Dissimilar response of microbial communities in Biolog GN and GN2 plates

Changes to the design of Biolog GN microplates, a reliable tool for the characterization of microbial communities, have recently been implemented. The omission of two chemicals in newer Biolog plates resulted in lower total carbon source utilization as measured by average well color development (AWCD) and the number of responsive wells for a variety of microbial communities, including soil, groundwater, and laboratory microcosms. Evaluation of the kinetic profiles (i.e. fit to Gompertz equation) revealed that the average responsive well in the GN2 plates displayed a longer lag phase (λ) and a reduced maximum extent (A), but equivalent maximum rate (μmax) of color development compared to GN plates. Further, non-responsive wells in the GN2 plates were weakly responsive (in terms of all kinetic parameters) in the GN plates. The influence these altered responses will have on classification of samples, as well as possible long-term solutions to media formulations for community-level physiological profiling (CLPP), are discussed.