REGULATION OF MOSQUITOCIDAL TOXIN SYNTHESIS IN BACILLUS-SPHAERICUS

Translational lacZ fusions to the promoters of the parasporal, crystal protein (binary toxin) and 100-kDa ADP-ribosylating mosquitocidal tox in genes of Bacillus sphaericus were prepared and expression of the to xin genes monitored as beta-galactosidase activity, Transcription of t he crystal protein gene fusion began immediately before the end of exp onential growth and continued into stationary phase in both B. sphaeri cus and Bacillus subtilis but accompanied exponential-phase growth in Escherichia coli. Expression of this fusion was severley delayed in a B. subtilis spo0A mutant and decreased relative to the wild type in a B. subtilis spoIIAC background. beta-Galactosidase activity from the 1 00-kDa toxin gene fusion was restricted to early exponential phase in B. sphaericus, but in B. subtilis it continued into late exponential p hase. Expression was about eightfold lower in B. sphaericus than B. su btilis suggesting an element of negative control in the native host.