The study applied microbial molecular biological techniques to show that 2.5% to 3.0% (w/w) of diesel in the soil reduced the types and number of bacteria in the soil and destroyed the microbial communities responsible for the nitrogen cycle. In the meantime, the alkane degradation gene alkB and polycyclic aromatic hydrocarbons (PAHs) degradation gene nah evolved in the contaminated soil. We evaluated four different remediation procedures, in which the biostimulation-bioaugmentation joint process reached the highest degradation rate of diesel, 59.6 ± 0.25% in 27 days. Miseq sequencing and quantitative polymerase chain reaction (qPCR) showed that compared with uncontaminated soil, repaired soil provides abundant functional genes related to soil nitrogen cycle, and the most significant lifting effect on diesel degrading bacteria γ-proteobacteria. Quantitative analysis of degrading functional genes shows that degrading bacteria can be colonized in the soil. Gas chromatography-mass spectrometry (GC-MS) results show that the components remaining in the soil after diesel degradation are alcohol, lipids and a small amount of fatty amine compounds, which have very low toxicity to plants. In an on-site remediation experiment, the diesel content decreased from 2.7% ± 0.3 to 1.12% ± 0.1 after one month of treatment. The soil physical and chemical properties returned to normal levels, confirming the practicability of the biosimulation-bioaugmentation jointed remediation process.

This study selected 27 soil samples from four representative horizontally distributed onshore oilfields in China to explore the diversity of soil microbial communities and their carbon fixation capacity, with a focus on the potential interaction between pollution and carbon fixation under oil pollution stress. The analysis of the soil physicochemical properties and microbial community structures from these oilfield samples confirmed a clear biogeographic isolation effect, indicating spatial heterogeneity in the microbial communities. Additionally, the key factors influencing microbial community composition differed across regions. The dominant bacterial phyla of soil microorganisms under soil pollution stress were Proteobacteria, Actinobacteriota, Chloroflexi, Acidobacteriota, Firmicutes, Bacteroidota, and Gemmatimonadota. A correlation network analysis identified Immundisolibacter, Acinetobacter, Blastococcus, Truepera, and Kocuria as key players in the microbial network, with most showing positive correlations. The results of the KEGG database functional annotation showed that degradation and carbon fixation metabolic pathways coexist in soil samples and maintain a balanced relative abundance. These metabolic pathways highlight the functional diversity of microorganisms. Among them, prokaryotic and eukaryotic carbon fixation pathways, along with benzoate degradation pathways, are predominant. These findings establish a theoretical basis for further exploration of the synergistic mechanisms underlying pollution reduction and carbon sequestration by microorganisms in petroleum-contaminated soils.

Cadmium (Cd) has been widely used in industry applications, leading to water and soil contamination. This study investigated the potential ability of Pseudomonas nitroreducens (11830) to perform the biosorption of cadmium from aqueous solution and soil. The biosorption characteristics were described using equilibrium isotherm and kinetic studies. The Langmuir adsorption isotherm indicated a better fit with the experimental data (R² = 0.980), with a maximum capacity of 160.51 mg/g at 30 °C in an initial aqueous solution of 300 mg/L Cd²⁺. The experiments followed a pseudo-second-order kinetics model (R² > 0.99), especially at a low initial concentration. The biosorption mechanisms involved were determined through scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS) and protein analysis. The SEM and TEM figures showed that the morphology of cells changed before and after the adsorption of Cd, and the EDS confirmed that Cd was absorbed on the surface of the cell. The analysis of proteins indicated that the protein species increased after the stimulation of Cd, which further confirmed the biosorption mechanism. A pot experiment confirmed that 11830 could passivate the cadmium in soil and reduce its uptake and utilization by Houttuynia cordata Thunb (H. cordata). This work demonstrates the potential application of microorganisms in inhibiting the accumulation of Cd in crops.