Plasmid DNA characterization of indigenous bacteria useful in biological control of mosquitoes vectors of malaria

Abstract

From different zones of Colombia (Llanos Orientales, Pacífico, Costa Atlántica y Sabana de Bogotá) 269 strains of sporulated bacilli 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 plasmid DNA in these pathogenic strains 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 treatment of curing using high temperature was undertaken. It was found that four indig­enous strains have plasmids linked with tox­icity and there is variability in the stability of plasmids among different strains.