This Article Full Text Full Text (PDF) An erratum has been published Other Versions of this Article: AEM.02783-07v1 74/15/4934    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Google Scholar Articles by Phoenix, V. R. Articles by Holmes, W. M. PubMed PubMed Citation Articles by Phoenix, V. R. Articles by Holmes, W. M. Agricola Articles by Phoenix, V. R. Articles by Holmes, W. M.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, August 2008, p. 4934-4943, Vol. 74, No. 15
0099-2240/08/$08.00+0     doi:10.1128/AEM.02783-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Magnetic Resonance Imaging of Structure, Diffusivity, and Copper Immobilization in a Phototrophic Biofilm

Department of Geographical and Earth Sciences, Gregory Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom,¹ 7T MR Facility, Wellcome Surgical Institute, University of Glasgow, Glasgow G61 1QH, United Kingdom²

Received 10 December 2007/ Accepted 5 June 2008

Magnetic resonance imaging (MRI) was used to spatially resolve the structure, water diffusion, and copper transport of a phototrophic biofilm and its fate. MRI was able to resolve considerable structural heterogeneity, ranging from classical laminations 500 µm thick to structures with no apparent ordering. Pulsed-field gradient (PFG) analysis spatially resolved water diffusion coefficients which exhibited relatively little or no attenuation (diffusion coefficients ranged from 1.7 x 10^–9 m² s^–1 to 2.2 x 10^–9 m² s^–1). The biofilm was then reacted with a 10-mg liter^–1 Cu²⁺ solution, and transverse-parameter maps were used to spatially and temporally map copper immobilization within the biofilm. Significantly, a calibration protocol similar to that used in biomedical research successfully quantified copper concentrations throughout the biofilm. Variations in Cu concentrations were controlled by the biofilm structure. Copper immobilization was most rapid (5 mg Cu liter^–1 h^–1) over the first 20 to 30 h and then much slower for the remaining 60 h of the experiment. The transport of metal within the biofilm is controlled by both diffusion and immobilization. This was explored using a Bartlett and Gardner model which examined both diffusion and adsorption through a hypothetical film exhibiting properties similar to those of the phototrophic biofilm. Higher adsorption constants (K) resulted in longer lag times until the onset of immobilization at depth but higher actual adsorption rates. MRI and reaction transport models are versatile tools which can significantly improve our understanding of heavy metal immobilization in naturally occurring biofilms.

Published ahead of print on 13 June 2008.