A Comparison of the Sorption Reactivity of Bacteriogenic and Mycogenic Mn Oxide Nanoparticles

Biogenic MnO₂ minerals affect metal fate and transport in natural and engineered systems by strongly sorbing metals ions. The ability to produce MnO₂ is widely dispersed in the microbial tree of life, leading to potential differences in the minerals produced by different organisms. In this study, we compare the structure and reactivity of biogenic Mn oxides produced by the biofilm-forming bacterium <i>Pseudomonas putida</i> GB-1 and the white-rot fungus <i>Coprinellus</i> sp. The rate of Mn­(II) oxidation, and thus biomineral production, was 45 times lower for <i>Coprinellus</i> sp. (5.1 × 10^–2 mM d^–1) than for <i>P. putida</i> (2.32 mM d^–1). Both organisms produced predominantly Mn­(IV) oxides with hexagonal-sheet symmetry, low sheet stacking, small particle size, and Mn­(II/III) in the interlayer. However, we found that mycogenic MnO₂ could support a significantly lower quantity of Ni sorbed via inner-sphere coordination at vacancy sites than the bacteriogenic MnO₂: 0.09 versus 0.14 mol Ni mol^–1 Mn. In addition, 50–100% of the adsorbed Ni partitioned to the MnO₂, which accounts for less than 20% of the sorbent on a mass basis. The vacancy content, which appears to increase with the kinetics of MnO₂ precipitation, exerts significant control on biomineral reactivity