Metagenomic and Metatranscriptomic Responses of Chemical Dispersant Application during a Marine Dilbit Spill

The global increase in marine transportation of dilbit (diluted bitumen) can increase the risk of spills, and the application of chemical dispersants remains a common response practice in spill events. To reliably evaluate dispersant effects on dilbit biodegradation over time, we set large-scale (1,...

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Bibliographic Details
Published in:Applied and environmental microbiology 2022-03, Vol.88 (5), p.e0215121-e0215121
Main Authors: Cao, Yiqi, Zhang, Baiyu, Greer, Charles W, Lee, Kenneth, Cai, Qinhong, Song, Xing, Tremblay, Julien, Zhu, Zhiwen, Dong, Guihua, Chen, Bing
Format: Article
Language:English
Subjects:
Alteromonas
Aromatic compounds
Biodegradation
Biodegradation, Environmental
Biotransformation
Dispersants
Dispersion
Environmental Microbiology
Gene sequencing
Genomes
Marine transportation
Metagenome
Metagenomics
Microbial activity
Microcosms
Microorganisms
Nutrient concentrations
Oil spills
Petroleum - metabolism
Petroleum Pollution - analysis
RNA, Ribosomal, 16S - genetics
rRNA 16S
Seawater - chemistry
Stochasticity
Systems analysis
Water Pollutants, Chemical - analysis
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Summary:The global increase in marine transportation of dilbit (diluted bitumen) can increase the risk of spills, and the application of chemical dispersants remains a common response practice in spill events. To reliably evaluate dispersant effects on dilbit biodegradation over time, we set large-scale (1,500 mL) microcosms without nutrient addition using a low dilbit concentration (30 ppm). Shotgun metagenomics and metatranscriptomics were deployed to investigate microbial community responses to naturally and chemically dispersed dilbit. We found that the large-scale microcosms could produce more reproducible community trajectories than small-scale (250 mL) ones based on the 16S rRNA gene amplicon sequencing. In the early-stage large-scale microcosms, multiple genera were involved in the biodegradation of dilbit, while dispersant addition enriched primarily and competed for the utilization of dilbit, causing depressed degradation of aromatics. The metatranscriptomic-based metagenome-assembled genomes (MAG) further elucidated early-stage microbial antioxidation mechanism, which showed that dispersant addition triggered the increased expression of the antioxidation process genes of species. Differently, in the late stage, the microbial communities showed high diversity and richness and similar compositions and metabolic functions regardless of dispersant addition, indicating that the biotransformation of remaining compounds can occur within the post-oil communities. These findings can guide future microcosm studies and the application of chemical dispersants for responding to a marine dilbit spill. In this study, we employed microcosms to study the effects of marine dilbit spill and dispersant application on microbial community dynamics over time. We evaluated the impacts of microcosm scale and found that increasing the scale is beneficial for reducing community stochasticity, especially in the late stage of biodegradation. We observed that dispersant application suppressed aromatics biodegradation in the early stage (6 days), whereas exerting insignificant effects in the late stage (50 days), from both substance removal and metagenomic/metatranscriptomic perspectives. We further found that species are vital for the early-stage chemically dispersed oil biodegradation and clarified their degradation and antioxidation mechanisms. These findings help us to better understand microcosm studies and microbial roles for biodegrading dilbit and chemically dispersed dilbit
ISSN:0099-2240
1098-5336
DOI:10.1128/aem.02151-21