Microbial metal transformations

Anaerobic conditions are traditionally a major concern when dealing with microbial-induced transformations of wastewater in a collection system. The problem is primarily associated with the risk of hydrogen sulfide and odorous organic compounds. The corresponding problems appear as concrete and metal corrosion, health-related impacts and malodors. Such in-sewer process-related problems have been reported as early as over 50 years ago (Parker, 1945a, 1945b Pomeroy and Bowlus, 1946). 

The microbially mediated transformation of inorganic contaminants encompasses a broad spectrum of compounds. Here, we survey only a few contaminants that have a major impact on the subsurface, such as nitrates, phosphates, and toxic metals. In the subsurface, the microbial population distribution generally decreases with depth, and the moisture content and aerobic-anaerobic states fluctuate with time, affected by climatic conditions, depth of groundwater, and human intervention. 

The Michaelis-Menten equation is often employed in soil-water systems to describe kinetics of ion uptake by plant roots and microbial cells, as well as microbial degradation-transformation of organics (e.g., pesticides, industrial organics, nitrogen, sulfur, and natural organics) and oxidation or reduction of metals or metalloids. Derivation of the Michaelis-Menten equation(s) is demonstrated below. 

Microbial metal and mineral transformations in soil geochemistry 72... 

MICROBIAL METAL AND MINERAL TRANSFORMATIONS IN SOIL GEOCHEMISTRY... 

Unidentified Idaho Operations Office (USDOE) University of Toronto Microbial mineral transformations at the Fe(ll)/Fe(lll) redox boundary for solid Phase capture of strontium and other metal/radionuclide contaminants USDOE Environmental Management... 

Both precipitation-dissolution and sorption-desorption can be strongly influenced by microbial processes. Microbial redox transformations of constituent X may (especially for metals) significantly alter solubility, and microbial production of ligands can promote the release of X from immobile phases by dissolution and desorption and stabilize X in solution. 

Microbiologically influenced corrosion is defined by the National Association of Corrosion Engineers as any form of corrosion that is influenced by the presence and/or activities of microorganisms. Although MIC appears to many humans to be a new phenomenon, it is not new to the microbes themselves. Microbial transformation of metals in their elemental and various mineral forms has been an essential part of material cycling on earth for billions of years. Some forms of metals such as reduced iron and manganese serve as energy sources for microbes, while oxidized forms of some metals can substitute for... 

Metals have been shown to negatively affect nitrogen transformation and urea hydrolysis. For example, Antil et al.69 discovered that the microbial biomass in a soil receiving sewer water or industrial wastewater decreased with increasing concentrations of cadmium and nickel. The rate of urea hydrolysis was 1.6 times greater in an uncontaminated soil than in a soil containing 0.026 mg Ni g 1. Ammonium concentrations increased for up to 14 days in a soil containing over... 

Bioremediation is not restricted only to biodegradable organic contaminants. New techniques are currently under development for the bioremediation of metal-contaminated sites. Microbial activity can alter the oxidation state of some elements, reducing or increasing their mobility, and this transformation can be used for remediation purposes. 

Microbial Mediation of Weathering Transformation of Soil Minerals and Metal Dynamics... 

Bioavailability of Metals, Nonmetals and Xenobiotics Immobilized on Soil Components, (4) Distribution and Activity of Biomolecules in Terrestrial Systems, (5) Interactions between Soil Microbial Biomass and Organic Matter/Nutrient Transformations, and (6) Impact of Interactions among Soil Mineral Colloids, Organic Matter and Biota on Risk Assessment and Restoration of Terrestrial Ecosystems. There were 2 plenary lectures, 9 invited speakers, 36 oral presentations and 45 posters. Dr. N. Senesi from University of Bari, Italy, presented an IUPAC lecture entitled Metal-Humic... 

Robinson, A V., Garland, T.R., Schneiderman, G.S., Wildung, R.E., Drucker.H. Microbial Transformation of plutonium. Presented at Fifteenth Annual Hanford Life Sciences Symposium, Biological Implications of Metals in the Environment. September 29-October 1, 1975. Richland, Washington, U.S.A. 

A project at the University of Arizona (FEDRIP 1996) will study microbial dehalogenation of several compounds, including chloroform. A major part of the study will focus on the facultative anaerobic bacteria Shewanella putrefaciens sp., which is known to catalyze the transformation of carbon tetrachloride to chloroform and other as yet unidentified products. The organic substrates will also contain metals. It is hoped that the end-products from the biochemical treatment can be subjected to a photolytic finishing process that will completely mineralize any remaining halogenated compounds. 

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