Production of asporogenous mutants of Bacillus sphaericus 2362 in continuous culture.
OBJECTIVE
To report the production of asporogenous mutants (Spo-) of Bacillus sphaericus 2362 in continuous culture.


RESULTS
Microbial culture samples were taken at 0.05 h-1 dilution rate and plated out on nutrient agar plates. Translucent colonies were obtained with vegetative morphology under phase contrast microscope. Heat resistance evaluations at different temperature settings showed that the Spo- mutants had lower heat resistance than the Spo+ wild type. Western blots analyses carried out on both wild type and the mutants indicated the presence of binary protein toxins of 42 and 51 kDa in both. Bioassays carried out on the wild type and the Spo- mutants against mosquitoes showed the mutants to be 100-fold less toxic in comparison to the wild type.


CONCLUSIONS
Existence and production of asporogenous mutants of Bacillus sphaericus 2362 in continuous culture at low dilution rates is demonstrated by this study. The organism's ability to produce toxins appears to be significantly reduced by the mutational process.


CONCLUSIONS
The production of asporogenous mutants had not been reported previously among strains of Bacillus sphaericus. The present report on the toxigenic capability of asporogenous mutants also raises the possibility of using continuous culture to significantly improve the productivity of toxin production in future.
Idachaba
M A
MA
Department of Biotechnology, The University of New South Wales, Sydney, NSW, Australia. idachaba@acd.tusk.edu
Rogers
P L
PL
D000818:Animals; D001407:Bacillus / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D001427:Bacterial Toxins / Q000096:biosynthesis / Q000633:toxicity; D015169:Colony Count, Microbial; D003465:Culex / Q000382:microbiology / Q000502:physiology; D003470:Culture Media; D006358:Hot Temperature; D009154:Mutation; D013171:Spores, Bacterial
D001427:Bacterial Toxins; D003470:Culture Media