Indirect Oxidation of Co(II) in the Presence of the Marine Mn(II)-Oxidizing Bacterium Bacillus sp. Strain SG-1

Abstract

Cobalt(II) oxidation in aquatic environments has been shown to be linked to Mn(II) oxidation, a process primarily mediated by bacteria. This work examines the oxidation of Co(II) by the spore-forming marine Mn(II)-oxidizing bacterium Bacillus sp. strain SG-1, which enzymatically catalyzes the formation of reactive nanoparticulate Mn(IV) oxides. Preparations of these spores were incubated with radiotracers and various amounts of Co(II) and Mn(II), and the rates of Mn(II) and Co(II) oxidation were measured. Inhibition of Mn(II) oxidation by Co(II) and inhibition of Co(II) oxidation by Mn(II) were both found to be competitive. However, from both radiotracer experiments and X-ray spectroscopic measurements, no Co(II) oxidation occurred in the complete absence of Mn(II), suggesting that the Co(II) oxidation observed in these cultures is indirect and that a previous report of enzymatic Co(II) oxidation may have been due to very low levels of contaminating Mn. Our results indicate that the mechanism by which SG-1 oxidizes Co(II) is through the production of the reactive nanoparticulate Mn oxide.

Coexistence of Fe(II)- and Mn(II)-oxidizing bacteria govern the formation of deep sea umber deposits

“…Mn signals are primarily correlated with Ca, probably due to uptake from sea water during crystallization of a Mn oxide phase . The elevated 59 Co signals are correlated with Mn and Fe signals, suggesting that Co is probably formed through the adsorption of Co onto Mn oxides (Murray et al, 2007) or Fe oxyhydroxides.…”

Distribution and speciation of trace elements in iron and manganese oxide cave deposits

“…Substantial quantities of Co are taken up by synthetic Mn oxides and Co is often enriched in marine and soil ferromanganese nodules, and in surface stream Mn oxide coatings (Burns, 1976;Carpenter and Hayes, 1980;Cerling and Turner, 1982;Dillard and Crowther, 1982;Crowther and Dillard, 1983;Manceau et al, 1997;Takahashi et al, 2007). The oxidation of Co(II) is often closely correlated with microbial Mn(II) oxidation (Lee and Tebo, 1994) but there is clear evidence that Co(II) oxidation is not microbially mediated but rather abiotically initiated by the Mn(IV) microbial product (Murray et al, 2007). The scavenging of Co from surface streams by Mn oxide gravel coatings (Carpenter and Hayes, 1980;Cerling and Turner, 1982) and the high concentrations of Co found in subsurface Mn oxide cave stream pebble coatings (White et al, 2009;Frierdich et al, 2011) suggests that Mn oxides in cave systems inhibit Co transport and availability within karst aquifers.…”

Fungal Mn oxides supporting Mn(II) oxidase activity as effective Mn(II) sequestering materials

“…[1,3] Along with their high sorption capacity, BMOs have a strong ability to oxidize various redox-sensitive elements (e.g. As(III) to As(V), [4] Cr(III) to Cr(IV), [5] Co(II) to Co(III), [6,7] Ce(III) to Ce(IV), [8,9] etc.). Thus, by forming BMOs, Mn(II)-oxidizing microorganisms have a significant impact on the geochemical fate of various elements in the environment.…”