Bioaccumulation of silver by a multispecies community of bacteria |
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Authors: | Robert C. Charley Alan T. Bull |
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Affiliation: | (1) Department of Applied Biology, University of Wales, Institute of Science and Technology, King Edward VII Avenue, CF1 3NU Cardiff, Wales, UK;(2) Present address: Department of Applied Microbiology, University of Strathclyde, G1 1XW Glasgow, Scotland, UK |
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Abstract: | A stable community of bacteria that had unusually high tolerance of soluble silver was isolated from soil by chemostat enrichment. The community consisted of three bacteria: Pseudomonas maltophilia, Staphylococcus aureus and a coryneform organism. The pseudomonas was primarly responsible for the silver resistance. The tolerance of high silver concentrations, up to 100 mM Ag+, was greatly reduced when the community was grown in the absence of silver. Pseudomonas maltophilia comprised approximately 50% by numbers of the community when grown in chemostats in the presence or absence of Ag+ but large fluctuations occurred in population sizes of the other two bacteria; the S. aureus population was small (less than 1%) in the presence of Ag+ but comparised a third of the total numbers when Ag+ was omitted from the medium. Silver-resistant respiration of the silveradapted community was significant even when it was confronted with high concentrations of Ag+. In contrast the respiration of the coryneform organism and particularly S. aureus was highly sensitive to silver. The inhibition constants for silver-sensitive respiration were 0.78 mM and 0.04 mM for silver acclimatized and nonacclimatized communities respectively.The community had great capacity for silver bioaccumulation. Maximum concentrations of over 300 mg silver per g dry weight of biomass were recorded at an accumulation rate of 21 mg Ag+ h-1 (g biomass)-1. The extent of silver removal from solution was a function of initial concentration of silver; at low external concentrations (ca. 1 mM) all the silver was rapidly removed from solution, at high concentrations (ca. 12 mM) 84% removal occurred in 15 h. |
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Keywords: | Silver Bioaccumulation Bacterial community Pseudomonas maltophilia Chemostat enrichment isolation |
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