Moisture and Temperature as Factors of the Formation and Functioning of Prokaryotic Complexes in Oil-Contaminated Soils

The structure of prokaryotic complexes in microcosms of oil-contaminated and control soil samples (chernozem, Voronezh oblast, gray forest soil, Tula oblast, and chestnut soil, Volgograd oblast) was studied under conditions of different matric potentials of soil water and soil temperatures using molecular biology methods (RT-PCR, metabarcoding, FISH). An increase in the content of functional genes responsible for the synthesis of catechol-2,3-dioxygenase (xylE) and alkane monooxygenase (alkB) marking the initial stage of hydrocarbon degradation was observed in the studied oil-contaminated soils against the background of a decrease in the biomass and diversity of bacteria relative to the control. It was found that an increase in the matric potential of soil water from –800 to –0.1 kPa, simultaneously with an increase in the number of metabolically active representatives of bacteria and the number of alkB gene copies in the oil-contaminated soils incubated at 28°C corresponded to a decrease in the residual content of alkanes to 51%. The maximum content of the alkB gene was observed at the maximum water holding capacity and a medium incubation temperature (28°C). The highest number of copies of the xylE gene was found at medium values of the matric potential of soil water and temperature. The most resistant to oil pollution genera of bacteria were determined for every studied value of the matric potential of soil water and temperature. Representatives of Pseudomonadota became dominant under the conditions of low temperature and high water content, and spore-forming Actinomycetota and Bacillota became dominant at increased temperature and decreased water content. The obtained results on the abundance of metabolically active prokaryotic complex of soils and its taxonomic diversity and biotechnological potential can be useful for the development of efficient strategies for bioremediation of oil-contaminated areas.