Identificación molecular de bacterias resistentes al arsénico (As) y al cromo (Cr) de la microcuenca del río Gala del cantón Camilo Ponce Enríquez

Abstract

The aim of this research was the molecular identification of bacteria with metabolic capacity to resist high concentrations of Arsenic (As) and Chromium (Cr) present in water samples from Gala River micro-watershed, located in Camilo Ponce Enriquez county, Azuay province. The corresponding bacterial isolation was performed through an extensive surface sowing in PCA culture medium, these samples were incubated at 25 degrees Celsius. Considering the macroscopic morphological characterization as a starting point, 27 representative colonies were selected to perform consecutive sowings or copies to obtain axenic cultures. After performing nine copies of pure cultures, sensitivity analyses were performed for arsenic with arsenic trioxide from 0.1 to 100 ppm, obtaining 22 resistant strains, while for chromium with chromium dioxide, 21 resistant strains from 0.5 to 50,000 ppm were obtained. DNA extraction and purification were performed through conventional methods which were based on the application of pipes containing beads with buffer, β-mercaptoethanol extraction. On the other hand, bacterial sampling and its homogenization in vortex to release genetic material was carried out. DNA was also quantified through microvolume spectrophotometry and its integrity was evaluated by agarose gel electrophoresis to subsequently perform PCR. The amplicons obtained were sequenced in the Macrogen laboratory where sequences were obtained and matched in BLAST bioinformatic analysis; thus, 16 bacterial species were identified. The most important bacterial species belonging to genera were: Enterobacter sp, Pseudomonas sp, Aeromonas sp, Acinetobacter sp and Bacillus sp, which have relation with contamination caused by heavy metal removal treatments. It is recommended to investigate the resistance of these microorganisms in other heavy metals, especially in those related to mining activities.