Research Highlight

Ocean Bacteria Infected by Strange Looking Viruses



Figure Legend: (A-B) Pelagiphage. (C) HTVC010P, the most abundant Pelagiphage.(D) Pelagiphage.( E) An infected SAR11 cell filled with Pelagiphage immediately before lysis (being split open).


NCMIR researchers aided in the discovery of the most abundant virus in the ocean. This virus, called a Pelagiphage, attacks the most abundant microorganism in our oceans, a type of marine bacteria called SAR11, with significant implications for how carbon moves between the atmosphere and our oceans. SAR11, a bacterium that's the most abundant organism in the oceans, survives where most other cells would die and plays a major role in the planet's carbon cycle. It had been theorized that SAR11 was so small and widespread that it must be invulnerable to attack. Pelagiphages are so strange-looking that scientists previously didn't even recognize what they were. Pelagiphage viruses are now known to infect SAR11 and routinely kill millions of these cells every second. And how this fight turns out is of more than casual interest, because SAR11 has a huge effect on the amount of carbon dioxide that enters the atmosphere, and the overall biology of the oceans. The findings disprove the theory that SAR11 cells are immune to viral predation. What the new research shows is that SAR11 is competitive, good at scavenging organic carbon, and effective at changing to avoid infection. Because of that, it thrives and persists in abundance even though the new viruses that have been discovered are constantly killing it. The viruses appear to be just as abundant as SAR11. SAR11 has several unique characteristics, including the smallest known genetic structure of any independent cell. Through sheer numbers, 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. SAR11 recycles organic matter, providing the nutrients needed by algae to produce about half of the oxygen that enters Earth's atmosphere every day. This carbon cycle ultimately affects all plant and animal life on Earth. Dr. Yanlin Zhao and Dr. Michael Schwalbach, from the laboratory of Dr. Stephen Giovannoni (Professor of Microbiology, Oregon State University), were responsible for isolating Pelagiphage. Dr. Ben Temperton then used their genome sequences to look for genetic traces of the phage in ocean samples collected from a variety of sites. Thomas Deerinck and Dr. Mark H. Ellisman from the National Center subsequently performed electron microscopy for Microscopy and Imaging Research, at UCSD. The team discovered that the Pelagiphage, HTVC010P is more numerous than any phage ever studied. These findings were reported Feb 13. in the journal Nature. .


Citation: Zhao, Yanlin*, Ben Temperton*, J. Cameron Thrash, Michael S. Schwalbach, Kevin L. Vergin, Zachary C. Landry, Mark Ellisman, Tom Deerinck, Matthew B. Sullivan and Stephen J. Giovannoni. (2013) Abundant SAR11 viruses in the ocean. Nature 494(7437): 357-360. doi: 10.1038/nature11921. (*Equal contribution) (PMID: 23407494; PMCID in progress)

Online version of the article in Nature