Blacksburg, Va., Sept. 13, 2006 -- One of the most common bacteria in the Earth, Shewanella oneidensis MR-1, uses oxygen as an energy source for respiration. But in the absence of oxygen, Shewanella uses (oxy)hydroxide minerals. These metal particles may also have adsorbed heavy metals on them. As a result, Shewanella influence the mobility and bioavailability of iron and environmental contaminants like lead, cobalt, and arsenic.

Ph.D. student Saumyaditya Bose and Professor Michael Hochella Jr., both in geosciences in the College of Science at Virginia Tech, and their research colleagues at Pacific Northwest National Laboratory (PNNL), are looking at how the size of iron oxide nano particles influences the bacteria's ability to breathe. This is the first study by any group that couples environmental microbiology and nano-mineralogy.

"This adds to our understanding of how nanoparticles might influence the environment and contaminant metal mobility in our rivers, lakes and other surface waters, as well as groundwater," said Bose.

He will present the research at the 232nd National Meeting of the American Chemical Society on September 10-14 in San Francisco.

Using iron oxide nanoparticles (less than 100 nm), which are common and the most used transition metal oxide for bacterial respiration, the researchers are looking at the interfacial reactions between the whole bacterial cell and the particles to determine the influence of mineral size on microbial reduction rates at the nanoscale. The researchers are looking at microbial reduction of nano hematite, which Bose synthesized in the lab and characterized.

"Nano particles of iron oxides are present everywhere and, due to their small size but large surface area, they provide bacteria a large amount of reactive sites," said Bose. "These particles are reduced by biological and non-biological methods. Different metals, including toxic heavy meals, are adsorbed onto these
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Contact: Susan Trulove
STrulove@vt.edu
540-231-5646
Virginia Tech
13-Sep-2006