Calcafluor screen for chitin biosynthesis inhibitors

Abstract

A method for the identification of agents which inhibit chitin synthesis, thus exhibiting potential fungicidal and insecticidal activity, involves the incubation of test samples in neutral cultures containing calcofluor white, a fluorochrome that causes lethal chitin hyper-polymerization in the yeast. Cultures containing samples that inhibit chitin synthesis exhibit enhanced growth because the growing fungus is rescued from the adverse effects of calcofluor white. In the practice of the invention, the test sample is added to a culture or culture area containing calcofluor white and the culture is incubated with the test sample for such time under such conditions sufficient to observe yeast cell growth inhibition in a corresponding culture or culture area containing calcofluor but no test sample. The extent of growth in the culture or culture area containing test sample is then compared with the extent of growth in the culture or culture area containing no test sample, and the presence of chitin synthesis inhibition is determined by observation of whether culture growth in the presence of test sample exceeds growth in its absence. Preferred embodiments employ test samples on disks or in wells in solidified cultures and a known chitin synthesis inhibitor as a positive control which is compared to the test sample.