Investigation of insecticidal activities and characterization of Bacillus thuringiensis strains isolated from soil samples

Recently, biological control studies have became more important due to harmful effects of chemicals on environment and resistances of the insects to these chemicals. The interest of Bacillus thuringiensis strains producing insectisidal proteins as microbial insecticide has increased. Therefore, studies on the isolation of new Bacillus thuringiensis strains for using against the insect pests have became popular. In this study, four B. thuringiensis strains isolated from the soil samples in Giresun Island have been identified as crystal morphology, SDS-PAGE analysis, plasmid profile, cry gene content, fatty acid analysis and biochemical tests. The result of crystal painting of isolates shows that isolates contain bipyramidal and undefined crystals. Polymerase chain reaction (PCR) was performed on isolates by using general primers (cry1, cry2, cry3 and cry4). It is determined that isolates don't contain these kind of cry genes. While examining plasmid profiles of isolates, T1, T2, T3 and T4 have 4, 6, 3, 5 plasmid profiles, respectively. Insecticidal activities of Isolates on Agelastica alni and Ephestia kuehniella larvas researched and the most insecticidal effect by %84,6 death rate in T2 bacteria have seen in the bioassays with Agelastica alni larvas.