Impact of Photooxidation and Biodegradation on the Fate of Oil Spilled During the Deepwater Horizon Incident: Advanced Stages of Weathering.

While the biogeochemical forces influencing the weathering of spilled oil have been investigated for decades, the environmental fate and effects of "oxyhydrocarbons" in sand patties deposited on beaches are not well-known. We collected sand patties deposited in the swash zone on Gulf of Mexico beaches following the Deepwater Horizon oil spill. When sand patties were exposed to simulated sunlight, a larger concentration of dissolved organic carbon was leached into seawater than the corresponding dark controls. This result was consistent with the general ease of movement of seawater through the sand patties as shown with a 35SO42- radiotracer. Ultrahigh-resolution mass spectrometry, as well as optical measurements revealed that the chemical composition of dissolved organic matter (DOM) leached from the sand patties under dark and irradiated conditions were substantially different, but neither had a significant inhibitory influence on the endogenous rate of aerobic or anaerobic microbial respiratory activity. Rather, the dissolved organic photooxidation products stimulated significantly more microbial O2 consumption (113 ± 4 µM) than either the dark (78 ± 2 µM) controls or the endogenous (38 µM ± 4) forms of DOM. The changes in the DOM quality and quantity were consistent with biodegradation as an explanation for the differences. These results confirm that sand patties undergo a gradual dissolution of DOM in both the dark and in the light, but photooxidation accelerates the production of water-soluble polar organic compounds that are relatively more amenable to aerobic biodegradation. As such, these processes represent previously unrecognized advanced weathering stages that are important in the ultimate transformation of spilled crude oil.

Youngiibacter fragilis gen. nov., sp. nov., isolated from natural gas production-water and reclassification of Acetivibrio multivorans as Youngiibacter multivorans comb. nov.

A taxonomic study employing a polyphasic approach was performed on a novel anaerobic bacterium isolated from natural gas production-water. The bacterium stained Gram-negative and consisted of non-motile, non-spore-forming, rod-shaped cells. Products of glucose or starch fermentation were ethanol, CO2, formate, acetate and H2. The predominant fatty acids were C16 : 0 ALDE and summed feature 3 comprising C16 : 1ω7c and/or C16 : 1ω6c. The DNA G+C content was 45.5 mol%. 16S rRNA gene sequence analysis demonstrated that the nearest phylogenetic neighbours of the novel strain were Acetivibrio multivorans DSM 6139(T) (98.5 %) and Proteiniclasticum ruminis JCM 14817(T) (95.4 %). The DNA-DNA hybridization value between the novel organism and Acetivibrio multivorans PeC1 DSM 6139(T) was determined to be only 30.2 %, demonstrating the separateness of the two species. Based on phylogenetic, phenotypic and chemotaxonomic evidence that clearly distinguished strain 232.1(T) from Proteiniclasticum ruminis and other close relatives, it is proposed that the novel isolate be classified as representing a novel species of a new genus within the family Clostridiaceae, Youngiibacter fragilis gen. nov., sp. nov. The type strain of the type species is 232.1(T) ( = ATCC BAA-2257(T) = DSM 24749(T)). In addition, Acetivibrio multivorans is proposed to be reclassified as Youngiibacter multivorans comb. nov.

Metabolic Capability of a Predominant Halanaerobium sp. in Hydraulically Fractured Gas Wells and Its Implication in Pipeline Corrosion.

Microbial activity associated with produced water from hydraulic fracturing operations can lead to gas souring and corrosion of carbon-steel equipment. We examined the microbial ecology of produced water and the prospective role of the prevalent microorganisms in corrosion in a gas production field in the Barnett Shale. The microbial community was mainly composed of halophilic, sulfidogenic bacteria within the order Halanaerobiales, which reflected the geochemical conditions of highly saline water containing sulfur species (S2O3 (2-), SO4 (2-), and HS(-)). A predominant, halophilic bacterium (strain DL-01) was subsequently isolated and identified as belonging to the genus Halanaerobium. The isolate could degrade guar gum, a polysaccharide polymer used in fracture fluids, to produce acetate and sulfide in a 10% NaCl medium at 37°C when thiosulfate was available. To mitigate potential deleterious effects of sulfide and acetate, a quaternary ammonium compound was found to be an efficient biocide in inhibiting the growth and metabolic activity of strain DL-01 relative to glutaraldehyde and tetrakis (hydroxymethyl) phosphonium sulfate. Collectively, our findings suggest that predominant halophiles associated with unconventional shale gas extraction could proliferate and produce sulfide and acetate from the metabolism of polysaccharides used in hydraulic fracturing fluids. These metabolic products might be returned to the surface and transported in pipelines to cause pitting corrosion in downstream infrastructure.

Rapid, colorimetric quantification of lipid from algal cultures.

Algae have significant potential as a source of biomass for the production of biofuels, due to their high growth rates and high cellular lipid content. Studies that address the use of algae as biofuels often require the frequent measurement of algal lipid content. Traditional methods for the quantification of lipid are, however, costly if sub-contracted, or involve the use of expensive analytical equipment that is not available in many labs. This study describes a simple, colorimetric method for the quantification of algal lipid from small amounts of culture. The technique is derived from a method for the quantification of fatty acids dissolved in chloroform. Algal lipids are saponified to fatty acids and then mixed with a copper reagent. Chloroform-extractable copper soaps of long-chain fatty acids are then colorimetrically measured by the addition of diethyldithiocarbamate to develop a yellow colored product. Linear responses for fatty acids in the range of C10:0 to C16:0 were observed for a concentration range between 0.025 and 1 micromol of fatty acid per 200 microL of sample. Fatty acids with chain lengths of less than twelve carbons produced significantly reduced signal. Decenoic acid yielded a slightly, but significantly lower signal than decanoic acid indicating that the assay underestimates the presence of unsaturated fatty acids. Lipid contents of Phaeodactylum tricornutum and Chlorella vulgaris CM2 were monitored for eight days during exponential growth to demonstrate the feasibility of the technique as a monitoring methodology. Overall, the method allowed reliable detection and quantification of fatty acid content from 1 to 2 mL of algal culture. Adaptation of the technique to micro-centrifuge format allows assaying 30 samples in less than 2h. Considering reagents and time, the total cost per assay was estimated at less than $5, representing a significant cost savings over traditional lipid quantification procedures.