B. KESINI*, K. DEVAKI, M.S.V. CHALAM, V.L.N REDDY, B. RAMANAMURTHY AND
Department of Entomology, S.V. Agricultural College, ANGRAU, Tirupati
The parasporal crystal toxins produced by Bacillus thuringiensis are the most widely used natural insecticides in pest
control in agriculture and vector control of public health. B. thuringiensis was isolated from soil samples of Tirupati region using sodium acetate selection method. The soil samples were buffered with 0.5M sodium acetate followed by heat shock at 80oC and serial diluted up to 10-5 for eliminating non-spore forming bacteria and other microbes in the culture and then grown on LBA medium. After 24 hr of incubation, the colonies which were round, creamish with fried-egg appearance were produced. A total of 71 colonies from 100 soil samples were tested for Gram staining and observed 56 Gram positive bacteria with rod shaped structure. These 56 Gram positive cultures resulted in 42 endospore producing cultures and finally 32 crystal producing B. thuringiensis cultures were identified out of which 16 were bipyramidal, 9 were rhomboidal and 7 were spherical.
B. thuringiensis, Collection, Isolation, Soil samples