Mosquito larvicidal and hemolytic proteins purified from parasporal inclusions produced by Bacillus thuringiensis strain PG-14 (serotype 8a:8b)

Abstract

Summary Parasporal inclusion (PI) proteins of strain PG-14 of Bacillus thuringiensis subsp. morrisoni (serotype 8a:8b) and the type strain of B. thuringiensis subsp. israelensis (BTI; serotype 14) were compared using sodium dodecyl sulfate Polyacrylamide gel electrophoresis (SDS-PAGE). The PI of strain PG-14 contained two major proteins with molecular masses of approximately 28 and 68 kD, while the PI of strain BTI contained three major proteins of 28, 38, and 68 kD. Of these major proteins, the 38-kD protein was detected in strain BTI only. Two toxic proteins were purified from alkali-solubilized, silkworm gut juice protease-treated PIs of strain PG-14 by Sephadex G-200 gel filtration and DEAE-cellulose column chromatograhy. The molecular masses of the proteins with mosquitocidal and hemolytic activity were 65 kD and 25 kD, respectively. The LD 50 values of mosquitocidal activity for the isolated 65-kD and 25-kD proteins against 2- to 3-day-old larvae of Aedes aegypti were 68.0 ng/ml and 3164.5 ng/ml, respecitvely. The lowest concentrations of 65-kD and 25-kD proteins showing hemolytic activity against sheep red blood cells were 250 μg/ml and 32 μg/ml, respectively.