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Free keywords:
IDENTIFICATION SYSTEMS; BIOLOG; MARINE BACTERIA; SUBSTRATE UTILIZATION
Abstract:
Recently, the new BIOLOG identification system has offered a standardized, rapid method for determining bacterial oxidation of 95 different carbon sources simultaneously. In contrast to other systems based on color changes of pH indicators, the BIOLOG technique relies on the irreversible reduction of a tetrazolium redox-dye to the purple formazan as an indicator for organic substrate oxidations. For identification purposes, the metabolic profiles obtained are compared with data bases containing characteristic profiles of 569 Gram-negative and 225 Gram-positive bacteria, but only a few bacteria of ecological interest are included. To prove, whether results from the BIOLOG system can be used for rapid identification of bacteria not included in the data bases, 80 marine strains already characterized by means of their substrate utilizations were additionally examined in BIOLOG GN MicroPlates. In these different test methods, 1 to 13% of the strains gave deviating results with miscellaneous carbohydrates, 14 to 30% with organic acids and 11 to 66% with amino acids, indicating that BIOLOG results can lead to incorrect identification of strains, because descriptions of bacteria in the literature are based on utilization of organic substrates as sole carbon and energy sources. The new technique may be used if already identified reference strains are included. The most valuable advantage of the BIOLOG technique in ecological research is the rapid differentiation of large numbers of isolates by means of their metabolic profiles. However, strains cluster differently, when substrate utilization or the BIOLOG system are used for their characterization.
