A GENETIC STUDY OF ELECTROPHORETICALLY VARIANT EXTRACELLULAR AMYLOLYTIC ENZYMES OF WILD-TYPE STRAINS OF ASPERGILLUS NIDULANS

Ninety strains assigned to Aspergillus nidulans produced extracellular amylolytic enzymes in a defined medium containing soluble starch as the organic carbon source. Acrylamide gel electrophoresis of freeze-dried culture filtrates gave 6-9 sites of amylolytic activity accommodated by nine patterns. Eighty-one strains exhibited pattern 1 or 2 and not more than two displayed one of the remaining seven patterns. Crosses between strains with different patterns succeeded only for strains with pattern 1 or 2. Esterase and phosphatase zymograms for mycelial extracts indicated that strains with amylase pattern 1 or 2 are A. nidulans, while the strains with the other amylase patterns are probably cryptic or sibling species. Two codominant alleles are responsible for the different electrophoretic mobility of one pair of amylolytic sites in zone 2 which distinguishes patterns 1 and 2. The pair of sites may be determined by duplicate loci.