Bacillus selenitireducens is an anaerobic bacterium that grows only weakly as a microaerophile. It is capable of fermentative growth on glucose. This organism respires selenium oxyanions, creating the chemical element selenium. B. selenitireducens lives in bottom sediment, and can be found in many places across the United States, such as in the anoxic mud of Mono Lake, California. This bacterium is gram-positive, forms a short rod, and does not form spores. It is haloalkaliphilic; therefore it requires a hypersaline, alkaline environment, with a pH range of 8.5-10. B. selenitireducens, Sulfospirillum barnesii, and Selenihalanaerobacter shriftii all produce granules on the outside surface of their cell envelope. These granules contain nanospheres of selenium atoms that are arranged into crystalline structures. The nanospheres range from 200-400 nanometers in diameter. They are very complex, and each type of bacteria produce nanospheres with a structure unique to that species of bacteria. This structural variation is most likely due to the vast array of enzymes used during the dissimilatory reduction of selenium. As can be expected, the different nanospheres have different optical densities based on their respective crystalline structures. Researchers at Rensselaer Polytechnic Institute have discovered that these selenium structures exhibit optical and semiconducting properties which are superior to those of current devices synthesized in the laboratory. Since selenium is used in photovoltaic cells and other electronic devices, selenium-forming bacteria have heightened the interest of some researchers. They hope that the ability of these bacteria to produce such unique and complex crystalline selenium nanospheres can be used to create smaller and faster electronic devices. Presently, humans have not been able to synthesize nanostructures that rival these bacterial creations.
REFERENCES
1. Ackerman, Jodi. “Findings of Novel Nanoproperties in Selenium Produced by Bacteria Open New Area of Exploration.” Innovations Report. November 2, 2004. April 20, 2004. http://www.innovationsreport.com/html/reports/interdisciplinary_research/report-25674.html
2. Kalaugher, Liz. “Bacteria Grow Selenium Nanospheres.” Nanotechweb.org February 17, 2004. April 22, 2004. http://nanotechweb.org/articles/news/3/2/9/1
3. Oremland, R.S., Herbel, M.J., Blum, J.S., Langley, S., Beveridge, T.J., Ajayan, P.M., Sutto, T., Ellis, A.V., Curran, S. “Structural and Spectral Features of Selenium Nanospheres Produced by Se-Respiring Bacteria.” 70 (2004): p. 52-60.
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
Return to Missouri S&T Microbiology HomePage Go to DJW's HomePage
This Document is maintained by djwesten@ mst.edu
