Quantitative mapping of metal species in bacterial biofilms using scanning transmission X-ray microscopy

J.J. Dynes(1), T. Tyliszczak(2), T. Araki(1), J.R. Lawrence(3), G. D.W. Swerhone(3), G.G. Leppard(4) and A.P. Hitchcock(1)*

1. Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada L8S 4M1,
2. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720,
3. National Water Research Institute, 11 Innovation Boulevard, Saskatoon, Saskatchewan, Canada S7N 3H5
4. National Water Research Institute, P.O. Box 5050, Burlington, Ontario, Canada L7R 4A6

Abstract:

A scanning transmission X-ray microscope illuminated with synchrotron light was used to investigate the speciation and spatial distributions of metals in a microbial biofilm cultivated from river water. Metal 2p absorption edge signals were used to provide metal speciation (through shapes of the absorption spectra) and quantitative spatial distributions of the metal species. This paper presents sample data and describes methods for extracting quantitative maps of metal species from image sequences recorded in the region of the metal 2p edges. Comparisons were made with biochemical characterization of the same region using images recorded at the C 1s and O 1s edges. The method is applied to detailed quantitative analysis of ferrous and ferric iron in a river biofilm, in concert with mapping Ni- (II) and Mn(II) species in the same region. The distributions of the metal species are discussed in the context of the biofilm structure. These results demonstrate that soft X-ray STXM measurements at the metal 2p absorption edges can be used to speciate metals and to provide quantitative spatial distribution maps for metal species in environmental samples with 50 nm spatial resolution.

10.1021/es051363   © 2006 American Chemical Society