08/01/2003
New Technique for Identification of Bacterial Spores Featured on Cover of Applied Spectroscopy
Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) has been applied for the first time to the identification and speciation of bacterial spores.
The Science
Research at the Pacific Northwest National Laboratory (PNNL) has led to a new technique for identifying strains of bacterial spores that requires a minimum of preparation of test samples and gives highly accurate results. An article on the project is featured on the cover of the August 2003 issue of the widely read journal Applied Spectroscopy. The technique is based on the combination of Fourier Transform Infrared (FTIR) spectroscopy and Photoacoustic spectroscopy (PAS). FTIR offers good differentiation among highly similar substances, while PAS enables the technique to be used on solid samples without the need for extensive pretreatment. The research group developed new algorithms for classification of samples based on the FTIR-PAS experimental results. With this spectroscopic/statistical approach it was proved possible to differentiate bacterial from non-bacterial materials, determine which bacterial samples corresponded to ones in the FTIR-PAS reference library in the laboratory, and to identify the exact strain of those bacterial spores. An accuracy of better than 90% was obtained at each stage. Further research is planned to expand the range of bacteria in the library, to determine the effect of varying growing conditions, and to test the applicability of the technique to mixtures of spores. The instrumentation has the potential to be made portable for testing of samples in the field.
Summary
A total of forty specimens representing five strains of Bacillus spores were analyzed. Spores were deposited, with minimal preparation, into the photoacoustic sample cup and their spectra recorded. Principal component analysis (PCA), classification and regression trees (CART), and Mahalanobis distance calculations were used on this spectral library to develop algorithms for step-wise classification at three levels: (1) bacterial/nonbacterial, (2) membership within the spore library, and (3) bacterial strain.
BER Program Manager
Amy Swain
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]
Funding
The project was carried out at the William R. Wiley Environmental Molecular Sciences Laboratory at PNNL and supported by Laboratory Directed Research and Development funds.
References
Thompson, S. E., N. S. Foster, T. J. Johnson, N. B. Valentine, and J. E. Amonette. 2003. “Identification of Bacterial Spores Using Statistical Analysis of Fourier Transform Infrared Photoacoustic Spectroscopy Data,” Applied Spectroscopy 57(8). DOI:10.1366/000370203322258832.