A kinetic method for estimating the biomass of microbial functional groups in soil

A kinetic method is presented for estimating the biomass and characterizing the in situ physiological state of microorganisms capable of carping out specific metabolic function. Fresh soil samples are incubated with a particular substrate under specified controlled conditions, the rates of substrate uptake or product formation being continuously recorded. The observed dynamic curve is approximated by a mathematical model which simulates substrate-induced microbial growth, microbial biomass at zero time being identified as one of the model's parameters. Examples of the developed technique are presented for the following groups of soil microorganisms: aerobic heterotrophic (including prokaryotic and eukaryotic) microorganisms, chemolythotrophic bacteria (hydrogen, carboxidobacteria, nitrifying bacteria), anaerobic bacteria (methanogenic, acetogenic, sulfate- reducing, denitrifying), phototrophic microorganisms, pesticide degraders, and microbial grazers.