AGBAA. Artículos de Investigación

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Examinando AGBAA. Artículos de Investigación por Materia "Bacillus thuringiensis"

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  • Publicación
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    Caracterizaci ón molecular de genes cry1, cry2, cry3 y cry4 en aislados de Bacillus thuringiensis y determinación de su actividad bioinsecticida en larvas de Aedes aegypti
    (2013-02-20) Galvis Serrano, Nestor Fabián
    Chemical insecticides can be toxic and cause environmental degradation. Therefore, biological control of insects represents an alternative of low ecological impact. Bacillus thuringiensis is a spore-forming Gram-positive bacterium that produces parasporal crystals of a proteic nature, formed by delta endotoxins that are toxic to a large number of insects and are biodegradable and innocuous to other species. In the present work 13 native strains of B. thuringiensis were isolated from soil samples and identified by selective methods and the BBL CRYSTAL method. In the molecular characterization utilizing specific primers for the identification of cry1, cry2, cry3 y cry4 genes, eight isolates presented the cry3 gene and two presented the cry2 gene. These two latter isolates were used in a bioassay on Aedes aegypti larvae to determine their toxic effect, showing that the preliminary toxicity essay of the BtUDES2 isolate presented a lethality of 56.67%. When determining the lethal concentration of this same isolate, an average lethal concentration of 11.4333ng·ml-1 and a total lethal concentration of 17.1542ng·ml-1 were found.
  • Publicación
    Acceso abierto
    Preferential Protection of Domains II and III of Bacillus thuringiensis Cry1Aa Toxin by Brush Border Membrane Vesicles
    (2010-12) Hussain, Syed-Rehan A.; Florez, Alvaro M.; Dean, Donald H.; Alzate, Oscar
    The surface exposed Leucine 371 on loop 2 of domain II, in Cry1Aa toxin, was mutated to Lysine to generate the trypsin-sensitive mutant, L371K. Upon trypsin digestion L371K is cleaved into approxima-tely 37 and 26 kDa fragments. These are separable on SDS-PAGE, but remain as a single molecule of 65 kDa upon purification by liquid chromatography. The larger fragment is domain I and a portion of domain II (amino acid residues 1 to 371). The smaller 26-kDa polypeptide is the remainder of domain II and domain III (amino acids 372 to 609). When the mutant toxin was treated with high dose of M. sexta gut juice both fragments were degraded. However, when incubated with M. sexta BBMV, the 26 kDa fragment (domains II and III) was preferentially protected from gut juice proteases. As previously reported, wild type Cry1Aa toxin was also protected against degradation by gut juice proteases when incubated with M. sexta BBMV. On the contrary, when mouse BBMV was added to the reaction mixture neither Cry1Aa nor L371K toxins showed resistance to M. sexta gut juice proteases and were degraded. Since the whole Cry1Aa toxin and most of the domain II and domain III of L371K are protected from proteases in the presence of BBMV of the target insect, we suggest that the insertion of the toxin into the membrane is complex and involves all three domains.