Showing papers by "Danielle Fortin published in 2012"
TL;DR: Iron sulfides in the bulk phase were common in all assays, but specific aluminum precipitates formed in close association with cell surfaces and may function as a detoxification mechanism of dissolved Al species at low pH.
50 citations
TL;DR: In this paper, the authors focus on the microbial community structure of iron oxyhydroxide minerals that often occur in tight association with microbial life, referred to as Biogenic Iron Oxyhydroxides (BIOS).
Abstract: Over the last decade or so, several studies have investigated the formation, mineralogy and microbial composition of iron oxyhydroxides. Here, we focus on the exploration of the microbial community structure of iron oxyhydroxide minerals that often occur in tight association with microbial life, which are referred to as Biogenic Iron Oxyhydroxides (BIOS). BIOS deposits host a wide range of microbial taxa usually found living in the oxic, suboxic and anaerobic interfaces of the biogeosphere. These organisms are responsible for the global cycling of Fe, N, C and S. Near the surface of BIOS mats, O2 at ambient atmospheric levels rapidly reacts with dissolved Fe(II) to form insoluble Fe(III) minerals. Due to the activity of highly efficient heterotrophic O2 respirers, BIOS biofilms usually transit from the top to the bottom (within a mm range) into a suboxic zone where microaerophilic iron-oxidizing bacteria thrive, transforming Fe(II) to Fe(III), while generating organic carbon. The bulk of the Fe(III), prod...
29 citations
TL;DR: In this paper, changes in the mineralogy, microbial community structure and aquatic geochemistry of bacteriogenic iron oxides (BIOS) deposited at a circumneutral groundwater seep were recorded seasonally.
Abstract: Changes in the mineralogy, microbial community structure and aquatic geochemistry of bacteriogenic iron oxides (BIOS) deposited at a circumneutral groundwater seep were recorded seasonally. X-ray diffraction and X-ray absorption spectroscopy demonstrated that 2-line ferrihydrite dominated the iron-bearing mineralogy of the BIOS (>60%). Minor proportions of the more crystalline lepidocrocite were also detected in BIOS collected throughout the year (<30%), but goethite (<15%) was only identified in sediments collected during the spring, summer and fall months. Subsurface porewater profiles generally showed an increase in dissolved equilibrium concentrations of Fe(II), indicative of microbial Fe(III) reduction, and the depth at which appreciable levels of dissolved Fe(II) (and to a lesser extent manganese) arose, and sulfate concentrations declined, become shallower as the seasons progressed from spring to fall. Clone libraries constructed from 16S rRNA gene sequence analysis of surficial BIOS showed the pre...
25 citations
TL;DR: In this paper, the authors measured HFO particles in samples of natural bacteriogenic iron oxides (BIOS) from three contrasting field sites: the Loihi Seamount (southern Hawaii); Aspo Hard Rock Laboratory (eastern Sweden); and Chalk River Laboratories (northern Canada) representing seafloor saline, underground brackish, and surface freshwater aqueous conditions.
Abstract: Helical stalks (resembling Gallionella ferruginea, Mariprofundus ferrooxydans) and filamentous sheaths (resembling Leptothrix ochracea) of Fe2+-oxidizing bacteria (FeOB) are mineralized by hydrous ferric oxides (HFO). To perform both inter-species and inter-site size comparisons of HFO particles on stalks and sheaths we measured HFO particles in samples of natural bacteriogenic iron oxides (BIOS) from 3 contrasting field sites: the Loihi Seamount (southern Hawaii); Aspo Hard Rock Laboratory (eastern Sweden); and Chalk River Laboratories (northern Canada) representing seafloor saline, underground brackish, and surface freshwater aqueous conditions. Ambient temperatures were in the psychrophilic range and pHs measured for Loihi, CRL, and Aspo were 5.6, 6.9 and 7.4, respectively. Dissolved Fe was lowest for CRL (0.2 mg · L−1) followed by Aspo (1.5 mg · L−1), then Loihi (4.5–14.9 mg · L−1). L. ochraceasheaths appear to have surface properties that restrict HFO particle growth in comparison to G.ferruginea-M.f...
11 citations