Microbial interactions with magnetite enhance methane production from hydrocarbon biodegradation

Area of Science:

• Environmental microbiology
• Geochemistry
• Bioremediation

Background:

• Indigenous microbial communities in fine tailings (FT) biodegrade hydrocarbons and produce methane (CH4).
• Oil sands tailings ponds and end-pit lakes are significant sources of CH4 emissions.
• Understanding factors influencing microbial hydrocarbon metabolism is crucial for managing tailings.

Purpose of the Study:

• To investigate the effect of crystalline iron mineral magnetite on microbial hydrocarbon metabolism in FT.
• To assess magnetite's impact on methane production and hydrocarbon biodegradation rates.
• To explore the mechanism by which magnetite influences microbial activity.

Main Methods:

• Collected FT from methanogenically active and less active sites of an oil sands end-pit lake.
• Supplemented FT with magnetite and monitored hydrocarbon biodegradation and CH4 production.
• Analyzed mineral stability and microbial community composition.

Main Results:

• Magnetite addition significantly accelerated CH4 production and hydrocarbon biodegradation, particularly for recalcitrant aliphatics and monoaromatics.
• 86-92% of added magnetite remained stable, suggesting it facilitates mineralogical direct interspecies electron transfer (mDIET) rather than iron reduction.
• Magnetite supplementation enriched specific microbial taxa, including Coriobacteriaceae, Desulfosporosinus, and Syntrophus, potentially involved in mDIET.

Conclusions:

• Magnetite accelerates methanogenic biodegradation of hydrocarbons in FT, potentially increasing CH4 emissions.
• The findings suggest magnetite's role in enabling mDIET, a novel mechanism for enhancing anaerobic biodegradation.
• Magnetite shows potential for accelerating bioremediation of hydrocarbon-contaminated anaerobic environments.