Rapid identification of microorganisms by intrinsic fluorescence

Bhatta, H. and Goldys, E. M. and Learmonth, R. (2005) Rapid identification of microorganisms by intrinsic fluorescence. In: BiOS 2005: Imaging, Manipulation, and Analysis of Biomolecules and Cells: Fundamentals and Applications III, 24-27 Jan 2005, San Jose, CA. United States.


Microbial contamination has serious consequences for the industries that use fermentation processes. Common
contaminants such as faster growing lactic acid bacteria or wild yeast can rapidly outnumber inoculated culture yeast and produce undesirable end products. Our study focuses on a rapid method of identification of such contaminants based on autofluorescence spectroscopy of bacterial and yeast species. Lactic acid bacteria (Lactobacillus casei), and yeast (Saccharomyces cerevisiae) were cultured under controlled conditions and studied for variations in their autofluorescence. We observed spectral differences in the spectral range representative of tryptophan residues of proteins, with excitation at 290 nm and emission scanned in the 300 nm - 440 nm range. Excitation scans between 240 nm and 310 nm were also performed for the emission at 340 nm. Moreover, we observed clearly pronounced differences in the excitation and emission in the visible range, with 410 nm excitation.
These results demonstrate that bacterial and yeast species can be differentiated using their intrinsic fluorescence
both in UV and in the visible region. The comparative spectroscopic study of selected strains of Saccharomyces
yeast showed clear differences between strains. Spectrally-resolved laser scanning microscopy was carried out to
link the results obtained using ensembles of cells with spectral properties of individual cells. Strongly fluorescent subpopulation were observed for all yeast strains with excitation at 405 nm. The fluorescence spectra showed variations correlated with cell brightness. The presented results demonstrate that using autofluorescence, it is possible to differentiate between yeast and lactic acid bacteria and between different yeast species.

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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Paper)
Refereed: Yes
Item Status: Live Archive
Additional Information: Proceedings of SPIE, v. 5699
Faculty/School / Institute/Centre: Historic - Faculty of Sciences - Department of Biological and Physical Sciences (Up to 30 Jun 2013)
Faculty/School / Institute/Centre: Historic - Faculty of Sciences - Department of Biological and Physical Sciences (Up to 30 Jun 2013)
Date Deposited: 11 Oct 2007 00:16
Last Modified: 02 Jul 2013 22:30
Uncontrolled Keywords: autofluorescence; microorganisms; identification; yeast; bacteria
Fields of Research (2008): 10 Technology > 1003 Industrial Biotechnology > 100303 Fermentation
06 Biological Sciences > 0605 Microbiology > 060501 Bacteriology
06 Biological Sciences > 0605 Microbiology > 060599 Microbiology not elsewhere classified
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970106 Expanding Knowledge in the Biological Sciences
Identification Number or DOI: https://doi.org/10.1117/12.588851
URI: http://eprints.usq.edu.au/id/eprint/162

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