OREGON STATE UNIVERSITY

Oregon scientists break through with important bacteria

08/07/2002

CORVALLIS - Microbiologists at Oregon State University have used sensitive new procedures to grow one of the Earth's tiniest, most abundant and least understood life forms in their laboratory, paving the way for a deeper understanding of the creature's g lobal ecological role, the international scientific journal Nature reported today.

The breakthrough, in Oregon State's Laboratory for the Isolation of Novel Species, involves "SAR11." These bacteria are widespread in the world's oceans and have been detected in freshwater lakes, according to microbiologist Stephen Giovannoni, the lab's director and one of the authors of the article in the Aug. 8 issue of Nature.

Ongoing research in OSU's Laboratory for the Isolation of Novel Species is focused on how abundant SAR11 bacteria are and on understanding the biochemical mechanisms that allow them to function in the Earth's largest ecosystem, the oceans.

In addition, the Oregon State researchers are working with scientists at Diversa Corporation, a biotechnology firm based in San Diego, to sequence the genome, or entire genetic makeup, of SAR11.

Giovannoni said SAR11 and similar little-understood microorganisms that are obviously important in global food chains "also are staggeringly important to the oceanic carbon cycle," linked to phenomena such as natural and human-induced global warming.

 

SAR11 initially was identified in 1990 in water samples the OSU research team took from the Sargasso Sea, an area in the Atlantic Ocean's so-called Bermuda Triangle off the East Coast of the United States. There are about a million bacteria in every teaspoon of seawater, and evidence suggests that SAR11 is one of the most abundant, according to the Oregon researchers.

But culturing, or growing, SAR11 in a laboratory so additional study could be conducted was challenging. The research team eventually cultured the organism from water samples taken from the Pacific Ocean off the coast of Oregon.

Two keys to that, explained OSU microbiologist Michael Rappe, lead author of the Nature article, were newly developed procedures that automate and miniaturize the culturing process.

With the sensitive new procedures the researchers were able to mimic the extremely low nutrient content of the bacterium's natural habitat and isolate the tiny bacteria. Eleven cultures, among the smallest free-living cells ever grown in a laboratory, have been cryopreserved, or freeze-dried, for future study.

The significance of the accomplishment goes beyond marine science, according to Giovannoni. He said the inability to culture microorganisms is a pervasive problem that affects study of all the earth's ecosystems.

Bacteria and other simple life forms that have not been cultivated and studied dominate the "bacterioplankton communities" that are the base of the oceans' food and energy chains, the Oregon State microbiologist added.

He noted, as a practical frame of reference, that if all the bacteria in the oceans were put together they would have more biomass than the fishes and marine mammals.