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