Optimization of conditions for culture of test bacteria used for direct bioautographic TLC detection. 2. Gram-negative test bacterium:Escherichia coli

Abstract

Direct bioautography is a potent means of obtaining information about the antimicrobial activity of a compound separated from a complex mixture. In this process the developed TLC plate is dipped into a broth culture of a test bacterium and the bacterium will grow directly on the plate. Optimum experimental conditions must, however, be used for each test bacterium.The main purpose of this study was to find optimum culture conditions for a Gram-negative test bacterium, Escherichia coli (ATCC 25922) enabling us to establish a direct bioautographic method with the shortest possible performance time. Because the intracellular adenosine-5′-triphosphate (ATP) level is a direct and sensitive measure of bacterial well-being, ATP assay was used for this purpose. As far as we know this is the first report of the use of an ATP method for optimization of direct bioautography with E. coli . Our optimizing experiments on E. coli culture showed that the bacteria had to be in the log phase (optical density, OD 600nm = 0.1...