Formation and Functioning of Prokaryotic Complexes in Oil-Contaminated Soils with the Application of Biochar

The effect of biochar on the structure of the prokaryotic complex of microcosms in soils contaminated with oil products (podzol, soddy-podzolic, and gray forest soils) (Podzol, Retisol, and Phaeozem ) was studied using molecular biological methods (RT-PCR, metabarcoding) and fluorescent microscopy. The introduction of biochar (5% of soil mass) to soil samples containing oil products led to a significant increase (by an order of magnitude for podzol) in the biomass of prokaryotes compared to variants without it. With increased biomass, the diversity of the prokaryotic component after addition of biochar to soils polluted with oil products (a month after application) remains lower than in the control uncontaminated samples due to the emergence of certain hydrocarbon-oxidizing bacteria as dominants. For each of the studied soils, the most resistant to oil pollution genera of bacteria were determined: these were Pseudomonadota Massilia and Paraburkholderia in podzol, Ramlibacter solisilva and Masillia in soddy-podzolic soil, and Nocardioides, Gaiella, and Bacillus in the gray forest soil. In contaminated samples (both with and without addition of biochar) compared to the control, an increase in the content of functional genes responsible for the synthesis of catechol-2,3-dioxygenase (xylE) is observed, marking the initial stage of hydrocarbon degradation. When biochar is added to oil-contaminated soils, by day 30 of the experiment, the highest number of the xylE gene copies and the lowest content of residual petroleum products were noted. The obtained results on the abundance, biomass, taxonomic diversity, and biotechnological potential of the prokaryotic community of soils can help to develop effective strategies for bioremediation of oil-contaminated areas.