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

Abstract

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 Äspö (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 Äspö BIOS and HFO. BIOS produced by different iron-oxidizing genera have different susceptibilities to microbial reduction.

Keywords:

• BIOS
• ferrihydrite
• iron reduction
• Shewanella putrefaciens

SL was supported by scholarships from the Natural Sciences and Engineering Research Council of Canada (NSERC), the Ontario Graduate Scholarship (OGS) program, and the University of Ottawa. Chalk River samples were obtained as part of an NSERC Strategic Project grant awarded to GF. Special thanks go to Dr. Kartsen Pedersen (University of Gothenburg, Sweden), for hosting DF and providing us with samples of Äspö BIOS. We thank Dr. Susan Glasauer (University of Guelph, Canada) for her critical review of the manuscript. The authors are also grateful to Dragica Bogdanovic (National HIV and Retrovirology Laboratories, Health Canada) for her assistance with sample irradiation, to Dianne Moyles and Bob Harris (Department of Molecular and Cellular Biology, University of Guelph, Canada), for their assistance with the TEM, and to Xavier Châtellier (Géosciences, Université de Rennes, France) for his assistance with SEM.

Notes

^a Putative identifications, based on distinct cellular morphologies.

^a No potential matches seen in the XRD patterns from BIOS.

^a Based on increases in the ratio of Fe(II):total Fe.

^b No significant difference (p < 0.05).