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Summary The color development curves obtained from multiple readings of Biolog GN microtiter plates over a long incubation time were fitted to the Gompertz function. This yielded — for each sole-carbon source — the incubation time independent and biologically relevant Gompertz parameters A (maximal extent of color development), μ M (specific color development rate) and λ (lagtime). To evaluate the applicability of the model, the coefficients of determination, the residuals, the biological significance of the parameters, the stability of the parameter estimates and the predicting power of the model were determined. For the pure strains Vibrio alginolyticus and Pseudomonas fluorescens the model passed all the criteria. For the model community consisting of a mixture of 9 strains, all criteria were met for almost all the oxidized carbon sources. However, a high amount of measuring points in the color development curve is necessary (preferably >20) and the reading frequency needs to be the highest in the lagphase and the exponential phase to ensure a high stability and predictability of the estimates of μ M and λ, especially when the color develops very rapidly in the wells. For a few carbon sources the Gompertz model was not appropriate, as the color development curve showed clearly 2 tiers. However, it is substantiated that the second tier may be eliminated from the time series, which allowed the model again to pass all the criteria. Finally, comparison of Biolog fingerprints of environmental samples was made with principal component analysis of the estimated Gompertz parameters for each carbon source. It is shown that this approach is practicable and may yield consistent results for environmental microbial community analysis. |
