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Proceedings Paper

Investigating biofilm structure using x-ray microtomography and gratings-based phase contrast
Author(s): Erin A. Miller; Xianghui Xiao; Micah Miller; Paul Keller; Timothy A. White; Matthew Marshall
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Paper Abstract

Direct examination of natural and engineered environments has revealed that the majority of microorganisms in these systems live in structured communities termed biofilms. To gain a better understanding for how biofilms function and interact with their local environment, fundamental capabilities for enhanced visualization, compositional analysis, and functional characterization of biofilms are needed. For pore-scale and community-scale analysis (100’s of nm to 10’s of microns), a variety of surface tools are available. However, understanding biofilm structure in complex three-dimensional (3-D) environments is considerably more difficult. X-ray microtomography can reveal a biofilm’s internal structure, but obtaining sufficient contrast to image low atomic number (Z) biological material against a higher-Z substrate makes detecting biofilms difficult. Here we present results imaging Shewanella oneidensis biofilms on a Hollow-fiber Membrane Biofilm Reactor (HfMBR), using the x-ray microtomography system at sector 2-BM of the Advanced Photon Source (APS), at energies ranging from 12.9-15.4 keV and pixel sizes of 0.7 and 1.3 μm/pixel. We examine the use of osmium (Os) as a contrast agent to enhance biofilm visibility and demonstrate that staining improves imaging of hydrated biofilms. We also present results using a Talbot interferometer to provide phase and scatter contrast information in addition to absorption. Talbot interferometry allows imaging of unstained hydrated biofilms with phase contrast, while absorption contrast primarily highlights edges and scatter contrast provides little information. However, the gratings used here limit the spatial resolution to no finer than 2 μm, which hinders the ability to detect small features. Future studies at higher resolution or higher Talbot order for greater sensitivity to density variations may improve imaging.

Paper Details

Date Published: 17 October 2012
PDF: 9 pages
Proc. SPIE 8506, Developments in X-Ray Tomography VIII, 85061H (17 October 2012); doi: 10.1117/12.930105
Show Author Affiliations
Erin A. Miller, Pacific Northwest National Lab. (United States)
Xianghui Xiao, Argonne National Lab. (United States)
Micah Miller, Pacific Northwest National Lab. (United States)
Paul Keller, Pacific Northwest National Lab. (United States)
Timothy A. White, Pacific Northwest National Lab. (United States)
Matthew Marshall, Pacific Northwest National Lab. (United States)

Published in SPIE Proceedings Vol. 8506:
Developments in X-Ray Tomography VIII
Stuart R. Stock, Editor(s)

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