While the microbes in a single drop of water could outnumber a small city's population, the number of viruses in the same drop-;the vast majority not harmful to humans could be even larger.
Viruses infect bacteria, archaea and eukaryotes, and they range in particle and genome size from small, to large and even giant.
The genomes of giant viruses are on the order of 100 times the size of what has typically been associated with viruses, while the genomes of large viruses may be only 10 times larger. And yet, while they are found everywhere, comparatively little is known about viruses, much less those considered large and giant.
In a recent study published in the journal Nature , a team led by researchers at the U.S. Department of Energy (DOE) Joint Genome Institute (JGI), a DOE Office of Science User Facility located at Lawrence Berkeley National Laboratory (Berkeley Lab) uncovered a broad diversity of large and giant viruses that belong to the nucleocytoplasmic large DNA viruses (NCLDV) supergroup.
The expansion of the diversity for large and giant viruses offered the researchers insights into how they might interact with their hosts, and how those interactions may in turn impact the host communities and their roles in carbon and other nutrient cycles.
This is the first study to take a more global look at giant viruses by capturing genomes of uncultivated giant viruses from environmental sequences across the globe, then using these sequences to make inferences about the biogeographic distribution of these viruses in the various ecosystems, their diversity, their predicted metabolic features and putative hosts." Tanja Woyke, study senior author
Woyke heads JGI's Microbial Program.
The team mined more than 8,500 publicly available metagenome datasets generated from sampling sites around the world, including data from several DOE-mission relevant proposals through JGI's Community Science Program.
Proposals from researchers at Concordia University (Canada), University of Michigan, University of Wisconsin-Madison, and the Georgia Institute of Technology focused on microbial communities from freshwater ecosystems, including, respectively, the northern Lakes of Canada, the Laurentian Great Lakes, Lake Mendota and Lake Lanier were of particular interest. Sifting out and reconstructing virus genomes
Much of what is known about the NCLDV group has come from viruses that have been co-cultivated with amoeba or with their hosts, though metagenomics is now making it possible to seek out and characterize uncultivated viruses. For instance, a 2018 study from a JGI-led team uncovered giant viruses in the soil for the first time.
The current study applied a multi-step approach to mine, bin and then filter the data for the major capsid protein (MCP) to identify NCLDV viruses. JGI researchers previously applied this approach to uncover a novel group of giant viruses dubbed "Klosneuviruses." Related Stories
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