Dissolution Morphology of Iron (Oxy)(Hydr)Oxides Exposed to the Dissimilatory Iron-Reducing Bacterium Shewanella oneidensis MR-1

Abstract

Atomic force microscopy was used to compare the dissolution morphology of iron (oxy)(hydr)oxide coated slides exposed to the dissimilatory iron reducing bacterium Shewanella oneidensis MR-1 and a Type II protein secretion mutant unable to reduce iron minerals without an exogenous electron shuttle. Dissolution morphologies of slides exposed to the wild-type organism were heterogeneous and consistent with the morphology of bacterial microcolonies observed by confocal microscopy. In contrast, dissolution morphologies of slides exposed to wild-type or mutant strains and the electron shuttling compound 9,10-anthraquinone-2,6-disulfonate were homogeneous. These results suggest that microcolony formation by the wild-type strain may limit dissolution whereas respiration using the shuttle compound relieves this limitation.

Keywords:

• microbial iron reduction
• dissolution morphology
• deltagspD
• Shewanella oneidensis
• AQDS

The authors are grateful for the assistance of Professor Angus Wilkinson for performing the X-ray diffraction measurement on the iron (oxy)(hydr)oxide samples. The confocal microscopy experiments were conducted at the Flow Cytometry and Confocal Microscopy Core Laboratory at Georgia Institute of Technology with the help of Johnafel Crowe. Finally, we wish to thank Ms. Meg Camille Grantham for her helpful suggestions regarding slide preparation. This work was funded by the U.S. National Science Foundation and Department of Energy.