One colony possessed a particularly small ring of hydrolysis around the germinated zoospore. At least 24,000 colonies obtained after exposure to MNNG were scored for cellulase. Several colonies were found to possess unusually small rings of hydrolysis. Isolation of derepressed cellulase mutants was not possible in experiments using cellulose overlays containing glucose. All putative cellulase mutant colonies failed to grow upon subsequent transfer we believe because exposure to O2 was considered excessive during the overlay procedure.
Efforts are presently underway to reduce such exposure.
We conclude that the anaerobic fungus Neocallimastix frontalis EB188 is susceptible to UVL, MNNG and EMS killing in a dose-dependent manner. This fungus is also capable of photoreactivation of UVL caused damage. This is surprising since this organism is rarely in the presence of sunlight. DNA repair capabilities this fungus possesses. Such mutants will be very helpful in our studies to elucidate the details of gene control with respect to cellulase within these fungi.