FIG 6.

Any gene deletion in the Cry operon results in loss of toxicity. (A) Three gene deletions were made. In the first construct, pCry16, only Cry16A was expressed (Fig. 5), while in the second, CryO/Δ17.1, only cbm17.1 was deleted and in the third, pCry16/17, both cbm17 genes were deleted. The last two were derived from pCryO by restriction with PacI (P) and NcoI (N), respectively. Each of the constructs is under the control of the Cyt1A promoter and includes a 3′ terminator identical to the Cry operon construct in Fig. 3. (B) The Cry16A toxin was observed in the recombinant B. thuringiensis CryO, recombinant B. thuringiensis pCryO/Δ17.1, and recombinant B. thuringiensis pCry16/17 cultures. The recombinant B. thuringiensis CryO construct also shows expression of the Cbm17.1 protein at 48 to 72 h, as observed at 24 h (Fig. 3).