Effect of pyrene and phenanthrene in shaping bacterial communities in seagrass meadows sediments

Effects of pyrene on the structure and metabolic function of soil microbial communities

The widely detected pyrene (PYR) is prone to accumulate and pose risks to the soil ecosystem. In this study, an aerobic closed microcosm was constructed to assess the effects of PYR at the environmental concentration (12.09 mg kg^-1) on the structure, interactions, and metabolism of carbon sources of soil microbial communities. The results found that half-life of PYR was 37 d and its aerobic biodegradation was mainly implemented by both Gram-negative and Gram-positive bacteria as revealed by the quantitative results. High-throughput sequencing based on 16 S rRNA and ITS genes showed that PYR exposure interfered more significantly with the diversity and abundance of the bacterial community than that of the fungal community. For bacteria, rare species were sensitive to PYR, while Gemmatimonadota, Gaiellales, and Planococcaceae involved in organic pollutants detoxification and degradation were tolerant of PYR stress. Co-occurrence network analysis demonstrated that PYR enhanced the intraspecific cooperation within the bacterial community and altered the patterns of trophic interaction in the fungal community. Furthermore, the keystone taxa and their topological roles were altered, potentially inducing functionality changes. Function annotation suggested PYR inhibited the nitrogen fixation and ammonia oxidation processes but stimulated methylotrophy and methanol oxidation, especially on day 7. For the metabolism, microbial communities accelerated the metabolism of nitrogenous carbon sources (e.g. amine) to meet the physiological needs under PYR stress. This study clarifies the impacts of PYR on the structure, metabolism, and potential N and C cycling functions of soil microbial communities, deepening the knowledge of the environmental risks of PYR.