Evaluación del potencial de crecimiento de bacterias diazotróficas en un suelo del piedemonte llanero contaminado artificialmente con diésel

Abstract

Oil spills affect the soil microorganism populations; therefore, this research project aims to evaluate the growth potential of nitrogen-fixing bacteria (BLFN), in a soil of the Piedemonte Llanero extracted from the Agricultural Educational Institution Guacavia (IEAG) in the municipality of Cumaral (Meta), artificially contaminated with diesel. The experimental design of the research consists of treatments in triplicate with 2500, 6100 and 9600 mg kg-1 diesel concentrations, plus one control and physicochemical characterization of the soil. The soil in studio has a sandy clay loam texture, bulk density of 1.10 g/cm3, porosity of 51.75%, pH of 5.37, organic matter of 1.69%, total nitrogen of 0.08% and cation exchange capacity of 5.73 cmol/kg. The populations of BLFN were measured at 30, 60 and 90 days after the addition of the diesel, these were reported in CFU g-1 soil, these populations fluctuated from 2.9x105 CFU g-1 (control soil) to 2.4x106 CFU g-1 (6100 mg kg-1 diesel concentration), there were no significant differences between treatments (Tukey, P≤0.05). 27 bacterial strains, mostly gram positive, were obtained, due to the ability of growing in the Rennie modified selective medium for atmospheric nitrogen fixers microorganism insolation. Four strains were selected and identified, using 16S rRNA, matching to the class actinomycetes of the genus Kribbella sp. and Amycolatopsis sp. with an identity of 99 and 98.7% respectively. It was determined that the density of BLFN is responsible of 65% total nitrogen variability in the soil of the different treatments (r=0.809; P≤0.05). Finally, it was determined that the BLFN are present, even under adverse conditions, such as the presence of diesel, therefore, it is recommended for future research to assess directly the capacity of biological fixation of N, the effectiveness in hydrocarbons degradation and even the ability to act as a microbial consortium for the degradation of hydrocarbons.