Bioactive Potential of Some Bacillus thuringiensis Strains from Macapá, Amazon, Brazil, Against the Housefly Musca domestica (Diptera: Muscidae) Under Laboratory Conditions

The high pathogenic activity of <i>Bacillus thuringiensis</i> (<i>Bt</i>) strains against various insect orders has positioned it as the most effective, environmentally safe, and sustainable approach to integrated insect management. We aimed to identify <i>Bt</i> strains capable of effectively controlling the housefly <i>Musca domestica</i>, a species of significant medical, veterinary, and public health concern. Twelve <i>Bt</i> strains from Macapá, Brazil, were tested against housefly larvae. PCR was employed to detect genes encoding Cry and Cyt proteins and Vips. Six strains exhibited 70 to 100% larval mortality, with five containing <i>cry</i> genes, none harboring <i>cyt</i> genes, and four carrying <i>vip</i> genes. Scanning electron microscopy revealed the production of crystal inclusions with distinct morphologies: spherical (TR4J, SOL5DM, SOL6RN), cuboidal and bipyramidal (TRO1TN and TRO2MQ), and spherical and bipyramidal (UNI2MA). The potential presence of genes from the <i>cry1</i>, <i>cry2</i>, <i>vip1</i>, and <i>vip3</i> families suggests that these strains also exhibit bioinsecticidal activity against other muscoid flies and insect pests across various orders. This study underscores the bioactive potential of these Brazilian <i>Bt</i> strains for developing new bioinsecticides.