β-GLUCOSIDASE SYSTEM OF NEUROSPORA CRASSA I. β-

Abstract

Eberhart, Bruce (University of North Carolina, Greensboro), David F. Cross, and Lewis R. Chase . β-Glucosidase system of Neuspora crassa . I. β-Glucosidase and cellulose activities of mutant and wild-type strains. J. Bacteriol. 87: 761–770. 1964.—A mutant strain, gluc-1 , of Neurospora crassa was isolated and characterized by its low level of β-glucosidase activity. The mutant was selected by testing irradiated colonies for extracellular β-glucosidase activity. Strains containing the gluc-1 gene were also visibly detected by their reduced ability to destroy esculin in their growth media. The mutant strain grew at wild-type rates with cellobiose or carboxymethylcellulose as carbon sources. This auxotrophic similarity with wild type is explained by the presence of at least two β-glucosidases (and possibly two cellulases) in Neurospora that act complementarily. The thermolabile β-glucosidase was destroyed after 1 min of incubation at 60 C. This enzyme was present in mycelia but absent in conidial extracts. A second β-glucosidase that is comparatively stable at 60 C was present in both mycelia and conidia. A partial separation of these enzymes was achieved with ammonium fractionation of mycelial extracts of gluc-1 and wild-type strains. Thermolabile β-glucosidase and cellulase activity appear not to be affected by the gluc-1 mutation, whereas the thermostable glucosidase is greatly reduced in gluc-1 strains.