The Prokaryotic Community Structure of Oil-Contaminated Chernozem during the Introduction of Nitrate and Potassium Chloride

Abstract

The effect of nitrate and potassium chloride salts, on the structure of the metabolically active prokaryotic community of oil-contaminated chernozem has been studied. Molecular biological approaches and bioinformatic methods of analysis were used in the study. The objects of the study were samples of chernozem selected in the Voronezh region (N 51°1′41″, E 40°43′31″). The phylogenetic and functional diversity of the prokaryotic complex of oil-contaminated chernozem was considered when introducing nitrate and potassium chloride under conditions of a slightly alkaline reaction of the medium. Contamination of chernozem with oil in an amount of 5% of the soil mass led to alkalinization of the medium from 7.1 to 7.9. The introduction of nitrate and potassium chloride, both separately and together in a total dose of 2 mmol/100 g of soil removed this negative effect. The combined addition of nitrate and potassium chloride led to a more than twofold increase in the biomass of metabolically active prokaryotic cells and the number of copies of functional genes responsible for the synthesis of alkanmonooxygenase enzymes involved in the decomposition of oil. In the presence of oil, the formation of a specific complex of bacteria was revealed, in which representatives of A-ctinobacteria (Rhodococcus erythropolis) and Alphaproteobacteria (Bradyrhizobium japonicum) prevailed. Rhodococcus erythropolis and Bradyrhizobium japonicum, being autochthonous organisms in uncontaminated soil, began to occupy dominant positions in oil-contaminated samples, and the introduction of nitrates enhanced this effect.