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Dissolution of carbonate minerals has significant environmental effects. Microorganisms affect carbonate dissolution rates by producing extracellular metabolites, including complex polysaccharides such as alginic acid. Using a combined atomic force microscopy (AFM)/flowthrough reactor apparatus, we investigated the effects of alginic acid on calcite(More)
The chrome azurol S (CAS) assay measures the chelating activity of siderophores, but its application (especially to fungi) is limited by toxicity issues. In this note, we describe a modified version of the CAS assay that is suitable for quantifying siderophore exudation for microorganisms, including fungi.
Siderophores, biogenic chelating agents that facilitate the solubilization and uptake of ferric iron, form stable complexes with a wide range of nutrient and contaminant metals and thus may profoundly affect their fate, transport, and biogeochemical cycling. To understand more comprehensively the factors that control the stability and reactivity, as well as(More)
Denitrification is a critical biogeochemical process that results in the conversion of nitrate to volatile products, and thus is a major route of nitrogen loss from terrestrial environments. Riparian buffers are an important management tool that is widely utilized to protect water from non-point source pollution. However, riparian buffers vary in their(More)
Siderophores, biogenic chelating agents that facilitate Fe(III) uptake through the formation of strong complexes, also form strong complexes with Mn(III) and exhibit high reactivity with Mn (hydr)oxides, suggesting a pathway by which Mn may disrupt Fe uptake. In this review, we evaluate the major biogeochemical mechanisms by which Fe and Mn may interact(More)
Ethylenediamine tetraacetate (EDTA)-mediated calcite dissolution occurs via a different process than water-promoted dissolution. Near-atomic-scale observations in EDTA solutions demonstrate that, after penetration through a critical pit depth barrier, step velocity increases linearly with pit depth for EDTA-promoted dissolution. The parallel processes of(More)
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(More)
Although siderophores are generally viewed as biological iron uptake agents, recent evidence has shown that they may play significant roles in the biogeochemical cycling and biological uptake of other metals. One such siderophore that is produced by A. vinelandii is the triscatecholate protochelin. In this study, we probe the solution chemistry of(More)
Recent studies suggest that aqueous Mn(ll) complexes, particularly those with non-carboxylated ligands such as microbial siderophores, may be stable in soil and aquatic environments. In this paper, we determine the stability constants for Mn(ll) and Mn(lll) complexes with the common trihydroxamate siderophore, desferrioxamine B (DFOB). Base and redox(More)
Mineral inclusions, present in aqueous atmospheric salt droplets, regulate crystallization when relative humidity decreases by providing a surface for heterogeneous nucleation and thus reducing the critical supersaturation. Although laboratory studies have quantified these processes to some extent, the diverse atmospheric mineralogy presents more chemical(More)