期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2014
卷号：111
期号：44
页码：15786-15791
DOI：10.1073/pnas.1401322111
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceWithin aquatic ecosystems viruses facilitate horizontal gene transfer, biogeochemical cycling, and energy transfer by infecting and lysing microbial host cells. Despite their critical role in ecosystem function we understand little of the biological, ecological, and evolutionary features of most viruses in nature. We identify ribonucleotide reductase (RNR) genes as superior markers of viral diversity. RNR genes are distributed over a broad range of viruses. The most abundant RNR genes in marine environments are from novel groups only distantly related to known viruses. Frequency distributions of RNR clades within viral metagenome sequence libraries support predictions made by the "kill the winner" hypothesis, indicating that specialist podoviruses specifically adapted to infecting abundant heterotrophic bacterioplankton predominate within the virioplankton. Virioplankton play a crucial role in aquatic ecosystems as top-down regulators of bacterial populations and agents of horizontal gene transfer and nutrient cycling. However, the biology and ecology of virioplankton populations in the environment remain poorly understood. Ribonucleotide reductases (RNRs) are ancient enzymes that reduce ribonucleotides to deoxyribonucleotides and thus prime DNA synthesis. Composed of three classes according to O2 reactivity, RNRs can be predictive of the physiological conditions surrounding DNA synthesis. RNRs are universal among cellular life, common within viral genomes and virioplankton shotgun metagenomes (viromes), and estimated to occur within >90% of the dsDNA virioplankton sampled in this study. RNRs occur across diverse viral groups, including all three morphological families of tailed phages, making these genes attractive for studies of viral diversity. Differing patterns in virioplankton diversity were clear from RNRs sampled across a broad oceanic transect. The most abundant RNRs belonged to novel lineages of podoviruses infecting -proteobacteria, a bacterial class critical to oceanic carbon cycling. RNR class was predictive of phage morphology among cyanophages and RNR distribution frequencies among cyanophages were largely consistent with the predictions of the "kill the winner-cost of resistance" model. RNRs were also identified for the first time to our knowledge within ssDNA viromes. These data indicate that RNR polymorphism provides a means of connecting the biological and ecological features of virioplankton populations.
