Navigation Links
Study in Science finds missing piece of biogeochemical puzzle in aquifers
Date:5/1/2014

A study published today in Science by researchers from the U.S. Department of Energy's Argonne National Laboratory 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.

Deep underground, microbes don't have much access to oxygen. So they have evolved ways to breathe other elements, including solid minerals like iron and sulfur.

The 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.

"That means that how these microbes breathe affects what happens to pollutantswhether they travel or stay putas well as groundwater quality," said Ted Flynn, a scientist from Argonne and the Computation Institute at the University of Chicago and the lead author of the study.

About a fifth of the world's population relies on groundwater from aquifers for their drinking water supply, and many more depend on the crops watered by aquifers.

For 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's 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.)

According 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.

But something didn't 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's evolutionarily expensive for microbes to keep the genes necessary to carry out both processes. Why would they bother, if sulfur was so rarely involved?

The team decided to redo the energy calculations assuming an alkaline environment"Older and deeper aquifers tend to be more alkaline than pH-neutral surface waters," said Argonne coauthor Ken Kemnerand found that in alkaline environments, it gets harder and harder to get energy out of iron.

"Breathing sulfur, on the other hand, becomes even more favorable in alkaline conditions," Flynn said.

The team reinforced this hypothesis in the lab with bacteria under simulated aquifer conditions. The bacteria, Shewanella oneidensis, can normally breathe both iron and sulfur. When the pH got as high as 9, however, it could breathe sulfur, but not iron.

There was still the question of where microorganisms like Shewanella could find sulfur in their native habitat, where it appeared to be scarce.

The 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 Shewanella and its relatives.

"This explains why we don't see much sulfur at any fixed point in time, but the amount of energy cycling through it could be huge," Kemner said.

Indeed, when the team put iron-breathing bacteria in a highly alkaline lab environment without any sulfur, the bacteria did not produce any reduced iron.

"This hypothesis runs counter to the prevailing theory, in which microorganisms compete, survival-of-the-fittest style, and one type of organism comes out dominant," Flynn said. Rather, the iron-breathing and the sulfate-breathing microbes depend on each other to survive.

Understanding 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't seep to the surface.

Iron 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 sulfurand the microbe junkies who depend on itplays a role in this process is a significant chunk of the puzzle that has been missing until now.

The study, "Sulfur-Mediated Electron Shuttling During Bacterial Iron Reduction," appears online today in the May 1 edition of Science Express and will be published in Science at the end of the month. Other authors on the study were Argonne scientists Bhoopesh Mishra (also of the Illinois Institute of Technology) and Edward O'Loughlin and Georgia Tech scientist Thomas DiChristina.


'/>"/>

Contact: Brian Grabowski
bgrabowski@anl.gov
630-252-1232
DOE/Argonne National Laboratory
Source:Eurekalert

Related biology news :

1. Study by UC Santa Barbara researchers suggests that bacteria communicate by touch
2. Law that regulates shark fishery is too liberal: UBC study
3. New study will help protect vulnerable birds from impacts of climate change
4. Study jointly led by UCSB researcher supports theory of extraterrestrial impact
5. BYU study: Using a gun in bear encounters doesnt make you safer
6. 15-year study: When it comes to creating wetlands, Mother Nature is in charge
7. Pycnogenol (French maritime pine bark extract) shown to improve menopause symptoms in new study
8. Crystal structure of archael chromatin clarified in new study
9. EU-funded study underlines importance of Congo Basin for global climate and biodiversity
10. University of Houston study shows BP oil spill hurt marshes, but recovery possible
11. Study demonstrates cells can acquire new functions through transcriptional regulatory network
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/15/2016)... 15, 2016  A new partnership announced today ... underwriting decisions in a fraction of the time ... and high-value life insurance policies to consumers without ... With Force Diagnostics, rapid testing (A1C, Cotinine and ... (blood pressure, weight, pulse, BMI, and activity data) ...
(Date:3/31/2016)... 2016   LegacyXChange, ... "Company") LegacyXChange is excited to release its ... to be launched online site for trading 100% guaranteed ... will also provide potential shareholders a sense of the ... an industry that is notorious for fraud. The video ...
(Date:3/22/2016)... PUNE, India , March 22, 2016 ... new market research report "Electronic Sensors Market for ... Fingerprint, Proximity, & Others), Application (Communication & ... and Geography - Global Forecast to 2022", ... consumer industry is expected to reach USD ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... --  Ginkgo Bioworks , a leading organism design ... awarded as one of the World Economic Forum,s ... innovative companies. Ginkgo Bioworks is engineering biology to ... in the nutrition, health and consumer goods sectors. ... including Fortune 500 companies to design microbes for ...
(Date:6/24/2016)... June 24, 2016 Epic Sciences unveiled ... cancers susceptible to PARP inhibitors by targeting homologous ... (CTCs). The new test has already been incorporated ... multiple cancer types. Over 230 clinical ... response pathways, including PARP, ATM, ATR, DNA-PK and ...
(Date:6/24/2016)... ... , ... Researchers at the Universita Politecnica delle Marche in Ancona combed medical ... mesothelioma. Their findings are the subject of a new article on the Surviving Mesothelioma ... in the blood, lung fluid or tissue of mesothelioma patients that can help point ...
(Date:6/23/2016)... Wausau, WI (PRWEB) , ... June 23, 2016 ... ... probiotic supplements, is pleased to announce the launch of their brand, UP4™ Probiotics, ... supplements for over 35 years, is proud to add Target to its list ...
Breaking Biology Technology: