Microbes are living more than 500 feet beneath the seafloor in 5-million-year-old sediment, according to new findings by researchers at the University of Delaware (UD) and Woods Hole Oceanographic Institution (WHOI). Genetic material in mud from the bottom of the ocean — called the deep biosphere —revealed an ecosystem of active bacteria, fungi, and other microscopic organisms at depths deeper than a skyscraper is high. The findings were published online in Nature on June 12, 2013. “This type of examination shows active cells,” said co-author Dr. Jennifer F. Biddle, assistant professor of marine biosciences in UD’s College of Earth, Ocean, and Environment. “We knew that all of these cells were buried, but we didn’t know if they were doing anything.” In fact, the microbes are reproducing, digesting food, and even moving around despite the extreme conditions found there: little to no oxygen, heavy pressure, and minimal nutrient sources. The organisms could shed light on how carbon and other elements circulate in the environment, the scientists reported. The researchers analyzed messenger RNA (mRNA) in sediment from different depths collected off the coast of Peru in 2002 during Leg 201 of the Ocean Drilling Program. This first glimpse into the workings of the heretofore hidden ecosystem was made possible by the first successful extraction of total mRNA, or the “metatranscriptome,” from the deep biosphere. mRNA is highly sought-after by microbial ecologists because its presence indicates that the cells that made it are alive and because it carries the instructions for the proteins the cells are making. But because the metabolic rates in the deep biosphere are very low and mRNA is present in small amounts, extracting enough of it to analyze from deep sediments had been thought by many scientists to be impossible.
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