(ORDO NEWS) — An “amazing” and “unexpected” variety of giant virus-like particles have been found in the soil of Harvard Forest, Massachusetts. These particles are not only anomalously large, but also have “previously unimaginable” structures that challenge our understanding of giant viruses and viral diversity.
The researchers who made this discovery believe that the cornucopia of viral morphotypes found in the Harvard Forest calls into question our current understanding of the virosphere and its structural heterogeneity. The results obtained allow us to look into the complex world of soil viruses and suggest that the high genetic diversity of giant viruses corresponds to a diverse and previously unknown particle structure.
Virus particles have strange appendages and internal structures, some of which have never been seen before. These include tubular protrusions, fibers, internal channels, double capsids, and tails, which give them the bizarre names “turtle”, “haircut” and “Christmas star”.
Using transmission electron microscopy, the team found that soil samples were infested with “an unexpected variety of soil [virus-like particles] in a size fraction of 0.2 µm to 1.2 µm.” This is important because the largest virus ever discovered, found in 2014 in the permafrost of Siberia, was 1.5 µm wide, comparable to the size of a small bacterium.
The researchers found that several hundred grams of forest soil contained a greater variety of capsid morphotypes than all giant viruses isolated so far combined. They think this observation is even more striking when you consider that they only imaged an infinitesimal fraction of the viral diversity present in these soil samples.
The results highlight how much we still have to learn about the strange and wonderful world of giant viruses. The researchers hope that now other scientists will want to study this unusual variety and find out whether it is characteristic only of soil ecosystems or the aquatic environment is also home to a huge number of giant viral particles.
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