A Comparison of the Rates of Fe(III) Reduction in Synthetic and Bacteriogenic Iron Oxides by Shewanella putrefaciens CN32

The susceptibility of various bacteriogenic iron oxides (BIOS) to bacterial Fe(III) reduction was examined. Reduction resulted in complete dissolution of the iron mineral from the surfaces of the Fe-oxidizing consortium. Reduction rates were compared to that of synthetic ferrihydrite (HFO). The reduction rate of HFO (0.162 day- 1) was significantly lower than that of Aspo (Gallionella dominated) BIOS (0.269 day- 1). Two Canadian (Leptothrix dominated) BIOS samples showed statistically equivalent rates of reduction (0.541 day-1 and 0.467 day- 1), which were higher than both Aspo BIOS and HFO. BIOS produced by different iron-oxidizing genera have different susceptibilities to microbial reduction.