Seleção de bacillus spp. da Amazonia brasileira portadores do gene Chi (quitinase) para o controle biológico de Aedes (stegomyia) aegypti(Linnaeus, 1762).

Abstract

The Aedes aegypti mosquito is an important vector in the transmission of dengue virus, urban yellow fever, zika and chikungunya. The main tool used to control this vector is conventional chemical insecticides. However, continuous use causes many negative factors, such as environmental contamination and selection of resistant populations. In this sense, the biological control by microorganisms is a biotechnological alternative in the control of vectors, mainly the bioinseticidas formulated with bacteria of the genus Bacillus. Considering the diversity of Bacillus, members of this genus are capable of synthesizing bioinsecticidal biomolecules against different orders of insects. In addition, they are able to synthesize biopolymers, antibiotics and enzymes such as chitinase expressed by the chi gene. These enzymes have the ability to hydrolyze β-1,4 glycosidic bonds between the chitin polymer units. After ingestion by the larvae of the insect, it causes degradation of the peritrophic membrane that separates the epithelium from the middle intestine of the intestinal lumen, whose main component is chitin. This factor is a favorable requirement for its use in the control programs of insect vectors and agricultural pests. In this study, 124 bacterial strains isolated from soil, water, plant and insect from different Amazonian environments were used. All strains were identified by phenotypic characteristics as belonging to the bacilli group, being one hundred and fourteen (91.4%) Gram positive and ten (8.6%) Gram negative. In the molecular identification by amplification and sequencing of the 16S (rDNA) gene, 33 lines were identified, 27 belonging to the genus Bacillus, 4 to the genus Serratia, 1 to the genus Paenibacillus and 1 to the genus Achromobacter. In the molecular detection of the chi gene, six lineages (4.5%), BTAM27LB, 103PHAISP2, BTAM138LB, BTAM18NA, K2NA and R11ISP2 showed positive amplification, of which two were identified, BTAM 27- Bacillus sp. and R11ISP2-Bacillus amyloliquefaciens. In the selective bioassays of 124 lineages, 21 showed activity in Aedes aegypti larvae. The bioassays with the metabolic extracts produced by these 21 lineages cultivated in NA, LB and ISP2 medium demonstrated that 7 presented pathogenicity in the lyophilized culture and only 3 in the filtered supernatant. In another step, metabolic extracts produced by 9 strains cultured in chitin medium were evaluated, of which only 1 presented mortality in both the supernatant and lyophilized culture, presenting values corresponding to 100%. Thus, the selected strains present potential for the development of microbial bioinsecticides.