Biochemical and molecular characterization of a native mosquitocidal strain of Bacillus thuringiensis from Argentina

BERÓN, C

Foz do Iguassu, Brasil

Congreso; VIII International Colloquium on Invertebrate Pathology and Microbial Control. XXXV Annual Meeting of the SIP. VI International Conference on Bacillus thuringiensis.; 2002

Society of Invertebrate Pathology

As a result of a screening carried out in Argentina, a new native strain of Bacillus thuringiensis (FBt41) was isolated from soil samples of Provincia de Buenos Aires. Phase contrast microscopy of the sporangia revealed the presence of rounded to irregular crystal protein inclusions. The analysis of the protein profile by polyacrylamide gel electrophoresis of the spore-crystal complex showed the presence of several proteins of similar relative abundance. Through laboratory bioassays this strain exhibited a high insecticidal activity against dipteran larvae, specifically Aedes aegypti. No insecticidal activity against coleopterans (Diabrotica speciosa and Tenebrio mollitor), or lepidopterans (Spodoptera frugiperda and Anticarsia gemmatallis) was observed. We used a PCR-based strategy for amplification of DNA fragments with degenerated oligonucleotides homologous to cry genes, followed by Tail-PCR methodology, in order to clone and sequence a toxin strain gene. BLASTp analysis (using the deduced amino-acid sequence of the Cry protein from the FBt41 strain) indicated that it is related to Cry 24Aa protein type. This result was confirmed by using a generated dendogram including the Clustal W method with the PAM 250 residue weight table and representative members of Cry proteins from public data bases. Our data indicate that B. thuringiensis strain FBt 41 is of interest for further studies on the control of A. aegypti, a human disease vector.