Isolation and characterization of highly potent mosquitocidal bacilli from Egyptian environment

Abstract

A number of 359 Bacilli isolates were obtained from soil samples collected from different Egyptian governorates. Five Egyptian isolates identified as Lysinibacillus sphaericus yielded highly potent mosquitocidal toxicity. These isolates (Ls 9B24, Ls 3B3, Ls 2LB10, Ls 4N9 andLs 4LB19) were obtained from soils of Alexandria, KafrEl- Sheikh, New valley and El- Gharbeya governorates respectively. The values of LC50 andLC90 of these isolates showed that the most active mosquitocidal isolate was Ls 9B24 and it was more active than the international standard strain Lysinibacillus sphaericus 2362. It was concluded that NYSM medium supported the highest growth, sporulation and toxicity of Ls 9B24 and Lysinibacillus sphaericus 2362. Physiological studies onLs 9B24 in comparison wiih Lysinibacillus sphaericus 2362 grown in NYSM medium showed that buffering the medium at pH 6.5-7.0 significantly enhanced the toxicity of both tested cultures. Addition of NYSM salts at 4 and 1-2% enhanced the toxicity of Ls 9B24 and Lysinibacillus sphaericus 2362, respectively. Aeration level 24:1 air: medium was the optimum for maximum toxicity produced by both cultures under study. Optimum temperature for the growth, sporulation and toxin formation of tested cultures was 30°C. At 37°C, the mosquitocidal activity dramatically decreased. The maximum toxicity was obtained after 3 days of incubation for both organisms. © 2013 Asian Network for Scientific Information.