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Aquatic microbe oxidizes iron minerals from the surface inward

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Posted June 28, 2013
Microbial proteins shuttle electrons out of iron particles, oxidizing iron from Fe(II) to Fe(III). This study provides insights into reactions that affect both iron cycling in the environment and its biogeochemical linkage to carbon cycling, as well as biotechnologies.

Microbial proteins shuttle electrons out of iron particles, oxidizing iron from Fe(II) to Fe(III). This study provides insights into reactions that affect both iron cycling in the environment and its biogeochemical linkage to carbon cycling, as well as biotechnologies.

When the water-dwelling microbe Sideroxydans lithotrophicus ES-1 connects with iron mineral particulates, three microbial proteins quickly extract electrons from divalent iron or Fe(II), leaving behind trivalent iron, according Pacific Northwest National Laboratory and Lawrence Berkeley National Laboratory scientists. The oxidation reaction begins when the protein contacts the particle’s surface and continues into the particle interior, without damaging the iron lattice. The electron transfer is faster if the particle starts with a high ratio of Fe(II) to Fe(III).

 

“Using a new experimental strategy of probing iron nanoparticles interacting with pure protein, we proved that proteins can efficiently oxidize the iron in the interior without changing the structure,” said Dr. Juan Liu, a PNNL geochemist who led the year-long study. “Before, we didn’t have the tools and methods to directly investigate Fe(II) minerals and their interactions with proteins. Now, we do.”

Iron is continually transformed by microbes in the subsurface environment. Soluble Fe(II), which travels through the groundwater, can become Fe(III), which remains relatively stationary. By understanding how the microorganisms accelerate or control iron’s changes, scientists better understand how microbial activity is linked to iron cycling in the environment. This understanding also helps shed light onto processes coupled to the iron cycle, such as cycling of carbon, nitrogen, sulfur, and other metals. For example, this connection could be important for predicting how subsurface biogeochemistry contributes to carbon exchange with near-surface environments, with impacts on processes that influence food availability, water resources, and extreme weather patterns.

Read more at: Phys.org

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