EVALUATION OF BIOLOGICAL NITROGEN FIXATION BY ENDOPHYTIC BACTERIA ASSOCIATED WITH Echeveria lauii

Nitrogen is a very important element for the maintenance of the life of all organisms, since it is involved in several metabolic pathways constituting amino acids, proteins and nucleic acids. Together with phosphorus, the amount of nitrogen supplied to plants is the main limiting factor for their development. Therefore, in agriculture, farmers introduce nitrogen mainly in the form of nitrates (NO3) and ammonia (NH3+) and often this introduction is carried out using fertilizers/ chemical fertilizers. However, the indiscriminate use of these chemical fertilizers entails not only an increase in production costs but also causes adverse effects on the environment due to their incorrect disposal. Endophytic microorganisms are those capable of establishing a relationship with a host plant without causing any damage to this plant. These endophytes stimulate plant growth, can act as biological control agents, and produce a variety of natural products. and also to confer some characteristics of importance to the survival of the host. In this work we evaluated the biological nitrogen fixation capacity of fourteen endophytic bacteria (ELP36, ELP37, ELP38, ELP39, ELP40, ELP40, ELP41, ELP43, ELP44, ELP45, ELP46, ELP47, ELP48, ELP49, ELP50) of Echeveria laui. For the detection of biological nitrogen fixation, test tubes containing semi-solid, nitrogen-free Nfb medium (5.0 g.L-1 malic acid, 0.5 g.L-1 K2HPO4, 0.2 g.L-1 MgSO4.7H2O, 0.1 g.L-1 NaCl, 0.02 g.L-1 CaCl2.2H2O, 2 mL micronutrient solution, 2 mL solution of bromothymol blue, 4mL 4M FeEDTA, 1mL solution of vitamins, 4.5 g.L-1 KOH, 1.8 gL-1 Agar, 1000 mL of distilled water, pH 6.8). Bacteria were inoculated in triplicate from cultures grown in TSA medium (Tryptone Soy Agar). They were incubated at 28 ° C for 72 hours. After this period, a growth film appeared close to the surface of the tubes, indicating the ability to fix nitrogen. Fourteen lines showed positive results for nitrogen fixation. Considering the importance of microorganisms that can contribute to plant growth by fixing nitrogen, for example, it is important to carry out the selection of these microorganisms in order to formulate agricultural inoculants, which could contribute to increase the productivity of a given culture, besides improving the quality of the soils, reducing the costs and the quantity of nitrogenous fertilizers, aiming at the environmental preservation.