Our objective was to study the bacterial community changes that determine enhanced removal of petroleum hydrocarbons from soils subjected to bioaugmentation with the hydrocarbon-degrading strains Rhodococcus erythropolis CD 130, CD 167, and their combination. To achieve this, a high-throughput sequencing of the 16S rRNA gene was performed. The changes in the bacterial community composition were most apparent the day after bacterial inoculation. These changes represented an increase in the percentage abundance of Rhodococcus and Pseudomonas genera. Surprisingly, members of the Rhodococcus genus were not present after day 91. At the end of the experiment, the bacterial communities from the CD 130, CD 167, and control soils had a similar structure. Nevertheless, the composition of the bacteria in the CD 130 + CD 167 soil was still distinct from the control. Metagenomic predictions from the 16S rRNA gene sequences showed that the introduction of bacteria had a significant influence on the predicted pathways (metabolism of xenobiotics, lipids, terpenoids, polyketides, and amino acids) on day one. On day 182, differences in the abundance of functional pathways were also detected in the CD 130 and CD 130 + CD 167 soils. Additionally, we observed that on day one, in all bioaugmented soils, the alkH gene was mainly contributed by the Rhodococcus and Mycobacterium genera, whereas in non-treated soil, this gene was contributed only by the Mycobacterium genus. Interestingly, from day 91, the Mycobacterium genus was the main contributor for the tested genes in all studied soils. Our results showed that hydrocarbon depletion from the analyzed soils resulted from the activity of the autochthonous bacteria. However, these changes in the composition and function of the indigenous bacterial community occurred under the influence of the introduced bacteria.

The size and chemical composition of leachates migrating into the aquifer are dependent on the parameters of the waste and the storage conditions. Lysimeter studies allow us to determine the size and chemical composition of leachates as well as the leachate water balance. Lysimeter studies were conducted on a 230-L municipal waste sample for 6 months. During the tests, the specific electrolyte conductivity, pH, Eh, and temperature, as well as the chemical composition, microbiological analysis, and profiling of physiological population level using EcoPlate™ microarrays were measured in collected leachate samples. During the entire experiment, the amounts of inflow and outflow from lysimeters were measured. To assess the existence of significant differences in the chemical component concentrations in leachates, use of Principal Component Analysis was taken into account. The maximum EC value from leachate from the lysimeter was 33 mS/cm. High concentrations of ammonium ion (up to approx. 1400 mg dm −3), chlorides (up to approx. 6800 mg dm −3), and iron (up to approx. 31 mg dm −3) were observed in the effluents. The number of enterococci in May reached 53,000 cells/100 ml. By contrast, the number of these microorganisms was about 15,000 and 16,000 CFU/100 ml in January and April, respectively. Community-level physiological profiling indicates that the activity and functional diversity of microorganisms were higher in the leachate samples obtained in winter compared to effluents collected from lysimeters in spring.

No abstract