Life serves viruses

Sometimes I get the feeling that all life on Earth basically serves as a vehicle for viral replication and propagation. Viruses thrive in all three domains, they embed themselves in all creature’s genomes, they may lie dormant in the genome for eons or decimate whole populations in a few years, and they are the most abundant protein & DNA particle on earth. I am certain that their full impact on evolution is overwhelmingly larger than they are given credit for at present.

In a new article in PLoS Biology Clément Gilbert and Cédric Feschotte report their discover of  the DNA of hepadnaviridae viruses embedded in the genome of the zebra finch. By comparing the viral DNA to current viral DNA they dated it to to 19 million years ago. This places the  genomic infection in animals by hepadnaviridae which also include the hepatitis B virus  much earlier than thought. The hepadnaviridae also include the infamous hepatitis B virus, or HBV.

Credit: Daniel D. Baleckaitis, From: wikimedia commons

Hepadnaviruses infect a genome on a “one time only” basis, meaning that the same virus cannot jump around the genome and re-replicate like retroviruses (HIV for example) do. Therefore, the integration of each virus provided an event time stamp for the researchers to look at. They concluded that the insertion events into  the Finch’s genome and its ancestors’ genomes took place over several million years. And, of course, is still ongoing.

UPDATE: just after I hit “Publish”, two tweets came along from Ian Holmes and Peter Cock about another interesting paper on viruses in the service of evolution (or vice-versa). This one is from Lauren McDaniel and colleagues titles “High Frequency of Horizontal Gene Transfer in the Oceans“. Gene Transfer Agents or GTAs are virus-like particles that insert DNA into bacterial genomes. McDaniel and colleagues engineered GTAs to contain a marker gene  that provides antibiotic resistance. They placed the marked GTAs in bags filled with seawater, and floated the bags in the ocean overnight to simulate natural conditions. They found that  47% of the  bacteria in the bags incorporated the GTA-specific antibiotic resistance, therefore the GTA infected those bacteria. Paul Jones was quoted as saying “they’re promiscuous little bastards”, referring to  the large number of bacterial species GTAs infect. GTAs have little of their own genome, and they basically are vectors from transferring DNA between bacteria. So wow. Whole Lotta Shakin’ Goin’ On.

Finally, a CGI video of viruses at work. The Resident Evil bit spliced on at the end (2:10), while not scientifically accurate, is kinda cool by itself.

And of course…

Gilbert, C., & Feschotte, C. (2010). Genomic Fossils Calibrate the Long-Term Evolution of Hepadnaviruses PLoS Biology, 8 (9) DOI: 10.1371/journal.pbio.1000495

McDaniel, L., Young, E., Delaney, J., Ruhnau, F., Ritchie, K., & Paul, J. (2010). High Frequency of Horizontal Gene Transfer in the Oceans Science, 330 (6000), 50-50 DOI: 10.1126/science.1192243

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