In Vitro Evaluation of Rhizosphere Bacteria to Different Mercury Concentrations in Contaminated Agricultural Soils

Abstract

The objective was to isolate rhizosphere bacteria from plant species present in soils contaminated with mercury in the region San Jorge, department de Sucre, Colombia, and to evaluate in vitro their tolerance capacity to different concentrations of mercury. From each sampling site were collected. The concentration of mercury in soil was determined using the instrumental technique of cold vapor atomic absorption spectrophotometry. The amount of rhizosphere bacteria per tissue was determined as CFU/g of soil. The tolerance of endophyte bacterial isolates to different concentrations of mercury was performed in liquid Tris-low phosphate buffer (TLP) medium. The average mercury concentration in soil was 1,086 ± 3,096 mg/kg. The amount of rhizosphere bacteria found ranged from 1.2 X 105 ± 9.1 X 107 CFU/ g of roots. The isolates identified as Bacillus cereus strain ML259; Bacillus mycoides O-1 and Bacillus cereus strain LB1016, showed in vitro tolerance up to 700 and 900 mg/mL of HgCl2. The predominant plant species found in the soil corresponded to Bothriochloa pertusa (L.) A. Camus, accumulating mercury in concentrations of 1,086 ± 3,096 mg/kg in the rhizosphere. This plant species becomes a mercury indicator and accumulator plant and a possible alternative to remediate mercury-contaminated soils using the bioremediation technique assisted by rhizosphere bacteria for the management of soils contaminated with this metal.