A microbiological assay based on ampicillin-induced lysis of Escherichia coli auxotrophs

Abstract

A novel quantitative microbiological assay is presented. This is based on the finding that the rate of ampicillin-induced lysis of cultures of an auxotrophic E. coli mutant depends on the concentration of the required growth factor the mutant is defective for.

Contrary to the usual methods the new procedure is less time consuming and needs no more than 60 to 90 minutes, there is no requirement for sterile conditions. It was possible to estimate amounts of about 0.5 μg/ml in raw extracts of biological material.