The Characterization of Bacillus thuringiensis from soil habitat of Auky Island, Padaido District in Biak Numfor Regency and Its Toxicity against Mosquito Larva of Anopheles sp

Abstract

Bacillus thuringiensis (Bt) is bacteria that produce protein crystals as an insecticidal against various vector diseases in plants and animals including humans. The purpose of this research is to discover the local isolate toxicity of B. thuringiensis from Auky Island Padaido District in Biak Numfor Regency against mosquito larva Anopheles sp., as well as to discover the local isolate of B. thuringiensis with toxicity ≥85 of laboratory scale. The method used in the research is toxicity detection method where 1ose colony inserted into a container containing 200 mL sterile soil water and 20 larvae of Anopheles instar 3 for 24 h. The percentage of larval deaths is calculated by the number of dead larvae divided by the total number of larvae multiplied by 100%. The result of the research shows three isolates (ABNP 8, ABNP P and ABNP 11) of isolate local B. thuringiensis which the toxicity is ≥ 85%. The difference in toxicity may becaused by the difference of strain, the ability of the enzymes in larvae stomach to dissolve δ endotoxin, in which when dissolved in insect gut, it will turn into shorter insecticidal peptides (27-149 kd) and subsequently interact with epithelium cells in the larval midgut and cause pores formation (very small holes) inside the channel digestion membrane and disrupt the osmotic balance, the cell swells and eventually ruptures causing the death of larvae. The difference in toxicity can also be caused by the difference of molecular weight of Gen Cry, in this study the probability of isolates whose toxicity ≥85 has the gen Cry IV b and IV c. Therefore, this study should be continued to determine the genotype of toxic causes of Anopheles larvae.