The determination of the stability of nitrogen-fixing microorganisms of the soil of Ecuador to toxic metals CrO42–, Ni2+, Cu2+

  • O. Yu. Bielikova
  • N. A. Matvieieva
  • L. S. Yastremskaya
  • A. B. Tashyrev
DOI: https://doi.org/10.7124/FEEO.v23.1026

Abstract

Aim. The aim of the work was to determine the stability of nitrogen-fixing microorganisms isolated from the rhizosphere of bromelia (Ecuador), to the effect of toxic metals. Methods. Microorganisms were isolated on the Ashby nutrient medium. The selected strains were cultured on a medium with Cu2+ (Cu (ІІ) citrate) from 50 to 500 mg/l by cation in steps of 50; Ni2+ (NiCl2) from 20 to 200 mg/l by cation in steps of 20; Cr (VI) (K2CrO4) from 20 to 100 mg/l with Cr (VI) in increments of 20. The growth of microorganisms in the presence of metals was characterized by the maximum permissible concentration (MPC) of metals, duration of lag phase and the number of colony-forming units (CFU) of nitrogen-fixing microorganisms with increasing concentration of toxic metals. Results. The selected dominant nitrogen-fixing microorganisms from the soil of Ecuador were resistant to toxic metals (Cu2+, Ni2+, Cr (VI)) in high concentrations. It was found that MPC for microbial communities of nitrogen-fixing microorganisms were: 40 mg/l Cr (VI), 300 mg/l Cu2+ and 100 mg/l Ni2+. Conclusions. It was shown that the selected dominant nitrogen-fixing microorganisms from the Ecuadorian soil were resistant to toxic metals (Cu2+, Ni2+, Cr (VI)) in high concentrations, which in 4–30 times exceed the damage or bactericidal concentrations for the majority of known organophosphate microorganisms of natural ecosystems.

Keywords: metalresistance, nitrogen-fixing microorganisms, Cu2+, Ni2+, Cr (VI).

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