Isolamento de Bacillus thuringiensis de amostra de solo e sua toxicidade sobre trofozoítos de Acanthamoeba castellanii

• Ano de defesa: 2018
• Autor(a) principal: Santos, Edclecia Nascimento
• Orientador(a): Jain, Sona Arun
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Programa de Pós-Graduação: Pós-Graduação em Biologia Parasitária
• Palavras-chave em Português: Biologia; Bacillus (Bacteria); Proteínas; Protozoário; Acanthamoeba. B. thuringiensis; delta-endotoxinas; Proteínas cry; Acanthamoeba castellanii. B. thuringiensis
• Palavras-chave em Inglês: Delta endotoxins; Cry proteins; Protozoan; Acanthamoeba castellanii
• Área do conhecimento CNPq: CIENCIAS BIOLOGICAS::PARASITOLOGIA
• Link de acesso: http://ri.ufs.br/jspui/handle/riufs/15719

Bacillus thuringiensis is a Gram-positive non-pathogenic spore-forming bacterium found in different habitats such as soils, plants, dead insects and marine sediments. This bacterium is the producer of several types of secondary metabolites with toxic activity, among them are the crystals of δ-endotoxin produced during sporulation. These proteins are called insecticidal crystal proteins (ICPs) and are distributed in two families: Cry and Cyt. Cry presents toxicity to a wide range of invertebrate organisms and also human cancer cells. B. thuringiensis is thus widely used as a bioinsecticide. Protozoa represent one of the target groups of these toxins, but with studies still scarce. The protozoan Acanthamoeba castellanii is a free-living amoeba, potentially pathogenic and causes diseases such as amoebic keratitis and granulomatous encephalitis amoebic, an illness difficult to diagnose and without specific drugs. This work aimed to isolate strains of B. thuringiensis from the soil and to characterize the Cry toxins encoded by them through toxicity tests against A. castellanii trophozoites. A total of 15 soil samples from different regions of the state were collected, and 150 bacillus like isolates were selected based on their morphological characteristics.After the analysis under microscope, 75 strains withgreater sporulation and presence of parasporal proteins were selected for bioassay. A total of three isolates 66, 69 and 75, showed high amebicidal activity against A. castellanii. After 48 h of interaction between protein and protozoa, the samples presented between 96.24 and 97.8% of cell death in the concentrations of 50 - 100 μg / mL. Under these conditions, the isolates presented IC50 values of 4.1, 4.35 and 8.3 μg/mL, respectively. Our results show that these proteins from B. thuringiensis exerts an amebicidal effect on trophozoites of A. castellanii. However it is necessary to carry out more specific studies so that these toxins can be used as medicine.