An interesting article published online at the Proceedings of the National Academy of Sciences of the United States of America (PNAS) demonstrates formation of arsenic-sulfide nanotubes by the metal-reducing bacterium Shewanella sp. HN-41.


Here is a link to the paper...


Ji-Hoon Lee, Min-Gyu Kim, Bongyoung Yoo, Nosang V. Myung, Jongsun Maeng, Takhee Lee, Alice C. Dohnalkova, James K. Fredrickson, Michael J. Sadowsky, and Hor-Gil Hur. Biogenic formation of photoactive arsenic-sulfide nanotubes by Shewanella sp. strain HN-41. Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0707595104

Abstract:
Microorganisms facilitate the formation of a wide range of minerals that have unique physical and chemical properties as well as morphologies that are not produced by abiotic processes. Here, we report the production of an extensive extracellular network of filamentous, arsenic-sulfide (As-S) nanotubes (20100 nm in diameter by (approx) 30 m in length) by the dissimilatory metal-reducing bacterium Shewanella sp. HN-41. The As-S nanotubes, formed via the reduction of As(V) and S2OFormula, were initially amorphous As2S3 but evolved with increasing incubation time toward polycrystalline phases of the chalcogenide minerals realgar (AsS) and duranusite (As4S). Upon maturation, the As-S nanotubes behaved as metals and semiconductors in terms of their electrical and photoconductive properties, respectively. The As-S nanotubes produced by Shewanella may provide useful materials for novel nano- and opto-electronic devices.