title: Toxicity effects on metal sequestration by microbially-induced carbonate precipitation.
abstract: Biological precipitation of metallic contaminants has been explored as a remedial technology for contaminated groundwater systems. However, metal toxicity and availability limit the activity and remedial potential of bacteria. We report the ability of a bacterium, Sporosarcina pasteurii, to remove metals in aerobic aqueous systems through carbonate formation. Its ability to survive and grow in increasingly concentrated aqueous solutions of zinc, cadmium, lead and copper is explored, with and without a metal precipitation mechanism. In the presence of metal ions alone, bacterial growth was inhibited at a range of concentrations depending on the metal. Microbial activity in a urea-amended medium caused carbonate ion generation and pH elevation, providing conditions suitable for calcium carbonate bioprecipitation, and consequent removal of metal ions. Elevation of pH and calcium precipitation are shown to be strongly linked to removal of zinc and cadmium, but only partially linked to removal of lead and copper. The dependence of these effects on interactions between the respective metal and precipitated calcium carbonate are discussed. Finally, it is shown that the bacterium operates at higher metal concentrations in the presence of the urea-amended medium, suggesting that the metal removal mechanism offers a defence against metal toxicity.
authors.affiliation: Cardiff School of Engineering, Cardiff University, Queen's Buildings, The Parade, Cardiff CF24 3AA, United Kingdom; College of Engineering, Al-Muthanna University, Samawah, Iraq.
authors.forename: Ahmed J
authors.initials: AJ
authors.lastname: Mugwar
authors.affiliation: Cardiff School of Engineering, Cardiff University, Queen's Buildings, The Parade, Cardiff CF24 3AA, United Kingdom. Electronic address: harbottlem@cardiff.ac.uk.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Harbottle
mesh_terms: D001673:Biodegradation, Environmental; D002119:Calcium Carbonate / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry*; D011232:Chemical Precipitation; D019216:Metals, Heavy / Q000737:chemistry*; D058644:Sporosarcina / Q000378:metabolism*
chemical_list: D002254:Carbonates; D019216:Metals, Heavy; D002119:Calcium Carbonate
keywords: Bioprecipitation; Bioremediation; Heavy metals; Sporosarcina pasteurii; Urea hydrolysis