A study of manganese-oxidizing microorganisms isolated from microbiocenoses of highly magnetic soils

Abstract

From the stand point of the possible use of microorganisms in water purification biotechnologies, studying microorganisms capable of removing dangerous pollutants such as heavy metals from the aquatic environment is of great importance. Microbial screening was conducted on isolates from microbiocenoses of highly magnetic soils of the city Mednogorsk (Orenburg region, Russia), to assess their resistance to manganese (II) ions. The objects of this research were nine strains of manganese-oxidizing microorganisms and two strains of iron-oxidizing microorganisms: Bacillus megaterium 69.3 and B. megaterium 69.5. It was observed that, most of the studied microorganisms were characterized by increased resistance to manganese (II) ions when grown on an agar medium. Maximum resistance to Mn (II) was observed in microbial strains: 55.2 and B. megaterium 69.5. The maximum tolerant concentration (MTC) of Mn (II) for these microorganisms was 300 and 350 mmol/L; the minimum inhibitory concentration (MIC) was 350 and 450 mmol/L, respectively. When studying the growth of the two microbial strains: 55.2 and B. megaterium 69.5 in liquid media for 5 days. It was discovered that, when cultured in a selective medium, microbial resistance of the strains to Mn (II) was higher compared to when cultured in a nutrient LB medium. The results showed high resistance of microorganisms to a range of Mn (II) concentrations: from 0,5 to 250 mmol/L in a liquid medium. Maximum growth of the studied microbial strains was observed at Mn (II) concentration of 10 mmol/L. These microbial strains with high resistance to Mn (II) open up the prospect of their practical use for biotechnological purposes involving the purification of drinking and wastewater from high manganese content.