PAH degradation capability of forest soil microbial community

Polycyclic aromatic hydrocarbons (PAHs), mainly produced by uncompleted combustion, can accumulate and be retained in soils. Since PAHs have potentially toxic and carcinogenic effects, they represent a risk for human beings and ecosystems. Microbial degradation is the main responsible for PAH removal from soil. The objective of this research was to study the soil microbial activities and to reveal the microbial key-players involved in PAH degradation. Therefore, we applied a metaproteomic approach to link functional and taxonomic information of the soil microbial communities. Three different forest soils were chosen: holm-oak (H), beech (B) and black pine (P). In the laboratory, each soil was separately spiked with benzo[a]pyrene (95 mg/kg), pyrene and phenanthrene (125 mg/kg, each) and incubated in mesocosms, in controlled conditions, along 108 days, during which PAH quantification, hydrolytic, laccase and peroxidase activities and metaproteomics analyses were performed. At the end of the incubation, we observed in all forest soils a strong decrease in phenanthrene and pyrene content: phenanthrene reached a degradation percentage of 99, 95 and 58%, in H, B and P respectively; pyrene a degradation percentage of 97, 96 and 85%, in H, B and P respectively. Benzo[a]pyrene at the end of incubation showed a decrease of 1% in H, 5% in both B and P. Enzyme activity dynamics differed among soil forest systems, although similar trends were observed for the three mesocosms spiked with each PAH, in each soil type. Protein-based taxonomy was evaluated to analyze the microbial community composition, identifying some strains as key players in PAH degradation.