Caracterização morfofisiológica e genética de bactérias endofíticas isoladas de milho (Zea mays L.)

Abstract

Whereas plants grown maize ( Zea mays L. ) is the most important grain of the American continent , both in food and in the economy. Many researchers have shown that efficient diazotrophs can contribute positively to the development of corn . Genetic characterization of microorganisms allows deepening the taxonomic , physiological , ecological and economic studies of these living beings . The aim of this work was the characterization and genetic Morphophysiological twenty bacteria isolated from corn for later use as promoting rhizobacteria to plant growth ( PGPR ) . To study the physical and physiological characteristics of the colonies as the capacity utilization of carbon sources 13 and testing for the presence of enzymes ( catalase , protease , citrate lyase and urease ) and the ability to solubilize inorganic phosphate was observed. Genetic analysis by PCR of 16S rRNA intergenic 16S - 23S rRNA region and the BOX of 20 bacteria and reference strains SEMIA 5079 ( Bradyhizobium japonicum ) , SEMIA 6161 ( Sinorhizobium freedii ) , SEMIA 4077 ( Rhizobium tropici ) and SEMIA 3012 ( Rhizobium leguminosarum ) . The results of 20 tests and bacteria reference strains were analyzed for similarity using the Jaccard coefficient . By morphological data 6 groups were observed for the studied bacteria . For the tests using carbon sources bacteria were positive for all tested media . For the presence of enzymes, 50 % were positive catalase , citrate positive 95.8 % , 20.8 % positive urease , 29.2 % protein hydrolases and 50 % are solubilizing inorganic phosphate for both media tested . Using cluster analysis using biochemical data was possible to characterize 7 groups with similarity around 70 %. For these results we observed the great metabolic diversity of bacteria studied . For the region - BOX can 9 to characterize groups of bacteria with around 50% similarity. Amplification of 23S rRNA - intergênica16S region showed significant variation in the number and size of the fragments . By applying the method to ARDRA 16S rRNA gene xxiii 7 groups with a broad profile of polymorphism were characterized . These results demonstrate the genetic variability of bacteria associated with plant development . The morphological , biochemical and molecular characterizations may help to select candidates to be bacteria used for inoculation in vitro assays and field for maize in Goias Cerrado.