5-L culture was washed twice with 1 M NaCl and 10 mM EDTA, pH 7.0, and twice with double-distilled water. The pellet was dissolved in sterile water and sonicated for 5 min with 3-s pulses at 30% amplitude in a Branson digital sonifier (model 250, Branson Ultrasonics Corporation, CT).

The sonicated suspension was centrifuged at 15 000 g for 30 min. The supernatant PKC inhibitor was discarded and the pellet was dissolved in 50 mM NaOH. This suspension was incubated on ice for 3 h with gentle shaking. The suspension was centrifuged at 15 000 g for 20 min at 4 °C. The supernatants containing the solubilized binary toxins were dialyzed overnight against buffer A (25 mM Tris-HCl, 10 mM NaCl, 2 mM DTT, pH 9.0). The dialyzed suspension was centrifuged at 15 000 g for 20 min at 4 °C and the supernatant was loaded on a Q-sepharose column EPZ-6438 ic50 (Bio-Rad laboratories, Hercules, CA). The bound protein was eluted with a linear gradient of 10–1000 mM NaCl over a six-column volume. The binary proteins coeluted at around 300 mM NaCl concentration. The eluted protein fractions were analyzed on 12% sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The pure protein fractions were pooled and dialyzed extensively against buffer A. After dialysis, the pooled fractions were concentrated to ∼2 mg mL−1 and loaded on to a Superdex™ 200 10/300 GL column (GE Healthcare Bio-Sciences, Uppsala, Sweden) for further purification. The purified fractions were further resolved on 12% SDS-PAGE. The

purified protein was dialyzed against 25 mM Tris-HCl, pH 8.0, 10 mM NaCl buffer, the protein was estimated using modified Lowry’s protocol and then tested why for toxicity against third-instar larvae of C. quinquefasciatus. Different concentrations of purified binary proteins, along with control and buffer control, were tested in 10 mL tap water containing

10 third-instar C. quinquefasciatus larvae in each beaker (10 mL), with three replications for each concentration, and experiments were repeated three times. The total larval mortality was scored after 48 h of treatment. Mortality data were analyzed using probit analysis and the LC50 values were calculated at a 95% confidence limit (spss 12.0 for Windows). TVC of indigenous isolates and standard 1593 and 2362 grown in NB medium were in the range of 3.8–13 × 108 spores mL−1 (Table 1). Among these isolates, a significantly higher TVC (F=710.99; d.f.=4; P<0.05) was obtained with ISPC-8 (1.3 × 109 spores mL−1). The results of the insecticidal activity of different B. sphaericus strains revealed varying virulence patterns against third-instar larvae C. quinquefasciatus (Table 1). The range for LC50 and LC90 values observed for indigenous isolates was 0.68–6.44 × 103 spores mL−1 and 6.85–37.40 × 103 spores mL−1, respectively, whereas the respective LC50 values for standard strains 1593 and 2362 were 1.85 and 1.22 × 103 spores mL−1 and the LC90 values were 15.39 and 20.58 × 103 spores mL−1. This observation indicates that ISPC-8 (LC50 0.