No abstract

This work aimed to select potentially useful rhizobacteria for the control of Meloidogyne exigua, a widely disseminated root-knot nematode found in Brazilian coffee fields. Initially, crude metabolites produced in liquid medium by 69 isolated rhizobacteria strains (previously obtained from several plants collected in the south of Minas Gerais State, Brazil) were tested in vitro for lethality towards M. exigua second stage juveniles (J 2 ). Substances produced by strains of Bacillus cereus, B. megaterium, B. pumilus, B. thuringiensis, Enterobacter asburiae, E. cloacae and Paenibacillus macerans caused high mortality in J 2 . Subsequently, the ten most active crude metabolites were selected and assessed for nematicidal activity in a biotest with M. exiguainoculated coffee plants. Although strains of B. cereus, B. pumilus and P. macerans caused a significant reduction in the number of root galls and/ or nematode eggs per plant 90 days after treatment, the best results were obtained with the application of B. megaterium strain 54-06.

Esta pesquisa foi conduzida com o objetivo de verificar o melhor nível de torta de dendê na dieta de cordeiros por meio da avaliação da condição hepática. Foram utilizados 32 cordeiros Santa Inês não-castrados distribuídos em quatro dietas com 0,0; 6,5; 13,0 e 19,5% de torta de dendê na matéria seca (MS). A cada 15 dias, foram coletadas amostras de sangue dos animais, totalizando cinco coletas em todo o período experimental. Foram determinados os teores de triglicérides, colesterol, proteínas totais, albumina e globulina; as atividades das enzimas alanina aminotransferase (ALT), aspartatoaminotransferase (AST) e gama glutamiltransferase (GGT); e as concentrações séricas de bilirrubina total, direta e indireta. O aumento do percentual de torta de dendê na dieta não influenciou a concentração de triglicérides, cujo valor médio foi de 40,57 mg/dL, mas elevou as concentrações de colesterol. Também não ocasionou diferença no conteúdo de proteínas totais, mas teve efeito quadrático crescente nos níveis de albumina e ureia e efeito linear decrescente nos níveis de globulinas. Não foram observadas diferenças estatísticas nas atividades das enzimas alanina-aminotransferase, aspartato-aminotransferase e gama-glutamiltransferase, que foram de 6,40; 37,59 e 62,38 UI/L, respectivamente. Igualmente, não foi detectada influência sobre a bilirrubina total, direta e indireta, cujas médias foram de 0,50; 0,11; e 0,38 mg/dL, respectivamente. O uso de torta de dendê em níveis de até 19,5% da dieta não causa transtornos metabólicos hepáticos em cordeiros.

To contribute to the development of products to control Meloidogyne exigua, the bacteria Bacillus cereus and B. subtilis were cultivated in liquid medium to produce metabolites active against this plant-parasitic nematode. Fractionation of the crude dichloromethane extracts obtained from the cultures afforded uracil, 9H-purine and dihydrouracil. All compounds were active against M. exigua, the latter being the most efficient. This substance presented a LC 50 of 204 µg/mL against the nematode, while a LC 50 of 260 µg/mL was observed for the commercial nematicide carbofuran. A search for protein-ligand complexes in which the ligands were structurally similar to dihydrouracil resulted in the selection of phosphoribosyltransferases, the sequences of which were used in an in silico search in the genome of M. incognita for a similar sequence of amino acids. The resulting sequence was modelled and dihydrouracil and 9H-purine were inserted in the active site of this putative phosphoribosyltransferase resulting in protein-ligand complexes that underwent molecular dynamics simulations. Calculation of the binding free-energies of these complexes revealed that the dissociation constant of dihydrouracil and 9H-purine to this protein is around 8.3 x 10 -7 and 1.6 x 10 -6 M, respectively. Consequently, these substances and the putative phosphoribosyltransferase are promising for the development of new products to control M. exigua.

No abstract