SCREENING FOR HYDROCARBON-OXIDIZING MICROORGANISMS RESISTANT TO HEAVY METALS AND SODIUM CHLORIDE

Abstract

In the process of extraction of hydrocarbon raw materials, in addition to mechanical disturbance of the soil cover, it is chemically contaminated with hydrocarbons and heavy metals contained in oil and oilfield wastewater, mainly of sodium chloride composition. Combined pollution has a more pronounced adverse effect on plants and soil biocenosis than each pollutant alone and leads to a very rapid loss of soil fertility. The aim of this work was to screen for new strains of hydrocarbon-oxidizing microorganisms resistant to elevated concentrations of sodium chloride and heavy metals. Isolation of strains of microorganisms from samples of technogenically contaminated soils from the territory of the Republic of Bashkortostan was carried out by the method of enrichment cultures on a liquid mineral medium of Raymond with oil. The hydrocarbon-oxidizing activity of the isolates was determined by the degree of destruction of the aliphatic oil fraction by the gas chromatographic method after extraction with hexane. The resistance of strains to the presence of sodium chloride and heavy metals (Zn, Co, Cd, Cu, Pb, Ni) was established by their growth on meat-peptone agar with various concentrations of NaCl or salts of these metals. Of the 14 isolated strains, 6 were selected, most actively growing on a solid medium with oil. The highest abundance and the most significant hydrocarbon-oxidizing activity during cultivation in a liquid medium with oil was found in strain 22 (the degree of oil biodegradation was 93.0%). All microorganisms were halotolerant and grew at 5 and 7% sodium chloride in the medium, but cultures 11 and 41, which withstood a NaCl concentration of 10%, turned out to be the most resistant to salinity. Strains 33.1 and 33.2 had the highest resistance to the action of metals. Lead and zinc were the least toxic to microorganisms. The results obtained should be considered preliminary, and the isolates themselves need further research with a view to their possible application in ecobiotechnology.