Organic solids in soil may accelerate bacterial breathing

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London, May 24 (ANI): Organic solids in soil may speed up bacterial breathing, a new study has found.

Led by University of Wisconsin-Madison geoscientist Eric Roden, the new research shows that iron oxide-breathing bacteria can also 'mineral-breathe' with insoluble organic substances, formed when plants and other organic materials biodegrade in soils and sediments.

During respiration, the bacteria release electrons that interact with nearby substances, a process called reduction.

Reduction of large organic molecules - 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.

Roden said: "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,"

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

Roden said: "All kinds of things follow iron oxides - organic contaminants, inorganic contaminants, energy flow, mineral transformations on Earth, speculation about possible iron-based microbial life on other worlds."

Insoluble organic compounds in the soil are a "player in that whole picture that no one had recognized before."

According to Roden, similar reactions had previously been described with dissolved organic compounds, but insoluble ones likely play a larger role in natural environments.

He said: "Most of the organic material 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 analysed 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 pointed out.

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.

Roden said: "The insoluble humic materials could be an integral part of this previously unrecognised pathway for electrons to move around in sediments."

He added: "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."

The study has appeared online May 23 in the journal Nature Geoscience. (ANI)

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