Microtechnique for Most-Probable-Number Analysis

Abstract
A microtechnique based on the most-probable-number (MPN) method was developed for the enumeration of the ammonium-oxidizing population in soil samples. An MPN table for a research design ([8 by 12], i.e., 12 dilutions, 8 replicates/dilution) is presented. A correlation of 0.68 was found between MPN determined by the microtechnique and the standard tube technique. Higher MPN were obtained with the microtechnique with increased accuracy in endpoint determinations being a possible cause. Considerable savings of time, space, equipment and reagents are observed using this method. The microtechnique described may be adapted to other microbial populations using various types of media and endpoint determinations.