BACTERIAL ASSAY FOR QUANTITATIVE MEASUREMENT OF NANOMOLAR CONCENTRATIONS OF A METABOLITE

A mutant of Pseudomonas fluorescens was used to develop a radioligand, competitive binding assay to quantitatively measure gamma-aminobutyri c acid. The highly reliable and reproducible assay was sensitive (nM d etection), rapid, and easy to perform. Nonspecific activity and scatte r were insignificant. Radiolabel was irreversibly fixed by the cells i n an energy-dependent reaction. The finding that a bacterium was effec tive in quantitatively detecting nanomolar amounts of a metabolite sug gests that other bacteria or their mutants might be used in competitiv e binding assays to detect and quantify amino acids or other substance s occurring in trace amounts. (C) 1995 Academic Press, Inc.