Insight into the unknown marine virus majority

Abstract

Viruses of marine bacteria (bacteriophage) have been characterized since the mid-20th century (1). However, it took several additional decades before electron micrographs of seawater revealed that particles of virus-like morphology could exceed concentrations of 1 million per milliliter of seawater (2, 3), and that phage infection could cause substantial mortality in marine bacterial communities (4). Subsequent research in the field of marine viral ecology has focused on the characterization of the diversity of the virioplankton (community of extracellular viruses), elucidating how viruses influence the community dynamics and evolution of their hosts and ultimately the role viruses play in biogeochemical cycling. Critical to the understanding of viral ecology is the identification of the constituents of the viral community and whom they infect. This is a formidable challenge because there are thousands of different types of viruses in every liter of seawater (5) that are mostly distantly related to the catalog of known viruses, and whose morphology and genotype do not identify the host that they infect. A clear, albeit challenging, path forward to gaining a greater understanding of viral ecology is the isolation and characterization of viruses that infect hosts who play important roles in the environment. In PNAS, Kang et al. (6) make a significant contribution to the field with a report describing the isolation and characterization of a bacteriophage, HMO-2011, which infects a member of the SAR116 clade, a group of marine bacteria that are abundant and … [↵][1]2E-mail: aculley{at}hawaii.edu. [1]: #xref-corresp-1-1