|dc.description.abstract||Mortierella pusilla is a susceptible host and supports good
growth of the mycoparasite, Piptocephalis virginiana.
Uninucleate spores of M. pusilla were sUbjected to
N-methyl-N'-nitro-nitrosoguanidine (MNNG). To attain a high
mutation frequency , a 1o-minute exposure to 10 mg/ml MNNG was
used and lead to the survival of about 10 % of the spores. The
exposed spores then were plated on chitin or milk plates.
Approximately 30,000 colonies were examined after mutagenesis on
the screening media. A strain, MUT23 , with abnormal slow growth
morphology was found to delay parasitism by £. virginiana. The
particular morphology was not due to auxotrophy, because this
strain displayed normal hyphae when glucose was used as the sole
One interesting phenomenon was that MUT23 showed an extensive
clearing zone around the colony on colloidal chitin agar after
20-25 d. On the same conditions, wild type strain did not show this
phenotype. In addition, the MUT23 strain produced the same normal
hypha as the wild type strain when it was grown on colloidal chitin
agar. The MUT23 was also able to produce more spores on colloidal
chitin agar than on malt-yeast extract and minimal media.
The parasite germ tubes formed appressoria at the point of
contact on the cell surface of wild type and MUT23 grown for 6 days
cell surface but not on the cel surface of MUT23 grown for 2 days.
Thus, interaction between MUT23 strain and the mycoparasite was
dependent on MUT23 age. The effect of MUT23 filtrate on germination
of the parasite was tested. Lysis of germinated spores of the
parasite were observed in concentrated MUT23 filtered solution.
MUT23 was compared to the wild type strain for their chitinase
production in sUbmerged culture. The chitinase isozymes of both
wild type and MUT23 were shown by immunoblotting. Eight distinct
chitinase molecules were detected. MUT23 showed markedly higher
chitinase activity than the wild type cultured in chitin-containing
medium. Maximum chitinase activities of MUT23 were 13.5 fold higher
at 20 day of the culture then that of wild type.||en_US
|dc.title||Isolation and characterization of a chitinase-secreting mutant of mortierella pusilla with altered interaction with the mycoparasite piptocephalis virginiana||en_US
|dc.type||Electronic Thesis or Dissertation||en_US
|dc.degree.name||M.Sc. Biological Sciences||en_US
|dc.contributor.department||Department of Biological Sciences||en_US
|dc.degree.discipline||Faculty of Mathematics and Science||en_US