Isolation and characterization of Bacillus thuringiensis strains from soil samples from kakamega and Machakos districts in Kenya

Abstract

Twelve isolates of Bacillus thuringiensis were obtained from soil samples collected from farmers' fields in Kakamega and Machakos districts. Soil samples from Machakos yielded more B. thuringiensis isolates t han those from Kakamega. Three isolates K13-1, 12F-K and K10-2 were obtained from Kakamega soil samples. Isolates 1M, 44M, VM -10, V15-M, 34M, 35M, V14-M, V15-M, V24-M were obtained from Machakos soil samples. The morphological characterization indicated t hat the B. thuringiensis strains were different with regard to rod length. However, there were no variations with regard to the rod width and crystal (parasporal body) shape of the different isolates. The crystals of all the isolates were bipyramidal in shape. pH tolerance was characteristically different for the different B. thuringiensis isolates. After preliminary screening seven of the isolates (1M, 12F-K, K10-2, VM -10, 44M, V14-M and V24-M, were found to be highly potent and analysis on Sodium dodecyl sulfate- polyacrylamide gel electrophoresis of crystalspore complex of the seven isolates, indicated the presence of three major protein bands of molecular weight (Mr), ~28,000, ~ 65,000 and ~130,000 except for isolate 1M which did not show the ~130,000 protein .