to gene sequencing, and a variable proportion of phages, depending upon the phage, retain their infectivity when recovered. This Fe‐based virus flocculation, filtration and resuspension method (FFR) is efficient (> 90% recovery), reliable, inexpensive and adaptable to many aspects of marine viral ecology and genomics research.

Wild phage evolution: Bacteria possess a diversity of highly specific phage defense mechanisms that evolve rapidly and that account for a large proportion of bacterial genomes. These dynamics must be understood if phage therapy is to be seriously considered for clinical use. Hussain et al . studied a set of nearly clonal wild-caught Vibrio lentus hosts and their phage and found that the hosts segregated into two groups infected by different viruses (see the Perspective by Meaden and Fineran). Puzzlingly, both host groups have the same surface phage receptors. This apparent paradox was resolved by sequencing of the hosts, which revealed distinct suites of endogenous but mobile phage defense elements (PDEs) in the two host phenotypes. Indeed, the PDEs constitute a large fraction of the flexible noncore genome of the bacteria. This means the PDEs can evolve and transfer from cell to cell without interfering with metabolic processes required to synthesize essential cell surface molecules. —CA