Hydrocarbon degradation and response of seafloor sediment bacterial community in the northern Gulf of Mexico to light Louisiana sweet crude oil

• Published in: The ISME Journal Vol. 12; no. 10; pp. 2532 - 2543
• Main Authors: Bacosa, Hernando P., Erdner, Deana L., Rosenheim, Brad E., Shetty, Prateek, Seitz, Kiley W., Baker, Brett J., Liu, Zhanfei
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-10-2018; Nature Publishing Group
• Subjects: 45; 45/23; 631/326/2565/855; 631/326/41/2142; 704/172/169/896; Alkanes; Attenuation; Background levels; Bacteria; Biodegradation; Biodegradation, Environmental; Biomedical and Life Sciences; Communities; Crude oil; Deep sea; Deep sea environments; Dispersants; Ecology; Evolutionary Biology; Genes; Genomes; Geologic Sediments - microbiology; Gulf of Mexico; Hydrocarbon-degrading bacteria; Hydrocarbons; Life Sciences; Louisiana; Microbial activity; Microbial Ecology; Microbial Genetics and Genomics; Microbiology; Microflora; Microorganisms; Natural attenuation; Ocean floor; Oil spills; Organic chemistry; Petroleum - metabolism; Petroleum hydrocarbons; Petroleum Pollution - analysis; Polycyclic aromatic hydrocarbons; Proteobacteria - classification; Proteobacteria - metabolism; Sediment samplers; Sediments; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - metabolism; Louisiana; Gulf of Mexico
• ISSN: 1751-7362; 1751-7370
• DOI: 10.1038/s41396-018-0190-1

The Deepwater Horizon (DWH) blowout resulted in the deposition to the seafloor of up to 4.9% of 200 million gallons of oil released into the Gulf of Mexico. The petroleum hydrocarbon concentrations near the wellhead were high immediately after the spill, but returned to background levels a few years after the spill. Microbial communities in the seafloor are thought to be responsible for the degradation of hydrocarbons, however, our knowledge is primarily based upon gene diversity surveys and hydrocarbon concentration in field sediment samples. Here, we investigated the oil degradation potential and changes in bacterial community by amending seafloor sediment collected near the DWH site with crude oil and both oil and Corexit dispersant. Polycyclic aromatic hydrocarbons were rapidly degraded during the first 30 days of incubation, while alkanes were degraded more slowly. With the degradation of hydrocarbons, the relative abundances of
Colwelliaceae
,
Alteromonadaceae
,
Methylococales
,
Alcanivorax
,
Bacteriovorax
, and
Phaeobacter
increased remarkably. However, the abundances of oil-degrading bacteria changed with oil chemistry.
Colwelliaceae
decreased with increasing oil degradation, whereas
Alcanivorax
and
Methylococcales
increased considerably. We assembled seven genomes from the metagenome, including ones belonging to
Colwellia
,
Alteromonadaceae
,
Rhodobacteraceae
, the newly reported genus
Woeseia
, and candidate phylum NC10, all of which possess a repertoire of genes for hydrocarbon degradation. Moreover, genes related to hydrocarbon degradation were highly enriched in the oiled treatment, suggesting that the hydrocarbons were biodegraded, and that the indigenous microflora have a remarkable potential for the natural attenuation of spilled oil in the deep-sea surface sediment.