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Submitted to: Journal of Microbiological Methods
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/20/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Many problems in microbiology require that bacteria be identified. For example, bacteria that suppress plant disease need to be thoroughly characterized before they can be released into the environment. Bacteria have to be identified in the clinical laboratory in order to treat disease. One of the most powerful and widely used methods for identification of bacteria is by analysis of the fatty acids that are present in the lipids of bacterial membranes. The Microbial Identification System (Microbial ID, Inc., Newark, DE) is the only commercially available system for this purpose. While it works very well, it is not very sensitive, and large quantities of bacteria are required. We developed a very simple modification to the system that increases the sensitivity enormously, while still allowing the preexisting databases of fatty acids and bacteria to be used. This procedure allows microbiologists to identify bacteria from individual single colonies, whereas with the conventional procedure bacteria must be removed from a large portion of a petri dish. This may be useful for rapid screening of large numbers of bacteria, slowly growing bacteria, and bacteria that do not grow to high culture density. Technical Abstract: While a commercially available system for microbial identification by fatty acid analysis (Microbial Identification System, MIDI Inc., Newark, Delaware, USA) is available, it requires approximately 40 mg wet weight of biomass. Various authors have published methods for fatty acid analysis of single colonies, but no database of organisms has been developed for those methods. A modification of the MIDI system to increase sensitivity while maintaining relative retention times and peak areas allows the standard peak naming tables, and libraries of organisms to be used with single colonies. Samples are evaporated down before injection to concentrate the fatty acids, while splitless injection is used to allow more samples to enter the gas chromatograph. Several known bacteria were correctly identified by this method. |
