The contribution of individual populations to the Biolog pattern of model microbial communities

Model microbial communities consisting of 2 or 3 bacterial strains were used to validate the Biolog system as a tool for microbial community analysis. The a priori known taxonomical structure and carbon substrate utilization pattern of the separate community members allowed the detection and analysis of the contribution of the individual populations to the whole-community patterns. All the whole-community Biolog patterns were dominated by the fastest growing strain, even when this strain represented only 10% of the total inoculated cell numbers, and there was evidence that the activity of the slowest growing member of the model community was partially masked by the other ones. However, differentiation of these closely related microbial communities was still possible with principal component analysis, provided that the incubation time was well chosen. The problem of choosing the right incubation time was overcome by the use of the parameters of the Gompertz equation, which was fitted to the color development in each Biolog well. These kinetic parameters were independent of the incubation time and still allowed a clear separation of the closely related model communities by means of principal component analysis. This approach is proposed as an alternative way for processing Biolog data in microbial community analysis.