Evaluación de la tolerancia a metales pesados: cobalto, mercurio y plomo en microorganismos aislados de laguna de Ozogoche en la parroquia Achupallas del cantón Alausí.

Abstract

The objective of this research was to isolate microorganisms from the “Laguna de Ozogoche” to assess tolerance to heavy metals: cobalt, mercury, and lead. Six samples taken randomly at different points of the lagoon were processed, which were inoculated by the technique of seeding on surface in three different media types: Medium without selective pressure prepared with sterile distilled water (PCA-), medium prepared with water from the lagoon (AGL) and medium with selective pressure (PCA +) supplemented with Lead Nitrate 25 ug / mL, were incubated at 9 ºC and 35ºC. Isolation of representative microorganisms was carried out and the number of bacteria capable of growing at the two temperatures evaluated was determined. Of these, 187 clones were selected, four rings were made, for their adaptation and stabilization. The last ring was sown by exhaustion and taken a total of 69 bacterial clones, on them, the Gram stain was performed; the predominance of Gram-negative bacilli was observed at 9ºC (75%) and at 54ºC it was 54.1%. In the case of Gram-positive bacilli, 32.4% was obtained at 35 ° C, while at 3 ° C, 3% was found. These clones were subjected to tolerance tests for metals Co, Hg and Pb in increasing concentrations (50, 100, 250, 500,750, 1000.2500 and 4000 ug/ml), resulting in several tolerance levels for the isolated clones; 2 clones showed tolerance up to 750 ug/ml cobalt, 5 up to 250 ug/ml mercury and 6 up to 4000 ug/ml of lead. Biochemical tests were performed on the 13 clones that showed the highest tolerance, identifying the genera Clostridium, Corynebacterium, Klebsiella, Micrococcus spp and Pseudomonas spp. It was concluded that psychrotolerant bacteria resistant to heavy metals were isolated from the water of the Ozogoche lagoon.