Organic solids in soil may speed up bacterial breathing

May 23, 2010

The "mineral-breathing" bacteria found in many oxygen-free environments may be "carbon-breathing" as well.

Oxygen-free, or anaerobic, environments contain microbes sometimes described as "mineral-breathing" because they use iron oxides and other minerals in the same way we use oxygen. According to a study published online May 23 in the journal Nature Geoscience, this bacterial respiration may be accelerated by solid in the soil.

Led by University of Wisconsin-Madison geoscientist Eric Roden, the new work shows that iron oxide-breathing bacteria can do the same with insoluble organic substances, formed when plants and other organic materials biodegrade in soils and sediments. During respiration, the bacteria release that interact with nearby substances, a process called reduction. Reduction of large - called humics and familiar to gardeners as part of planting soil - represents a new pathway for electrical charges to move around in the environment, with implications for understanding soil chemistry and environmental contamination.

"The reason this is so important is that when the humic substances are reduced - that is, when they go from having less electrons to having more electrons - they are very reactive with other things, in particular iron oxides," says Roden, an expert on sediment geochemistry and microbiology.

Iron is both highly reactive and very abundant on Earth, making it a key element for understanding the chemistry, biology, and geology of .

"All kinds of things follow iron oxides - organic contaminants, inorganic contaminants, energy flow, mineral transformations on Earth, speculation about possible iron-based on other worlds," Roden says. Insoluble organic compounds in the soil are a "player in that whole picture that no one had recognized before."

Similar reactions had previously been described with dissolved organic compounds, Roden says, but insoluble ones likely play a larger role in natural environments. "Most of the in soil and sediment is not in solution. It's the gunk at the bottom of the lake, the dirt, the muck in the wetlands."

He and colleagues in Madison and Germany analyzed the insoluble humics by adapting existing techniques, including electron spin resonance and transmission electron microscopy, to confirm that the organic compounds receive electrons from the bacteria and pass them along to iron oxides.

In fact, the electrons shuttle more quickly from the cells to iron oxides when humics are present, Roden says. A group of Dutch scientists recently found electrical currents flowing through marine sediments. Though he has not yet tested the idea, Roden suggests that plant-derived organic compounds could act like wires to enhance the transmission of electrons through soil environments.

"The insoluble humic materials could be an integral part of this previously unrecognized pathway for electrons to move around in sediments," he says. "The bottom line is that reduction of insoluble humics may influence all the kinds of reactions that depend on the oxidation-reduction chemistry in sediments. It's a new twist."

Explore further: US delays decision on Keystone pipeline project

Related Stories

Progress Toward a Biological Fuel Cell?

Dec 30, 2008

(PhysOrg.com) -- Biological fuel cells use enzymes or whole microorganisms as biocatalysts for the direct conversion of chemical energy to electrical energy. One type of microbial fuel cell uses anodes (positive electrodes) ...

Recommended for you

US delays decision on Keystone pipeline project

Apr 18, 2014

The United States announced Friday a fresh delay on a final decision regarding a controversial Canada to US oil pipeline, saying more time was needed to carry out a review.

New research on Earth's carbon budget

Apr 18, 2014

(Phys.org) —Results from a research project involving scientists from the Desert Research Institute have generated new findings surrounding some of the unknowns of changes in climate and the degree to which ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Starblade_Enkai
not rated yet May 23, 2010
First post! LOL!

Aside from that, this is really cool stuff. Do you think this has any use in terms of carbon sequestering?

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...