The biodegradation of organic pollutants is the main pathway for the natural dissipation and anthropogenic remediation of polycyclic aromatic hydrocarbons (PAHs) in the environment. However, in the saline soils, the PAH biodegradation could be influenced by soil salts through altering the structures of microbial communities and physiological metabolism of degradation bacteria. In the worldwide, soils from oilfields are commonly threated by both soil salinity and PAH contamination, while the influence mechanism of soil salinity on PAH biodegradation were still unclear, especially the shifts of degradation genes and soil enzyme activities. In order to explain the responses of soils and bacterial communities, analysis was conducted including soil properties, structures of bacterial community, PAH degradation genes and soil enzyme activities during a biodegradation process of PAHs in oilfield soils. The results showed that, though low soil salinity (1% NaCl, w/w) could slightly increase PAH degradation rate, the biodegradation in high salt condition (3% NaCl, w/w) were restrained significantly. The higher the soil salinity, the lower the bacterial community diversity, copy number of degradation gene and soil enzyme activity, which could be the reason for reductions of degradation rates in saline soils. Analysis of bacterial community structure showed that, the additions of NaCl increase the abundance of salt-tolerant and halophilic genera, especially in high salt treatments where the halophilic genera dominant, such as Acinetobacter and Halomonas. Picrust2 and redundancy analysis (RDA) both revealed suppression of PAH degradation genes by soil salts, which meant the decrease of degradation microbes and should be the primary cause of reduction of PAH removal. The soil enzyme activities could be indicators for microorganisms when they are facing adverse environmental conditions.

Background/Objectives: Petroleum contamination in soil exerts toxic effects on earthworms (Eisenia fetida) through non-polar narcotic mechanisms. However, the specific toxicities of individual petroleum components remain insufficiently understood. Methods: This study investigates the effects of four petroleum components—saturated hydrocarbons, aromatic hydrocarbons, resins, and asphaltenes—on earthworms in artificially contaminated soil, utilizing a combination of biochemical biomarker analysis and metabolomics to uncover the underlying molecular mechanisms. Results: The results revealed that aromatic hydrocarbons are the most toxic fraction, with EC50 concentrations significantly lower than those of other petroleum fractions. All tested fractions triggered notable metabolic disturbances and immune responses in earthworms after 7 days of exposure, as evidenced by significant changes in metabolite abundance within critical pathways such as arginine synthesis, a-linolenic acid metabolism, and the pentose phosphate pathway. According to the KEGG pathway analysis, saturated hydrocarbon fractions induced marked changes in glycerophospholipid metabolism, and arginine and proline metabolism pathways, contributing to the stabilization of the protein structure and membrane integrity. Aromatic hydrocarbon fractions disrupted the arachidonic acid metabolic pathway, leading to increased myotube production and enhanced immune defense mechanisms. The TCA cycle and riboflavin metabolic pathway were significantly altered during exposure to the colloidal fraction, affecting energy production and cellular respiration. The asphaltene fraction significantly impacted glycolysis, accelerating energy cycling to meet stress-induced increases in energy demands. Conclusions: Aromatic hydrocarbons accounted for the highest level of toxicity among the four components in petroleum-contaminated soils. However, the contributions of other fractions to overall toxicity should not be ignored, as each fraction uniquely affects key metabolic pathways and biological functions. These findings emphasize the importance of monitoring metabolic perturbations caused by petroleum components in non-target organisms such as earthworms. They also reveal the specificity of the toxic metabolic effects of different petroleum components on earthworms.

Fusarium and verticillium wilt are the primary diseases affecting cotton plants, significantly reducing both the yield and quality of cotton. Paenibacillus spp. are crucial biocontrol strains for controlling plant diseases. In this study, Paenibacillus peoriae MHJL1, which could prevent the pathogenic fungi of fusarium and verticillium wilt and promote cotton growth, was isolated from the rhizosphere soil of cotton plants. Whole-genome analysis of strain MHJL1 identified 16 gene clusters for secondary metabolite synthesis, including fusaricidins with potent antifungal properties. By optimizing the fermentation process, the cell and spore numbers of MHJL1 were increased to 2.14 × 10⁸ CFU/mL and 8.66 × 10⁸ CFU/mL, respectively. Moreover, the antifungal ability of MHJL1 was also increased by 31.48%. In pot experiments conducted with healthy soil, the control rates for MHJL1 against fusarium and verticillium wilt were found to be 44.83% and 58.27%, respectively; in experiments using continuously cropped soil, the control rates were 55.22% against fusarium wilt and 48.46% against verticillium wilt. Our findings provide valuable insights for the biocontrol application and fermentation of P. peoriae MHJL1, while also contributing a new resource for the development of microbial agents.

(1) Background: Polycyclic aromatic hydrocarbons (PAHs) are important components of petroleum and pose a serious threat to the soil environment of oil production well sites. Therefore, scientific risk thresholds and ecological risk assessment methods must be established for PAHs in petroleum-contaminated soils. (2) Methods: In this study, based on the environmental DNA (eDNA) method, the soil bacterial community was considered as a receptor to assess the ecological risks of PAH contamination in aged petroleum-polluted soils. A combination of the risk quotient and the equivalent toxicity factor was used to assess the ecological risk of PAHs. (3) Results: A dose–response curve was plotted to determine the 50% effective concentration (EC₅₀) of the total equivalent toxicity for 16 PAHs (∑TEQ_BaP) in petroleum-contaminated soils. Following the plot of the species sensitivity distribution (SSD) curve, the hazardous concentration for protecting 95% species values (HC₅) of petroleum hydrocarbons (TPHs), electrical conductivity (EC), and total equivalent toxicity of PAHs were calculated to be 892.1 μs·cm⁻¹, 149.9 mg·kg⁻¹, and 0.2601 mg·kg⁻¹, respectively. The regression models of the distribution factor (DF) and aging factor (AF) were defined as DF = −1.132 SOM + 0.033PAHs + 9.968 and AF = 242.518 SOM + 1256.029 lgpH + 0.024 EC − 1415.447. Following calibrations of the DF and AF, the value of HC₅ was determined as 0.1956 mg·kg⁻¹, which could be considered the risk threshold of the total toxicity of PAHs. The calibrated toxicity data distribution was consistent with that of the normal cumulative probability distribution model. The results showed that 50% of the aged petroleum-contaminated soils showed high-risk levels of bacterial communities exposed to PAHs. (4) Conclusions: This study provides a reference for deriving the ecological risk threshold of soil pollutants and explores alternative methods for the ecological risk assessment of PAHs at specific sites.

Petroleum-contaminated terrestrial ecosystems require effective bioremediation strategies. In this study, genomic analysis revealed key biodegradation genes on the Acinetobacter calcoaceticus 21# chromosome: alkane hydroxylases (alkB, almA, LadA) and aromatic ortho-cleavage pathway genes (catABC). Phylogenetic and multiple sequence alignment analyses of the almA gene in strain 21# revealed the presence of signature motifs characteristic of Baeyer–Villiger monooxygenase. Functional annotation analysis demonstrated stronger phylogenetic affinity of this protein to previously characterized BVMOs than to hydroxylases. Therefore, it is suggested that the AlmA protein in 21# exhibits BVMO activity and participates in the subterminal oxidation pathway of alkane degradation. Wild-type 21# degraded both n-Octacosane (24.47%) and pyrene (34.03%). Engineered 21#-A3 showed significantly enhanced n-Octacosane degradation (28.68%). To validate AlmA function and assess impacts of exogenous gene integration, we expressed the almA gene from A. vivianii KJ-1 via pET-28a(+)-av-almA-BH vector. Enzymatic assays demonstrated no activity toward long-chain alkanes but high activity for 2-decanone (0.39 U/mg) and 2-dodecanone (0.37 U/mg). Metabolite analysis confirmed recombinant AlmA functions through subterminal oxidation. This study establishes a foundational framework for advancing the optimization of petroleum-degrading bacteria. To engineer more efficient hydrocarbon-degrading strains, future research should integrate meta-cleavage pathways to expand their substrate utilization range for polycyclic aromatic hydrocarbons.