Plasmid Dna Characterization of Indigenous Bacteria Useful in Biological Control of Mosquitoes Vectors of Malaria

From different zones of Colombia (Llanos Orientales, Pacífico, Costa Atlántica y Sabana de Bogotá) 269 strains of sporulated bacilii were isolated. In order to evaluate the toxicity of selected strains, a biological assay against third-instar larvae of Culex quinquefasciatus, Anopheles albimanus and Aedes aegypti was made. Twenty two strains showed 80-100% of mortality between 24 and 72 hours, of which 19 were classified as Bacillus sphaericus and three as B. thuringiensis. For determination of the absence or presence of the plasmidic DNA in these pathogenic strains a plasmid isolation and electrophoresis in agarose gel were made in which it was observed that 20 of 22 strains had large plasmids. To correlate the presence of these plasmids with the toxicity of the 20 strains a treatement of curing using high temperature was undertaken. It was found that four indigenous strains have plasmids linked with toxicity and there is a variability in the stability of plasmids among different strains.