Metagenomic and metatranscriptomic responses of natural oil degrading bacteria in the presence of dispersants.

Oil biodegradation has been extensively studied in the wake of the deepwater horizon spill, but the application of dispersant to oil spills in marine environments remains controversial. Here, we report metagenomic (MG) and metatranscriptomic (MT) data mining from microcosm experiments investigating the oil degrading potential of Canadian west and east coasts to estimate the gene abundance and activity of oil degrading bacteria in the presence of dispersant. We found that the addition of dispersant to crude oil mainly favours the abundance of Thalassolituus in the summer and Oleispira in the winter, two key natural oil degrading bacteria. We found a high abundance of genes related not only to n-alkane and aromatics degradation but also associated with transporters, two-component systems, bacterial motility, secretion systems and bacterial chemotaxis.

Bioremediation (bioaugmentation/biostimulation) trials of oil polluted seawater: a mesocosm simulation study.

Bioaugmentation (amendment with selected bacterial strains) and/or biostimulation (nutrients addition and/or air supply) are relatively new fields in environmental microbiology for preventing pollution and cleanup contamination. In this study, the efficiency of application of bioaugmentation/biostimulation treatments, for recovery of crude oil-polluted seawater, was evaluated. Three different series of experiments were performed in a "Mesocosm Facility" (10.000 L). Natural seawater was artificially polluted with crude oil (1000 ppm) and was amended with inorganic nutrients (Mesocosm 1, M1), inorganic nutrient and an inoculum of Alcanivorax borkumensis SK2(T) (Mesocosm 2, M2) and inorganic nutrient and an inoculum of A. borkumensis SK2(T) and Thalassolituus oleivorans MIL-1(T) (Mesocosm 3, M3), respectively. During the experimental period (20 days) bacterial abundance (DAPI count), culturable heterotrophic bacteria (CFU count), MPN, microbial metabolic activity [Biochemical Oxygen Demand and enzymatic activity (leucine aminopeptidase LAP, ß-glucosidase BG, alkaline phosphatase AP)] and quali-, quantitative analysis of the composition of total extracted and resolved hydrocarbons and their derivates (TERHCs) were carried out. The microbiological and physiological analysis of marine microbial community found during the three different biostimulation and bioaugmentation assays performed in mesocosms show that the load of crude oil increases total microbial abundance, inhibits the activity of some enzymes such as LAP while stimulates both AP and BG activities. The biodegradation results show that bioaugmentation with A. borkumensis SK2(T) alone is able to produce the highest percentage of degradation (95%) in comparison with the biostimulation treatment (80%) and bioaugmentation using an Alcanivorax-Thalassolituus bacterial consortium (70%). This result highlights the reduced biodegradation capability of the consortium used in this study, suggesting an unfavourable interaction between the two bacterial genera.

Kinetic consequences of replacing the internucleotide phosphorus atoms in DNA with arsenic.

It was claimed in a recent publication that a strain of Halomonadacea bacteria (GFAJ-1) isolated from the arsenic-rich waters of Mono Lake, California is able to substitute arsenic for phosphorus in its macromolecules and small molecule metabolites. In this short Perspective, we consider chemical and biochemical issues surrounding the central claim that Halomonadacea GFAJ-1 is able to survive while incorporating kinetically labile arsenodiester linkages into the backbone of its DNA. Chemical precedents suggest that arsenodiester linkages in the putative arsenic-containing DNA of GFAJ-1 would undergo very rapid hydrolytic cleavage in water at 25 °C with an estimated half-life of 0.06 s. In contrast, the phosphodiester linkages of native DNA undergo spontaneous hydrolysis with a half-life of approximately 30,000,000 y at 25 °C. Overcoming such dramatic kinetic instability in its genetic material would present serious challenges to Halomonadacea GFAJ-1.

Deep-sea oil plume enriches indigenous oil-degrading bacteria.

The biological effects and expected fate of the vast amount of oil in the Gulf of Mexico from the Deepwater Horizon blowout are unknown owing to the depth and magnitude of this event. Here, we report that the dispersed hydrocarbon plume stimulated deep-sea indigenous γ-Proteobacteria that are closely related to known petroleum degraders. Hydrocarbon-degrading genes coincided with the concentration of various oil contaminants. Changes in hydrocarbon composition with distance from the source and incubation experiments with environmental isolates demonstrated faster-than-expected hydrocarbon biodegradation rates at 5°C. Based on these results, the potential exists for intrinsic bioremediation of the oil plume in the deep-water column without substantial oxygen drawdown.