Assessment of the metabolic activity of Acremonium chrysogenum using Acridine Orange

A method is described for the assessment of the metabolic activity of the f ilamentous fungus Acremonium chrysogenum using the fluorescent dye Acridine Orange. Changes in metabolic activity are indicated by a reversible red-gr een shift in the colour of the dye, quantifiable by image analysis. A. chry sogenum mycelia exhibited an overwhelmingly green colour in circumstances l eading to high substrate uptake, while under carbon starvation they appeare d orange-red. It is believed these colour changes reflected changes in inte rnal pH. The method provides a visual tool for the investigation of the met abolic behaviour of filamentous fungi.