Assessment of the number of catabolic genes of oil-contaminated soils

In this work, laboratory modeling of three levels of oil contamination (60, 120 and 250 g kg–1) was carried out for three types of soil: eutric podzoluvisols, haplic greyzem, and haplic chernozems. It was found that the content of fraction of aliphatic and aromatic hydrocarbons decreased in the samples with low and medium levels of contamination within 120 days. Oil contamination of soil in all concentrations led to a decrease in the total number of bacteria in comparison with uncontaminated soil by 1.2–5.5 times. It was shown that the number of genes belonging to the alkI and GP-PAH groups was in line with the total number of bacteria and decreased after oil contamination. At the same time, the number of alkane-monooxygenase genes belonging to the alkII and alkIII groups, as well as the genes of the GN-PAH group, was higher in the oil-contaminated soils as compared to the uncontaminated ones. Statistical analysis of the results showed that the level of soil contamination is a significant factor for the dynamics of the number of genes belonging to the alkI, alkII, GN-PAH, GP-PAH groups, as well as the duration of the experiment for alkI, alkIII, GN-PAH, GP-PAH groups. Soil type is a significant factor for the dynamics of the number of bacteria and number of genes belonging to the alkIII and GP-PAH groups. For other groups of genes, the type of soil is not a significant factor.