Anaerobic degradation of hexadecane and phenanthrene coupled to sulfate reduction by enriched consortia from northern Gulf of Mexico seafloor sediment

Abstract

To advance understanding of the fate of hydrocarbons released from the Deepwater Horizon oil spill and deposited in marine sediments, this study characterized the microbial populations capable of anaerobic hydrocarbon degradation coupled with sulfate reduction in non-seep sediments of the northern Gulf of Mexico. Anaerobic, sediment-free enrichment cultures were obtained with either hexadecane or phenanthrene as sole carbon source and sulfate as a terminal electron acceptor. Phylogenetic analysis revealed that enriched microbial populations differed by hydrocarbon substrate, with abundant SSU rRNA gene amplicon sequences from hexadecane cultures showing high sequence identity (up to 98%) to Desulfatibacillum alkenivorans (family Desulfobacteraceae), while phenanthrene-enriched populations were most closely related to Desulfatiglans spp. (up to 95% sequence identity; family Desulfarculaceae). Assuming complete oxidation to CO2, observed stoichiometric ratios closely resembled the theoretical ratios of 12.25:1 for hexadecane and 8.25:1 for phenanthrene degradation coupled to sulfate reduction. Phenanthrene carboxylic acid was detected in the phenanthrene-degrading enrichment cultures, providing evidence to indicate carboxylation as an activation mechanism for phenanthrene degradation. Metagenome-assembled genomes (MAGs) revealed that phenanthrene degradation is likely mediated by novel genera or families of sulfate-reducing bacteria along with their fermentative syntrophic partners, and candidate genes linked to the degradation of aromatic hydrocarbons were detected for future study.

Dispersant Enhances Hydrocarbon Degradation and Alters the Structure of Metabolically Active Microbial Communities in Shallow Seawater From the Northeastern Gulf of Mexico

“…Quantification of both SSU rRNA genes and dinitrogenase ( nifH ) genes was performed using quantitative PCR on a StepOnePlus real-time PCR platform (Applied Biosystems, CA, United States) using established methods (Gaby and Buckley, 2017; Kolton et al, 2019; Shin et al, 2019). The qPCR assay employed a PowerUp SYBR Green Master Mix (Applied Biosystems, CA, United States).…”

Chemical Profiling Provides Insights into the Metabolic Machinery of Hydrocarbon-Degrading Deep-Sea Microbes

“…Compared to other studies targeting specific metabolic intermediates of hydrocarbon degradation by microbes (8,45,46), the present study highlights the diverse chemical profile produced by deep-sea microbes when cultured with hydrocarbons. It is important to clarify that the metabolome analyzed could contain molecules derived from microbial cell walls.…”

Metagenomic Insights Into the Mechanisms for Biodegradation of Polycyclic Aromatic Hydrocarbons in the Oil Supply Chain

“…As hydrocarbon degradation has been demonstrated under aerobic and anaerobic conditions resulting in mitigation of contamination (Wiedemeier et al, 1999;Yu et al, 2005;Vasconcellos et al, 2010;Shin et al, 2019;Bianco et al, 2020), it is mandatory to improve our knowledge on microbial diversity in hydrocarbon-polluted environments, since the microbial composition and metabolic potential is one of limiting factors of the degradation fate of pollutants in contaminated sites (Lovley, 2003). Currently, the genetic basis of the catabolic pathways of the various PAHs remains poorly understood.…”