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Phenanthrene Degradation by Sphingobium sp. PM1B in Soil Containing Polyethylene Microplastics: Effects and Mechanisms
Summary
A year-long soil incubation experiment found that polyethylene microplastics increased the bioavailability of the polycyclic aromatic hydrocarbon phenanthrene, enhancing its biodegradation by Sphingobium bacteria by boosting water-soluble PHE content and favorable microbial community functions. This demonstrates that microplastics in soil act as vectors that alter the fate of co-pollutants like PAHs, compounding environmental and human health risks beyond the plastics themselves.
The coexistence of microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) represents an emerging source of combined pollution in the environment. Due to their strong hydrophobicity and large specific surface areas, MPs can interact with PAHs to change the environmental behaviors and biological effects of PAHs. However, PAH biodegradation in the presence of MP and the underlying mechanisms are unknown. In this study, polyethylene (PE) and phenanthrene (PHE) were selected as representative MP and PAH, respectively. A 1-year soil incubation experiment was carried out to explore the effects of PE on PHE biodegradation by Sphingobium sp. PM1B and the potential mechanisms based on modifications of soil chemical properties/microbial communities (i.e., diversity, composition, and function). The results showed that PE could increase the content of water-soluble PHE to improve the bioavailability of PHE, increasing PHE uptake and biodegradation by PM1B. PE may enhance PHE biodegradation by increasing the abundance of the PHE-degrading bacteria PM1B. PE also significantly enhanced the functions of chemoheterotrophy/aerobic chemoheterotrophy/aromatic compound degradation/sulfur respiration, aerobic/gram-positive phenotype, and metabolism, which might be favorable for the biodegradation of PHE. This study advances our understanding of the mechanisms of MP-influenced PAH biodegradation in soil.