Hk. Ahmed et al., OPTIMIZATION OF MOSQUITOCIDAL TOXIN SYNTHESIS FROM BACILLUS-SPHAERICUS USING GENE FUSIONS, World journal of microbiology & biotechnology, 12(1), 1996, pp. 7-11
beta-Galactosidase gene fusions have been used to monitor the progress
of mosquito-larvicidal-toxin gene expression in Bacillus sphaericus s
train 2362. beta-Galactosidase estimation in cells from late-growth-ph
ase batch cultures was compared with larvicidal toxicity after incubat
ion for 48 h. Conditions which promoted efficient sporulation, such as
plentiful trace elements and relatively crude protein sources (soybea
n or cottonseed flours), enhanced reporter gene expression and provide
d high toxicity. However, acetate, which repressed sporulation, simila
rly repressed binary toxin yield. Gene fusions to the binary and 100-k
Da toxin genes of B. sphaericus could be useful for the rapid screenin
g of fermentation conditions for the local production of this larvicid
al bacterium but, in view of the poor correlation with toxicity at hig
h toxicity levels, such experiments should be confirmed with bioassays
.