Hydrocarbon-Degrading Bacteria and the Bacterial Community Response in Gulf of Mexico Beach Sands Impacted by the Deepwater Horizon Oil Spill

TLDR

Oil from the Deepwater Horizon spill reached Gulf of Mexico shorelines, posing severe ecological and economic risks. The study aimed to identify dominant oil‑degrading taxa as model degraders or contamination indicators and to characterize how indigenous beach bacterial communities respond to oil contamination. Researchers sampled Pensacola Beach, FL, where weathered petroleum hydrocarbons (C₈–C₄₀) ranged from 3.1 to 4,500 mg kg⁻¹ in sands. Twenty‑four oil‑degrading strains from 14 genera—primarily Gammaproteobacteria such as *Alcanivorax* and *Marinobacter*—were isolated, and sequence data revealed a ~10‑fold rise in SSU rRNA gene abundance in oiled sands, with *Alcanivorax* dominating the community shift, demonstrating that oil contamination profoundly altered bacterial abundance and composition.

Abstract

ABSTRACT A significant portion of oil from the recent Deepwater Horizon (DH) oil spill in the Gulf of Mexico was transported to the shoreline, where it may have severe ecological and economic consequences. The objectives of this study were (i) to identify and characterize predominant oil-degrading taxa that may be used as model hydrocarbon degraders or as microbial indicators of contamination and (ii) to characterize the in situ response of indigenous bacterial communities to oil contamination in beach ecosystems. This study was conducted at municipal Pensacola Beach, FL, where chemical analysis revealed weathered oil petroleum hydrocarbon (C 8 to C 40 ) concentrations ranging from 3.1 to 4,500 mg kg −1 in beach sands. A total of 24 bacterial strains from 14 genera were isolated from oiled beach sands and confirmed as oil-degrading microorganisms. Isolated bacterial strains were primarily Gammaproteobacteria , including representatives of genera with known oil degraders ( Alcanivora x, Marinobacter , Pseudomonas , and Acinetobacter ). Sequence libraries generated from oiled sands revealed phylotypes that showed high sequence identity (up to 99%) to rRNA gene sequences from the oil-degrading bacterial isolates. The abundance of bacterial SSU rRNA gene sequences was ∼10-fold higher in oiled (0.44 × 10 7 to 10.2 × 10 7 copies g −1 ) versus clean (0.024 × 10 7 to 1.4 × 10 7 copies g −1 ) sand. Community analysis revealed a distinct response to oil contamination, and SSU rRNA gene abundance derived from the genus Alcanivorax showed the largest increase in relative abundance in contaminated samples. We conclude that oil contamination from the DH spill had a profound impact on the abundance and community composition of indigenous bacteria in Gulf beach sands, and our evidence points to members of the Gammaproteobacteria ( Alcanivorax , Marinobacter ) and Alphaproteobacteria ( Rhodobacteraceae ) as key players in oil degradation there.