MICROBIAL COMMUNITY ANALYSIS - A KINETIC APPROACH TO CONSTRUCTING POTENTIAL C-SOURCE UTILIZATION PATTERNS

The analysis of multiple substrate metabolism by assemblages of bacter ial strains may be used to differentiate inocula from environmental sa mples. Biolog plates, 96-well microtiter plates containing nutrients, a single carbon test substrate in each well and a tetrazolium redox dy e to monitor substrate oxidation, have been used for this purpose. One of the difficulties faced by users of this technique is determining w hich substrates have been metabolized. Reliance on single-time-point a bsorbance data for each well is problematic due to variably non-linear rates of color development for each well. Previous efforts to use col or-normalized single plate readings have been successful in discrimina ting between environmental sample types, but substrate-use contributio ns to sample classifications vary depending on the duration of the pla te incubation. We present a model based on the logistic equation for d ensity-dependent population growth providing a good (low chi(2)) fit t o the sigmoidal kinetics of color development data. The kinetic parame ters generated by the model can be used as surrogates for single-time- point data in constructing carbon source utilization patterns, and con tribution of substrate use to sample classification does not depend on incubation time. This technique obviates the need to choose the time following inoculation to read the plate absorbance data and also provi des two kinetic parameters that are invariant with respect to inoculum density. We provide a comparison of community potential substrate use analyses using single-time-point microplate-data and parameters from our kinetic model. (C) 1997 Published by Elsevier Science Ltd. Ail rig hts reserved.