Toxicity to fourth instar Culex quinquefasciatus ofBacillus thuringiensis subsp. israelensis (Bti) strains that produce high levels of the B. sphaericus (Bs) binary toxin in comparison with wild-type Bti and Bs
| Bacterial strain . | Toxin composition . | LC50 (ng ml−1) . | Improvementa . |
|---|---|---|---|
| Bti IPS-82 + Bs Bin | Cry4A + Cry4B + Cry11A + Cyt1A + Bs Bin | 1.5±0.4 | 13× |
| Bti 4Q7 + Bs Bin | Bs Bin | 1.4±0.4 | 10× |
| Bti IPS-82 | Cry4A + Cry4B + Cry11A + Cyt1A | 19.5±3.5 | |
| Bs 2362 | Bs Bin | 15.0±3.4 |
| Bacterial strain . | Toxin composition . | LC50 (ng ml−1) . | Improvementa . |
|---|---|---|---|
| Bti IPS-82 + Bs Bin | Cry4A + Cry4B + Cry11A + Cyt1A + Bs Bin | 1.5±0.4 | 13× |
| Bti 4Q7 + Bs Bin | Bs Bin | 1.4±0.4 | 10× |
| Bti IPS-82 | Cry4A + Cry4B + Cry11A + Cyt1A | 19.5±3.5 | |
| Bs 2362 | Bs Bin | 15.0±3.4 |
Improvement represents the factor by which the toxicity per unit mass of lyophilized fermentation product is improved compared with that of the wild-type strains. The Bti IPS-82 + Bs Bin strain is compared with Bti IPS-82,a wild-type strain, and the Bti 4Q7 + Bs Bin strain is compared with Bs 2362,a wild-type strain.