{"309521":{"#nid":"309521","#data":{"type":"news","title":"Study in \u0027Science\u0027 finds missing piece of biogeochemical puzzle in aquifer","body":[{"value":"\u003Cp\u003E\u003Cem\u003EWritten by Argonne National Laboratory\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003EA study published in Scienceby researchers from the U.S. Department of Energy\u2019s Argonne National Laboratory and co-authored by Georgia Tech may dramatically shift our understanding of the complex dance of microbes and minerals that takes place in aquifers deep underground. This dance affects groundwater quality, the fate of contaminants in the ground and the emerging science of carbon sequestration.\u003C\/p\u003E\u003Cp\u003EDeep underground, microbes don\u2019t have much access to oxygen. So they have evolved ways to breathe other elements, including solid minerals like iron and sulfur.\u003C\/p\u003E\u003Cp\u003EThe part that interests scientists is that when the microbes breathe solid iron and sulfur, they transform them into highly reactive dissolved ions that are then much more likely to interact with other minerals and dissolved materials in the aquifer. This process can slowly but steadily make dramatic changes to the makeup of the rock, soil and water.\u003C\/p\u003E\u003Cp\u003E\u201cThat means that how these microbes breathe affects what happens to pollutants \u2014 whether they travel or stay put \u2014 as well as groundwater quality,\u201d said Ted Flynn, a scientist from Argonne and the \u003Ca href=\u0022https:\/\/www.ci.uchicago.edu\/\u0022\u003EComputation Institute \u003C\/a\u003Eat the \u003Ca href=\u0022http:\/\/www.uchicago.edu\/\u0022\u003EUniversity of Chicago\u003C\/a\u003E and the lead author of the study.\u003C\/p\u003E\u003Cp\u003EAbout a fifth of the world\u2019s population relies on groundwater from aquifers for their drinking water supply, and many more depend on the crops watered by aquifers.\u003C\/p\u003E\u003Cp\u003EFor decades, scientists thought that when iron was present in these types of deep aquifers, microbes who can breathe it would out-compete those who cannot. There\u2019s an accepted hierarchy of what microbes prefer to breathe, according to how much energy each reaction can theoretically yield. (Oxygen is considered the best overall, but it is rarely found deep below the surface.)\u003C\/p\u003E\u003Cp\u003EAccording to these calculations, of the elements that do show up in these aquifers, breathing iron theoretically provides the most energy to microbes. And iron is frequently among the most abundant minerals in many aquifers, while solid sulfur is almost always absent.\u003C\/p\u003E\u003Cp\u003EBut something didn\u2019t add up right. A lot of the microorganisms had equipment to breathe both iron and sulfur. This requires two completely different enzymatic mechanisms, and it\u2019s evolutionarily expensive for microbes to keep the genes necessary to carry out both processes. Why would they bother, if sulfur was so rarely involved?\u003C\/p\u003E\u003Cp\u003EThe team decided to redo the energy calculations assuming an alkaline environment \u2014 \u201cOlder and deeper aquifers tend to be more alkaline than pH-neutral surface waters,\u201d said Argonne coauthor Ken Kemner \u2014 and found that in alkaline environments, it gets harder and harder to get energy out of iron.\u003C\/p\u003E\u003Cp\u003E\u201cBreathing sulfur, on the other hand, becomes even more favorable in alkaline conditions,\u201d Flynn said.\u003C\/p\u003E\u003Cp\u003EThe team reinforced this hypothesis in the lab with bacteria under simulated aquifer conditions. The bacteria, \u003Cem\u003EShewanella oneidensis, \u003C\/em\u003Ecan normally breathe both iron and sulfur. When the pH got as high as 9, however, it could breathe sulfur, but not iron.\u003C\/p\u003E\u003Cp\u003EThere was still the question of where microorganisms like \u003Cem\u003EShewanella\u003C\/em\u003E could find sulfur in their native habitat, where it appeared to be scarce.\u003C\/p\u003E\u003Cp\u003EThe answer came from another group of microorganisms that breathe a different, soluble form of sulfur called sulfate, which is commonly found in groundwater alongside iron minerals. These microbes exhale sulfide, which reacts with iron minerals to form solid sulfur and reactive iron. The team believes this sulfur is used up almost immediately by \u003Cem\u003EShewanella \u003C\/em\u003Eand its relatives.\u003C\/p\u003E\u003Cp\u003E\u201cThis explains why we don\u2019t see much sulfur at any fixed point in time, but the amount of energy cycling through it could be huge,\u201d Kemner said.\u003C\/p\u003E\u003Cp\u003EIndeed, when the team put iron-breathing bacteria in a highly alkaline lab environment without any sulfur, the bacteria did not produce any reduced iron.\u003C\/p\u003E\u003Cp\u003E\u201cThis hypothesis runs counter to the prevailing theory, in which microorganisms compete, survival-of-the-fittest style, and one type of organism comes out dominant,\u201d Flynn said. Rather, the iron-breathing and the sulfate-breathing microbes depend on each other to survive.\u003C\/p\u003E\u003Cp\u003EUnderstanding this complex interplay is particularly important for sequestering carbon. The idea is that in order to keep harmful carbon dioxide out of the atmosphere, we would compress and inject it into deep underground aquifers. In theory, the carbon would react with iron and other compounds, locking it into solid minerals that wouldn\u2019t seep to the surface.\u003C\/p\u003E\u003Cp\u003EIron is one of the major players in this scenario, and it must be in its reactive state for carbon to interact with it to form a solid mineral. Microorganisms are essential in making all that reactive iron. Therefore, understanding that sulfur\u2014and the microbe junkies who depend on it\u2014plays a role in this process is a significant chunk of the puzzle that has been missing until now.\u003C\/p\u003E\u003Cp\u003EThe study, \u201cSulfur-Mediated Electron Shuttling During Bacterial Iron Reduction,\u201d appeared online in the May 1 edition of \u003Cem\u003EScience Express\u003C\/em\u003E and was published in \u003Cem\u003EScience\u003C\/em\u003E earlier this summer. Other authors on the study were Argonne scientists Bhoopesh Mishra (also of the Illinois Institute of Technology) and Edward O\u2019Loughlin and \u003Ca href=\u0022http:\/\/www.gatech.edu\/\u0022\u003EGeorgia Tech\u003C\/a\u003E scientist Thomas DiChristina.\u003C\/p\u003E\u003Cp\u003E\u201cThe exciting findings reported in our study were made possible by combining the microbiology expertise of my laboratory in the School of Biology at Georgia Tech with the geochemical expertise of the Molecular Environmental Sciences group led by Ken Kemner at Argonne National Laboratory,\u201d said Professor DiChristina, \u201cThe biogeochemical link between bacterial iron- and sulfur-breathing bacteria is important for survival of microbial communities in modern subsurface environments, and also provides clues to the evolution of ancient metabolic processes on an early Earth that lacked oxygen but contained large amounts of iron\u0026nbsp;and sulfur.\u201d\u003C\/p\u003E\u003Cp\u003EFunding for the research was provided by the \u003Ca href=\u0022http:\/\/science.energy.gov\/\u0022\u003EU.S. Department of Energy\u2019s Office of Science\u003C\/a\u003E. The \u003Ca href=\u0022http:\/\/www.aps.anl.gov\/\u0022\u003EAdvanced Photon Source\u003C\/a\u003E (APS) is also supported by the DOE\u2019s Office of Science. The team conducted X-ray analysis at the APS \u003Ca href=\u0022https:\/\/gsecars.uchicago.edu\/\u0022\u003EGeoSoilEnviroCARS\u003C\/a\u003E beamline 13-ID-E, which is operated by the University of Chicago and jointly supported by the \u003Ca href=\u0022http:\/\/www.nsf.gov\/\u0022\u003ENational Science Foundation\u003C\/a\u003E and the DOE\u2019s Office of Science. Additional support came from the \u003Ca href=\u0022http:\/\/www.nih.gov\/\u0022\u003ENational Institutes of Health\u003C\/a\u003E and the National Science Foundation.\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022https:\/\/www.ci.uchicago.edu\/\u0022\u003E\u003Cstrong\u003ET\u003C\/strong\u003E\u003Cstrong\u003E\u202a\u003C\/strong\u003E\u003Cstrong\u003Ehe Computation Institute \u003C\/strong\u003E\u003C\/a\u003E(CI), a joint institute of the University of Chicago and Argonne National Laboratory, is an intellectual nexus for scientists and scholars pursuing multi-disciplinary research, and a resource center for developing and applying innovative computational approaches. Founded in 1999, it is home to over 200 faculty, fellows, and staff researching complex, system-level problems in such areas as biomedicine, energy and climate, astronomy and astrophysics, computational economics, social sciences and molecular engineering. CI is home to diverse projects including the\u003Ca href=\u0022https:\/\/rdcep.org\/\u0022\u003ECenter for Robust Decision Making on Climate and Energy Policy\u003C\/a\u003E, the \u003Ca href=\u0022http:\/\/cmts.uchicago.edu\/\u0022\u003ECenter for Multiscale Theory and Simulation\u003C\/a\u003E, the \u003Ca href=\u0022https:\/\/urbanccd.org\/\u0022\u003EUrban Center for Computation and Data\u003C\/a\u003E and \u003Ca href=\u0022https:\/\/www.globus.org\/\u0022\u003EGlobus\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EThe Advanced Photon Source\u003C\/strong\u003E at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy\u2019s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security. To learn more about the Office of Science X-ray user facilities, visit the \u003Ca href=\u0022http:\/\/science.energy.gov\/user-facilities\/basic-energy-sciences\/\u0022\u003Euser facilities directory\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EArgonne National Laboratory\u003C\/strong\u003E seeks solutions to pressing national problems in science and technology. The nation\u0027s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America\u0027s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by \u003Ca href=\u0022http:\/\/www.uchicagoargonnellc.org\/\u0022\u003EUChicago Argonne, LLC\u003C\/a\u003E for the U.S. Department of Energy\u0027s Office of Science.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EDOE\u2019s Office of Science\u003C\/strong\u003E is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, visit \u003Ca href=\u0022http:\/\/science.energy.gov\/\u0022\u003Escience.energy.gov\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EStudy may dramatically shift our understanding of the complex dance of microbes and minerals that takes place in aquifers deep underground. This dance affects groundwater quality, the fate of contaminants in the ground and the emerging science of carbon sequestration.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"New study may dramatically shift our understanding of the complex dance of microbes and minerals that takes place in aquifers deep underground."}],"uid":"27560","created_gmt":"2014-07-18 13:09:09","changed_gmt":"2016-10-08 03:16:48","author":"Jason Maderer","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2014-07-18T00:00:00-04:00","iso_date":"2014-07-18T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"100761":{"id":"100761","type":"image","title":"Thomas DiChristina","body":null,"created":"1449178159","gmt_created":"2015-12-03 21:29:19","changed":"1475894717","gmt_changed":"2016-10-08 02:45:17"}},"media_ids":["100761"],"groups":[{"id":"1214","name":"News Room"}],"categories":[],"keywords":[],"core_research_areas":[{"id":"39441","name":"Bioengineering and Bioscience"}],"news_room_topics":[{"id":"71911","name":"Earth and Environment"},{"id":"71881","name":"Science and Technology"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJason Maderer\u003Cbr \/\u003ENational Media Relations\u003Cbr \/\u003E404-385-2966\u003Cbr \/\u003E\u003Ca href=\u0022mailto:maderer@gatech.edu\u0022\u003Emaderer@gatech.edu\u003C\/a\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["maderer@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}