Spindle pole body screen for fungicides

Abstract

A method for the identification of agents which inhibit spindle pole body formation or function, thus exhibiting selective fungicidal activity, involves the incubation of test samples in cultures of a Saccharomyces cerevisiae strain that produces excess numbers of spindle pole bodies. Cultures containing samples that inhibit spindle pole bodies exhibit enhanced growth because the growing yeast is rescued from the adverse effects of excess spindle bodies. In the preferred practice of the invention, the test sample is added to a S. cerevisiae culture or culture area containing a strain that has a conditional mutation producing excess spindle pole bodies, such as diploid esp1-1 strains. The culture or culture area is preincubated under permissive conditions wherein the strain can grow to some extent, and then conditions are shifted to restrictive conditions so that the mutant strain either cannot grow or grows poorly. The extent of growth in the culture or culture area containing test sample is then compared with the extent of growth in the absence of test sample, and the presence of spindle pole body 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, facilitating easy visual inspection of growth. A presumptive spindle pole body inhibitor, identified in random screening, is used as a positive control which can be compared to the test sample.