"We used to believe that microbes only consumed methane in marine anaerobic sediment if sulfate was present," said Emily Beal, graduate student in geoscience, Penn State. "But other electron acceptors, such as iron and manganese, are more energetically favorable than sulfate."
Beal, working with Christopher H. House, associate professor of geoscience, Penn State, and Victoria J. Orphan, assistant professor of geobiology, California Institute of Technology, incubated a variety of marine sediments to determine if there were microbes that could convert methane to carbon dioxide without using any sulfur compounds. They report their results in today's (July 10) issue of Science.
Using samples of marine sediment taken 20 miles off the California coast and about 1,800 feet deep near methane seeps in the Pacific, Beal incubated a variety of sediment systems including as controls, an autoclaved sterile sample, a sample with sulfate as a control and a sample that was sulfate, iron oxide and manganese oxide free, but live. She also incubated samples that were sulfate free but contained iron oxide or manganese oxide. She placed methane gas that contained the non-radioactive carbon-13 isotope in the empty space in the flasks above the sediment and tested any resulting carbon dioxide produced by the samples. All the carbon dioxide had the carbon-13 isotope and so came from the methane samples.The sterile control showed no activity, while the live control without sulfate showed minute activity. The sulfate control showed the most activity as expected, but both the iron and manganese oxide-laced samples showed activity, although less activity than the sulfate.
One reason they are important is that some of the carbon dioxide produced reacts with both the manganese and iron to form carbonates that precipitate and sequester carbon in the oceans. Even if the carbon dioxide escaped into the atmosphere, it is a less problematic greenhouse gas than methane.
On the early Earth, where oxygen was absent from the atmosphere, sulfates were scarce. Without sulfates, iron and manganese oxides may have been essential in converting methane to carbon dioxide.
"Sulfate comes mostly from oxidative weathering of rocks," said Beal. "Oxygen is needed for this to occur."
While manganese and iron oxides are made in today's oxygen atmosphere, they where also formed by photochemical reactions in a low oxygen atmosphere. These oxides were probably more abundant in the early Earth's oceans than sulfates.
While Beal has categorized the more than a dozen microorganisms living in the sediments she used, she does not know which of these microbes is responsible for consuming methane. It might be one bacteria or archaea species, or it may be a consortium of microbes. She is trying to identify the organisms responsible.
The National Science Foundation and the NASA Astrobiology Institute supported this work.
A'ndrea Elyse Messer | EurekAlert!
Newly designed molecule binds nitrogen
23.02.2018 | Julius-Maximilians-Universität Würzburg
Atomic Design by Water
23.02.2018 | Max-Planck-Institut für Eisenforschung GmbH
A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.
By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...
Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
23.02.2018 | Life Sciences
23.02.2018 | Earth Sciences
23.02.2018 | Materials Sciences