Microbes Beneath Sea Floor Genetically Distinct

Tiny microbes beneath the sea floor, distinct from life on the Earth's surface, may account for one-tenth of the Earth's living biomass, according to an interdisciplinary team of researchers, but many of these minute creatures are living on a geologic timescale.

The researchers, who included Biddle; House; Stephan C. Schuster, associate professor; and Jean E. Brenchley, professor, biochemistry and molecular biology, Penn State; and Sorel Fitz-Gibbon, assistant research molecular biologist at the Center for Astrobiology, UCLA, found that a large percentage of the microbes were Archaea, single-celled organisms that look like Bacteria but are different on the metabolic and genetic levels. The percentage of Archaea increases with depth so that at 164 feet below the sea floor, perhaps 90 percent of the microbes are Archaea. The total number of organisms decreases with depth, but there are lots of cells, perhaps as many as 1,600 million cells in each cubic inch.

If the rest of the world is like the Peruvian Margin, then at least one tenth and as much as a third of the Earth's biomass could be these tiny microbes living in the mud. However, this population lives at an unusual rate. Single-celled organisms usually consume food for energy and then rather than grow larger, simply divide and reproduce themselves. While the Bacteria Escherichia Coli, as an example, doubles its numbers every 20 minutes, these Archaea double on the order of hundreds or thousands of years and consume very little energy.

"In essence, these microbes are almost, practically dead by our normal standards," says House. "They metabolize a little, but not much."

Biddle notes that these microbes could survive major Earth impacts by asteroids, so the subsea floor could be a refuge for life during extinction events. Now this study shows they may be a reservoir of novel genetic material as well. Her future research will focus on understanding the lifestyle of the microbes.

"For example, how do they die?" asks Biddle. "It is a simple question that we cannot answer."

These organisms could comprise a tenth of all the biomass on Earth and we don't even know how they die. Amazing.

The bottom of the ocean is the greatest area for exploration out there and the more scientists checking it out the better.

via Science Daily