Estudo de caracterização genética e produção de pigmentos tipo melanina de bactérias endofíticas isoladas de milho (Zea mays L.)

Abstract

Inoculation of maize with Plant-Growth-Promoting Rhizobacteria (PGPR) can improve the growth of this cultivar, reduce the use of nitrogenous fertilizers and the costs of production, and reduce the negative impacts to the environment. Moreover, the production of pigments, such as melanin, by these bacteria might have promising commercial applications in food industries, pharmaceutical, cosmetics and textiles products. The general objective of this work was to study genetic and biochemical characterization of 20 endophytic bacteria isolated from maize (Zea mays L.) grown in the Cerrado Goiás to observe the genetic diversity, identify bacteria that can be used as inoculants and check production melanin-like pigment by these bacteria. For the diversity study, analysis was performed with molecular markers: 16S-23S rRNA intergenic spacer sequences, dispersed repetitive extragenic palindromic DNA sequences (REP), genes atpD, glnII e 16S rRNA, 16S rRNA gene restriction; gene melA. It was also performed the partial 16S rRNA gene sequencing to identify isolated from maize. To observe the production of pigments melanin-like, bacteria were grown on potato liquid culture media, with L-tryptophan and copper sulfate, and was subsequently identified the production of melanin-like pigments over the peak of absorbance in a spectrophotometer at wavelengths of 300, 350 and 400 nm. The concentration of melanin-like pigments was calculated from a standard line, from the readings obtained using synthetic melanin at different concentrations at 400 nm. By the similarity analysis using molecular markers was observed great genetic diversity of bacteria studied which was confirmed by partial sequencing of the 16S rRNA gene, because were identified bacteria of Agrobacterium, Burkholderia and Cedecea genera. These identified bacteria may be used in the inoculants formulation for maize varieties grown in Brazil. For pigment production, the maize isolated MT45 showed high production of melanin-like and may be used to obtain bioproducts.