Inorganic phosphate has a crucial effect on Cry3Aa delta-endotoxin production.
OBJECTIVE
The study aimed at increasing Cry3Aa delta-endotoxin production by a local isolate of Bacillus thuringiensis (B.t. strain Mm2). To this end, different nutritional conditions were tested for their effects on Cry3Aa yields.


RESULTS
Bacillus thuringiensis Mm2 was grown by shaking at 30 degrees C in different media. Samples were taken from the cultures at intervals and used for protein extraction. SDS-PAGE was performed for toxin analysis. Inclusion of inorganic phosphate (Pi) into the Difco's sporulation medium at an increased level of 200 mmol l-1 caused a fivefold increase (from 3 to 15.6 microg ml-1) in toxin production. Omission of FeSO4 from the medium decreased this yield by half. Resuspension experiments suggested catabolite repression of toxin biosynthesis by glucose. The inclusion of high Pi invariably increased toxin synthesis, even in the absence of sugars.


CONCLUSIONS
Inorganic phosphate had the most striking effect on toxin biosynthesis. Iron effect was found to be unique to our isolate whereas Pi effect seemed to be common to the biosynthesis of Cry3Aa-type toxins. Stimulation of toxin synthesis by Pi did not seem to represent a relief from glucose repression.


CONCLUSIONS
Bacillus thuringiensis is the most versatile biopesticide for use in pest management. Regarding cost-effectiveness of related fermentations, high Pi supplement drastically increases Coleoptera-specific toxin synthesis.
Kurt
A
A
Biology Department, Middle East Technical University, Ankara, Turkey.
Ozkan
M
M
Ozcengiz
G
G
D000818:Animals; D001413:Bacillus thuringiensis / Q000254:growth & development* / Q000378:metabolism; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D001517:Coleoptera; D003470:Culture Media; D004731:Endotoxins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006460:Hemolysin Proteins; D007287:Inorganic Chemicals / Q000378:metabolism*; D010572:Pest Control, Biological; D010710:Phosphates / Q000378:metabolism*
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D003470:Culture Media; D004731:Endotoxins; D006460:Hemolysin Proteins; D007287:Inorganic Chemicals; D010710:Phosphates; C030956:insecticidal crystal protein, Bacillus Thuringiensis