| The number and diversity of viral sequences that are identified in metagenomic data far exceeds that of experimentally characterized virus isolates. In a recent workshop, a panel of experts discussed the proposal that, with appropriate quality control, viruses that are known only from metagenomic data can, and should be, incorporated into the official classification scheme of the International Committee on Taxonomy of Viruses (ICTV). Although a taxonomy that is based on metagenomic sequence data alone represents a substantial departure from the traditional reliance on phenotypic properties, the development of a robust framework for sequence-based virus taxonomy is indispensable for the comprehensive characterization of the global virome. In this Consensus Statement article, we consider the rationale for why metagenomic sequence data should, and how it can, be incorporated into the ICTV taxonomy, and present proposals that have been endorsed by the Executive Committee of the ICTV. NATURE REVIEWS | MICROBIOLOGY VOLUME 15 | MARCH 2017 | 161 CONSENSUS STATEMENT © 2 0 1 7 M a c m i l l a n P u b l i s h e r s L i m i t e d , p a r t o f S p r i n g e r N a t u r e . A l l r i g h t s r e s e r v e d .

This paper presents standards and best practices for reporting genome sequences of uncultivated viruses.Supplementary informationThe online version of this article (doi:10.1038/nbt.4306) contains supplementary material, which is available to authorized users.

Loss rates and loss processes for viruses in coastal seawater from the Gulf of Mexico were estimated with three different marine bacteriophages. Decay rates in the absence of sunlight ranged from 0.009 to 0.028 h-1, with different viruses decaying at different rates. In part, decay was attributed to adsorption by heat-labile particles, since viruses did not decay or decayed very slowly in seawater filtered through a 0.2-jLm-pore-size filter (0.2-jum-filtered seawater) and in autoclaved or ultracentrifuged seawater but continued to decay in cyanide-treated seawater. Cyanide did cause decay rates to decrease, however, indicating that biological processes were also involved. The observations that decay rates were often greatly reduced in 0.8or 1.0-jLm-filtered seawater, whereas bacterial numbers were not, suggested that most bacteria were not responsible for the decay. Decay rates were also reduced in 3-jim-filtered or cycloheximide-treated seawater but not in 8-jim-filtered seawater, implying that flagellates consumed viruses. Viruses added to flagellate cultures decayed at 0.15 h-1, corresponding to 3.3 viruses ingested flagellate-' h-1. Infectivity was very sensitive to solar radiation and, in full sunlight, decay rates were 0.4 to 0.8 h-1. Even when UV-B radiation was blocked, rates were as high as 0.17 h-1. Calculations suggest that in clear oceanic waters exposed to full sunlight, most of the virus decay, averaged over a depth of 200 m, would be attributable to solar radiation. When decay rates were averaged over 24 h for a 10-m coastal water column, loss rates of infectivity attributable to sunlight were similar to those resulting from all other processes combined. Consequently, there should be a strong diel signal in the concentration of infectious viruses. In addition, since sunlight destroys infectivity more quickly than virus particles, a large proportion of the viruses in seawater is probably not infective. * Corresponding author. t Contribution no. 841 of the Marine Science Institute.