Improvement of bioinsecticides production through mutagenesis of Bacillus thuringiensis by u.v. and nitrous acid affecting metabolic pathways and/or delta-endotoxin synthesis.
OBJECTIVE
The present work aimed to obtain bioinsecticide over-producing mutants through classical mutagenesis of vegetative cells of Bacillus thuringiensis (Bt) by using u.v. and nitrous acid, and to evidence the involvement of cell metabolism in delta-endotoxin synthesis.


RESULTS
Vegetative cells of Bt were treated by nitrous acid (0.17 mg ml(-1)) or exposed to u.v. rays (emitted at a wave length of 240 nm). The isolated survivors were screened on the basis of the production of delta-endotoxins and biomass in glucose and/or in gruel-based media at two aeration conditions. Bioinsecticide over-producing mutants were obtained with high frequencies because random mutations were shown to affect cell metabolism at different pathways related to the regulation of delta-endotoxin synthesis.


CONCLUSIONS
Classical mutagenesis of Bt cells lead to the isolation of a large variety of delta-endotoxin over-producing mutants that could be classified into six groups based on the location of the mutations, particularly in metabolism pathways and delta-endotoxin synthesis.


CONCLUSIONS
High frequencies of delta-endotoxin over-producing mutants of Bt could be obtained through classical mutagenesis of vegetative cells. This should contribute to a significant reduction of production and utilization costs of Bt bioinsecticides.
Ghribi
D
D
Laboratoire des Biopesticides, Centre de Biotechnologie de Sfax, Sfax, Tunisia.
Zouari
N
N
Jaoua
S
S
D001413:Bacillus thuringiensis / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000096:biosynthesis*; D001427:Bacterial Toxins / Q000096:biosynthesis* / Q000378:metabolism; D018533:Biomass; D003470:Culture Media; D004731:Endotoxins / Q000096:biosynthesis*; D005396:Fish Products; D005947:Glucose / Q000378:metabolism; D006460:Hemolysin Proteins; D007306:Insecticides / Q000378:metabolism*; D016296:Mutagenesis / Q000187:drug effects / Q000528:radiation effects; D009154:Mutation; D009608:Nitrous Acid / Q000378:metabolism*; D010572:Pest Control, Biological; D014466:Ultraviolet Rays
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D003470:Culture Media; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D005947:Glucose; D009608:Nitrous Acid