Microbes play key geoactive roles in the biosphere, particularly in the areas of element biotransformations and biogeochemical cycling, metal and mineral transformations, decomposition, bioweathering, and soil and sediment formation. All kinds of microbes, including prokaryotes and eukaryotes and their symbiotic associations with each other and 'higher organisms', can contribute actively to geological phenomena, and central to many such geomicrobial processes are transformations of metals and minerals. Microbes have a variety of properties that can effect changes in metal speciation, toxicity and mobility, as well as mineral formation or mineral dissolution or deterioration. Such mechanisms are important components of natural biogeochemical cycles for metals as well as associated elements in biomass, soil, rocks and minerals, e.g. sulfur and phosphorus, and metalloids, actinides and metal radionuclides. Apart from being important in natural biosphere processes, metal and mineral transformations can have beneficial or detrimental consequences in a human context. Bioremediation is the application of biological systems to the clean-up of organic and inorganic pollution, with bacteria and fungi being the most important organisms for reclamation, immobilization or detoxification of metallic and radionuclide pollutants. Some biominerals or metallic elements deposited by microbes have catalytic and other properties in nanoparticle, crystalline or colloidal forms, and these are relevant to the development of novel biomaterials for technological and antimicrobial purposes. On the negative side, metal and mineral transformations by microbes may result in spoilage and destruction of natural and synthetic materials, rock and mineral-based building materials (e.g. concrete), acid mine drainage and associated metal pollution, biocorrosion of metals, alloys and related substances, and adverse effects on radionuclide speciation, mobility and containment, all with immense social and economic consequences. The ubiquity and importance of microbes in biosphere processes make geomicrobiology one of the most important concepts within microbiology, and one requiring an interdisciplinary approach to define environmental and applied significance and underpin exploitation in biotechnology.

http://dzumenvis.nic.in/Physiology/pdf/Metals,%20minerals%20and%20microbes.pdf

Metals, minerals and microbes: geomicrobiology and bioremediation

http://www.bashanfoundation.org/gmaweb/pdfs/P-removal.pdf

Recent advances in removing phosphorus from wastewater and its future use as fertilizer (1997-2003).

Bacillus sphaericus JG-A12 is a natural isolate recovered from a uranium mining waste pile near the town of Johanngeorgenstadt in Saxony, Germany. The cells of this strain are enveloped by a highly ordered crystalline proteinaceous surface layer (S-layer) possessing an ability to bind uranium and other heavy metals. Purified and recrystallized S-layer proteins were shown to be phosphorylated by phosphoprotein-specific staining, inductive coupled plasma mass spectrometry analysis, and a colorimetric method. We used extended X-ray absorption fine-structure (EXAFS) spectroscopy to determine the structural parameters of the uranium complexes formed by purified and recrystallized S-layer sheets of B. sphaericus JG-A12. In addition, we investigated the complexation of uranium by the vegetative bacterial cells. The EXAFS analysis demonstrated that in all samples studied, the U(VI) is coordinated to carboxyl groups in a bidentate fashion with an average distance between the U atom and the C atom of 2.88 ± 0.02 A and to phosphate groups in a monodentate fashion with an average distance between the U atom and the P atom of 3.62 ± 0.02 A. Transmission electron microscopy showed that the uranium accumulated by the cells of this strain is located in dense deposits at the cell surface.

Complexation of Uranium by Cells and S-Layer Sheets of Bacillus sphaericus JG-A12

Developments in Bioremediation of Soils and Sediments Polluted with metals and Radionuclides - 1. Microbial Processes and Mechanisms Affecting Bioremediation of Metal Contamination and Influencing metal Toxicity and Transport

http://www.joelkostka.net/pubs/AkobFEMS07.pdf

Metabolically active microbial communities in uranium‐contaminated subsurface sediments

A strain of polyphosphate-synthesizing, phosphate-releasing Acinetobacter johnsonii was isolated from a wastewater treatment plant operating enhanced biological phosphate removal (EBPR) and was used to remove La(3+) from solution via precipitation of cell-bound LaPO(4). The effect of repeated aerobic-anaerobic cycles on the carbon and phosphate metabolism of the organism was studied in attempts to promote increased phosphate flux using a three-stage, continuous bioreactor comprising aerobic, anaerobic and settling vessels. The bioreactor was operated in two modes: In flow-through mode, cells were grown aerobically with acetate as the sole carbon source, promoting excess phosphate uptake (up to 5.0 mmol/l=3.0 mmol/g protein). Cells were diluted into the anaerobic vessel where phosphate was released (up to 1.0 mmol/l=0.3 mmol/g protein), and thence to waste. The system was initially operated to steady state in flow-through mode, then switched to recycle mode. Here the anaerobic vessel output passed to a settling vessel from which settled cells were returned to the aerobic vessel. Carbon source (acetate) was supplied only to the anaerobic vessel; increased anaerobic acetate uptake was observed during recycle, which was sustained when the system was returned to flow-through mode and was related to increased cellular lipid inclusions by flow cytometry and electron microscopy. These phenomena may represent adaptation of cells to aerobic-anaerobic cycling with aerobic carbon/energy limitation. Addition of La(3+) to the anaerobic vessel during recycle mode promoted removal of 95% of the La(3+) from a 0.1 to 0.3 mM (14-42 ppm) solution at the expense of biogenic phosphate.

H Eccles

Papers

Phosphate uptake and release by Acinetobacter johnsonii in continuous culture and coupling of phosphate release to heavy metal accumulation.