Oceans Have Been The Stage For Earth's Longest Ongoing Battle Between Bacteria And A Virus
February 14, 2013

Oceans Have Been The Stage For Earth’s Longest Ongoing Battle Between Bacteria And A Virus

April Flowers for redOrbit.com - Your Universe Online

A new study led by Oregon State University reveals that the greatest battle in Earth's history has been going on for hundreds of millions of years. And the battle, which no one knew existed until now, is far from over.

The findings of this study were published in a recent issue of Nature.

On one side of the battle lines stands SAR11, a bacterium that´s the most abundant organism in the oceans, surviving where most other cells would die and playing a major role in the planet´s carbon cycle. Scientists have theorized that SAR11 was so small and widespread it must be invulnerable to attack.

On the other side of the battle are "Pelagiphages," viruses so strange looking that scientists previously did not recognize what they were. These viruses are now known to infect SAR11, routinely killing off millions of these cells every second. SAR11 has a huge effect on the amount of carbon dioxide (CO2) that enters the atmosphere, and the overall biology of the oceans, making this microscopic battle of utmost importance.

“There´s a war going on in our oceans, a huge war, and we never even saw it,” said Stephen Giovannoni, a professor of microbiology at Oregon State University. “This is an important piece of the puzzle in how carbon is stored or released in the sea.”

The research team, consisting of members from OSU´s High Throughput Culturing Laboratory; the University of Arizona´s Tucson Marine Phage Lab; University of California/San Diego´s (UCSD) National Center for Microscopy and Imaging Research; and the Monterey Bay Aquarium Research Institute (MBARI), outlined the discovery of this ongoing conflict and the implications of the battle for the biology and function of ocean processes. The theory that SAR11 cells are immune to viral predation has been debunked by this study.

“In general, every living cell is vulnerable to viral infection,” said Giovannoni, who first discovered SAR11 in 1990. “What has been so puzzling about SAR11 was its sheer abundance; there was simply so much of it that some scientists believed it must not get attacked by viruses.”

The new research reveals that SAR11 is competitive, good at scavenging organic carbon, and effective at changing to avoid infection. This is how it thrives and persists despite being under constant attack by new viruses.

OSU postdoctoral researchers Yanlin Zhao, Michael Schwalbach and Ben Temperton discovered the Pelagiphage viral families using traditional methods of growing cells and viruses from nature in a laboratory instead of sequencing DNA from nature. The computers could not recognize the DNA because the viruses are so unique.

"The viruses themselves, of course, appear to be just as abundant as SAR11,” Giovannoni said. “Our colleagues at the University of Arizona demonstrated this with new technologies they developed for measuring viral diversity.”

Among the unique characteristics of SAR11 is having the smallest known genetic structure of any independent cell. This microbe has a huge role in consuming organic carbon, which it uses to generate energy while producing carbon dioxide and water in the process, just by sheer numbers. SAR11 is a scavenger, recycling organic matter, providing the nutrients needed by algae to produce about half of the oxygen that enters Earth´s atmosphere every day.