Ocean Microbe Census Discovers Diverse World of Rare Bacteria

A startling revelation about the number of different kinds of bacteria in the deep-sea raises fundamental new questions about microbial life and evolution in the oceans.

In a paper published in the USA by the Proceedings of the National Academy of Sciences Journal (July 31, online early edition), scientists reveal marine microbial diversity may be some 10 to 100 times more than expected, and the vast majority are previously unknown, low-abundance organisms theorized to play an important role in the marine environment as part of a “rare biosphere.”

“These observations blow away all previous estimates of bacterial diversity in the ocean,” says lead author Mitchell L. Sogin, director of the Marine Biological Laboratory (MBL)'s Josephine Bay Paul Center for Comparative and Molecular Biology and Evolution, located in Woods Hole, Massachusetts.

“Microbiologists have formally described 5,000 microbial 'species',” he says. “This study shows we have barely scratched the surface. Over the last 10 to 20 years, molecular studies have shown there to be more than 500,000 kinds of micro organisms. In our new study, we discovered more than 20,000 in a single liter (about one quart) of seawater, having expected just 1,000 to 3,000.”