Barbara L. Illman

3D spectral imaging with synchrotron Fourier transform infrared spectro-microtomography

We report Fourier transform infrared spectro-microtomography, a nondestructive three-dimensional imaging approach that reveals the distribution of distinctive chemical compositions throughout an intact biological or materials sample. The method combines mid-infrared absorption contrast with computed tomographic data acquisition and reconstruction to enhance chemical and morphological localization by determining a complete infrared spectrum for every voxel (millions of spectra determined per sample).

Oxygen Free Radical Detection in Wood Colonized by the Brown-Rot Fungus, Postia Placenta

Rapid depolymerization of cellulose occurs shortly after brown-rot fungi colonize wood. The chemical agent responsible for this initial depolymerization is most likely a low molecular weight compound (Cowling, 1961; Cowling and Brown, 1969) that diffuses through the crystalline microfibrils of cellulose, degrading the amorphous non-crystalline regions (Cowling and Brown, 1969; Highley, Palmer, Murmanis, 1983). It is important to identify the depolymerizing agent(s) produced by brown-rot fungi, because such information could serve as a foundation for the development of new methods to prevent wood decay.

Decomposition of Wood by Brown-Rot Fungi

Many different types of organisms deteriorate wood, but the greatest damage is microbial decay caused by fungi (Figures 1 and 2). Fungal decay is by far the most serious type of damage to wood in use, because it can cause structural failure that, at times, is very rapid. It is virtually impossible to accurately assess the monetary loss caused by decay that destroys wood products or impairs their aesthetic qualities because records are rarely kept. Treatments are available that can either prevent or retard the destructive action of decay. Nevertheless, it is estimated that annual losses of over

High-resolution microtomography for density and spatial information about wood structures

1 billion in the United States result from fungal deterioration of untreated or inadequately treated wood.

Manganese as a Probe of Fungal Degradation of Wood

Microtomography has successfully been used to characterize loss of structural integrity of wood. Tomographic images were generated with the newly developed third generation x-ray computed microtomography (XCMT) instrument at the X27A beamline at the national Synchrotron Light source (NSLS). The beamline is equipped with high-flux x-ray monochromator based on multilayer optics developed for this application. The sample is mounted on a translation stage with which to center the sample rotation, a rotation stage to perform the rotation during data collection and a motorized goniometer head for small alignment motions. The absorption image is recorded by a single-crystal scintillator, an optical microscope and a cooled CCD array detector. Data reconstruction has provided three-dimensional geometry of the heterogeneous wood matrix in microtomographic images. Wood is a heterogeneous material composed of long lignocellulose vessels. Although wood is a strong natural product, fungi have evolved chemical systems that weaken the strength properties of wood by degrading structural vessels. Tomographic images with a resolution of three microns were obtained nonintrusively to characterize the compromised structural integrity of wood. Computational tools developed by Lindquist et al (1996) applied to characterize the microstructure of the tomographic volumes.

Synchrotron tomography of a boreal forest bark beetle

Transition state metals, such as manganese (Mn) and iron (Fe), have been reported to be involved in fungal degradation of wood (Ellis, 1959; Shortle and Shigo, 1973; Blanchette, 1984; Glenn et al., 1986). Manganese is also involved in the enzymatic degradation of lignin model compounds by the white-rot fungus Phanaerochaete chrysosporium Burds. (Tien and Kirk, 1984; Glenn et al., 1986). Iron is believed to be involved in the oxidative degradation of cellulose by brown-rot fungi (Cowling and Brown, 1969; Koenigs, 1974; Schmidt et al., 1981).

Quantifying sources of variation in the frequency of fungi associated with spruce beetles: Implications for hypothesis testing and sampling methodology in bark beetle-symbiont relationships

The tomography beamline X27A at the National Synchrotron Light Source at Brookhaven National Laboratory was used to study the destructive spruce bark beetle, Dendroctonus rufipennis (Kirby). The x-ray computed microtomography (CMT) instrument is equipped with filtered white x-ray beam with energy of around 18 keV and, alternatively, a monochromatic beam with energy of around 4 to 14 keV and a 1% band pass. The instrument records microtomographic volumes with 108 to 109 voxels and spatial resolution down to about 3- micron voxels. Three-dimensional image reconstruction provides density and spatial information about solid heterogeneous forms. We have demonstrated that CMT images can be used to nondestructively characterize the internal structure of the beetle - symbiont fungal complex as part of an effort to understand the role of these organisms in the devastation of spruce forests throughout south-central Alaska.