XVI International Botanical Congess

The cyanobacterium Scytonema ocellatum produces an antifungal, cytotoxic polyketide (tolytoxin) which can be elicited by oligomeric chitin and other fungal cell wall constituents. To characterize the mechanism of elicitor perception, we have developed a binding assay utilizing crude cyanobacterial membranes and a tritiated chitin hexamer probe. We have found a correlation between the type and chain length of oligosaccharides that can effectively compete with the chitin hexamer for binding to cell membranes and those which will induce cytotoxin biosynthesis in S. ocellatum culture. Oligosaccharides which are structurally similar to chitin, but that do not elicit tolytoxin synthesis, are found to be poor competitors of the chitin probe in our binding assay.