Caracterização bioquímica e molecular de bactérias associadas a Oryza sativa L. produtoras de biocompostos

Abstract

Bacteria associated with rice and crops of agricultural interest are common known as plant growth promoting rhizobacteria. These constitute a diverse and numerous group of soil bacteria, which, when associated with these plants, act directly and indirectly in their growth, besides possessing great biotechnological potential. Thus, the goal of this work was to perform the morphological, biochemical and genetic characterization of bacterial isolates associated with the rice plant (Oryza sativa L.) that produce biocompounds. A total of 22 isolates were selected using the yeastextract mannitol (YMA) semi-selective medium. The characterization of the isolates was performed: 1) by macroscopic aspects observed on the colonies; 2) biochemical characterization (resistance to antibiotics, use of carbon sources, hydrolytic enzymes production, inorganic phosphate solubilization and detection of siderophores) and 3) molecular characterization (16S-23S rRNA intergenic analysis). Among the characteristics of the colonies there was a dominance of isolates fast-growing (68%), with mucus production (73%) and had viscous colony (68%). For biochemical assays 90% of the rice isolates used the monosaccharides and disaccharides. All the isolates showed growth in medium with nalidixic acid and 91% were more sensitive to the streptomycin. For Enzymatic assays 95 % of the isolates were positive for catalase, 41% were positive for proteases, 36% cellulose, 32% amylases, 23% lipases and 59 % for P solubilization ability. 27% of the isolates were able to produce siderophores. From the biochemical assays, it was possible to observe that 86.3% of the isolates are potential plant growth promoting, with three promising isolates R59, R68 and R141. Intergenic analysis (16-23S rRNA) revealed a genetic diversity, more than one fragment of different sizes indicating variability of the region among the evaluated isolates. Thus, the results suggest high metabolic and genetic diversity of the isolates associated with the rice plant, and some at them are potential candidates for prospecting studies for the production of bioproducts and plant growth promoting.