(Newswise)–Microbes are everywhere — in humans they protect us from harmful bacteria and help us digest food; in soils, they provide nutrients and encourage growth of plants. Microbes even live in sediments below the seafloor where they play a key role in the underwater ecosystem. Scientists are identifying and characterizing more microbes each year using DNA sequencing technologies. As each new species is sequenced, scientists add it to the microbial “tree of life,” creating a virtual census of what’s there. Turns out it’s not an easy job. To put things in perspective, scientists aren’t sure how many microbes even exist. Estimates vary widely from millions to trillions. University of Delaware professor Jennifer Biddle and Rosa Leon-Zayas, who completed post-doctoral work at UD earlier this year, recently described new details about microbes known as Parcubacteria in a paper published in Environmental Microbiology. The Parcubacteria were found in sediment samples collected by James Cameron within the Challenger Deep region of the Mariana Trench during the Deepsea Challenge Expedition. Leon-Zayas’ doctoral advisor, Doug Bartlett at Scripps Institution of Oceanography, was a chief scientist on the expedition. “From a scientific perspective, Challenger Deep was an invaluable opportunity to collect samples from the deepest part of the ocean,” said Leon-Zayas, the paper’s lead author, now an assistant professor at Willamette University.