Cyt1A from Bacillus thuringiensis synergizes activity of Bacillus sphaericus against Aedes aegypti (Diptera : Culicidae)

Bacillus sphaericus is a mosquitocidal bacterium recently developed as a co mmercial larvicide that is used worldwide to control pestiferous and vector mosquitoes. Whereas B, sphaericus is highly active against larvae of Culex and Anopheles mosquitoes, it is virtually nontoxic to Aedes aegypti, an im portant vector species, In the present study, we evaluated the capacity of the cytolytic protein Cyt1A from Bacillus thuringiensis subsp. israelensis to enhance the toxicity of B, sphaericus toward A. aegypti. Various combina tions of these two materials were evaluated, and all were highly toxic. A r atio of 10:1 of B, sphaericus to Cyt1A was 3,600-fold more toxic to A. aegy pti than B, sphaericus alone. Statistical analysis showed this high activit y was due to synergism between the Cyt1A toxin and B. sphaericus, These res ults suggest that Cyt1A could be useful in expanding the host range of B, s phaericus.