Water droplets in oil are microhabitats for microbial life

Meckenstock, Rainer U.; Netzer, Frederick von; Stumpp, Christine; Lueders, Tillmann; Himmelberg, Anne M.; Hertkorn, Norbert; Schmitt‐Kopplin, Philippe; Harir, Mourad; Hosein, Riad; Haque, Shirin; Schulze‐Makuch, Dirk

doi:10.1126/science.1252215

Cited by 121 publications

(103 citation statements)

References 31 publications

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“…Other ecosystems that contain comparable highly diverse HMW hydrocarbons are marine tar balls (61) and asphalt lakes (62). Although the chemical and physical aspects of HMW hydrocarbon degradation in marine tar balls have been well described and biodegradation is suspected, no microbial community compositions have been reported (61).…”

Section: Discussionmentioning

confidence: 99%

Roles of Thermophiles and Fungi in Bitumen Degradation in Mostly Cold Oil Sands Outcrops

Wong

Caffrey

et al. 2015

Appl Environ Microbiol

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Oil sands are surface exposed in river valley outcrops in northeastern Alberta, where flat slabs (tablets) of weathered, bitumensaturated sandstone can be retrieved from outcrop cliffs or from riverbeds. Although the average yearly surface temperature of this region is low (0.7°C), we found that the temperatures of the exposed surfaces of outcrop cliffs reached 55 to 60°C on sunny summer days, with daily maxima being 27 to 31°C. Analysis of the cooccurrence of taxa derived from pyrosequencing of 16S/18S rRNA genes indicated that an aerobic microbial network of fungi and hydrocarbon-, methane-, or acetate-oxidizing heterotrophic bacteria was present in all cliff tablets. Metagenomic analyses indicated an elevated presence of fungal cytochrome P450 monooxygenases in these samples. This network was distinct from the heterotrophic community found in riverbeds, which included fewer fungi. A subset of cliff tablets had a network of anaerobic and/or thermophilic taxa, including methanogens, Firmicutes, and Thermotogae, in the center. Long-term aerobic incubation of outcrop samples at 55°C gave a thermophilic microbial community. Analysis of residual bitumen with a Fourier transform ion cyclotron resonance mass spectrometer indicated that aerobic degradation proceeded at 55°C but not at 4°C. Little anaerobic degradation was observed. These results indicate that bitumen degradation on outcrop surfaces is a largely aerobic process with a minor anaerobic contribution and is catalyzed by a consortium of bacteria and fungi. Bitumen degradation is stimulated by periodic high temperatures on outcrop cliffs, which cause significant decreases in bitumen viscosity.T he world's largest oil sands deposit, located in western Canada, is contained in Lower Cretaceous sandstone formations in the Western Canadian Sedimentary Basin at depths of 0 to 800 m below the surface (mbs) (1, 2). Surface oil sands deposits are found in river valley outcrops (Fig. 1), where they are further changed by oxidative biodegradation and weathering.Oil sands hydrocarbon formed 84 million to 55 million years ago in tide-controlled river and estuarine sediment source rock, from where it migrated upwards and eastwards to accumulate at the northeastern margins of the basin centered around Fort McMurray, Alberta, Canada (2-4). The oil became severely biodegraded during this journey and following its placement at low depth and low temperature in the Athabasca, Cold Lake, and Peace River oil sands deposits that exist today. Biodegradation of low-molecular-weight components caused the oil to become more viscous, with the viscosity ranging from 1 cP for initially formed nondegraded light oil to 10 6 cP for heavily biodegraded, eastern Athabasca oil sands bitumen, which is currently in place (5-11). Bitumen is therefore depleted of low-molecular-weight aliphatic and aromatic hydrocarbons and enriched in polyaromatic hydrocarbons (PAHs), including alkylnaphthalenes or alkylphenanthrenes, as well as in naphthenic acids (NAs), resins, and asphaltenes (12)(13)(14). The ...

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Section: Discussionmentioning

confidence: 99%

Roles of Thermophiles and Fungi in Bitumen Degradation in Mostly Cold Oil Sands Outcrops

Wong

Caffrey

et al. 2015

Appl Environ Microbiol

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“…Lab-scale experiments have demonstrated discontinuous gas phase mobilization through a DNAPL pool, which generated significant concentrations of the gas compound above the pool [Mumford et al, 2010]. A recent study in a natural asphalt lake reported anaerobic microbes in miniscule water droplets entrapped in oil, providing field evidence for oil degrading apart from the bulk aqueous environment [Meckenstock et al, 2014]. Although the precise mechanism behind our direct outgassing formulation is not clear, its importance in simulations indicates that carbon losses to the gas phase significantly diminish the secondary water quality impacts of oil body degradation.…”

Section: 1002/2015wr016964mentioning

confidence: 99%

Reactive transport modeling of geochemical controls on secondary water quality impacts at a crude oil spill site near Bemidji, MN

Bekins

Cozzarelli

et al. 2015

Water Resources Research

129

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Anaerobic biodegradation of organic amendments and contaminants in aquifers can trigger secondary water quality impacts that impair groundwater resources. Reactive transport models help elucidate how diverse geochemical reactions control the spatiotemporal evolution of these impacts. Using extensive monitoring data from a crude oil spill site near Bemidji, Minnesota (USA), we implemented a comprehensive model that simulates secondary plumes of depleted dissolved O 2 and elevated concentrations of Mn 21 , Fe 21 , CH 4 , and Ca 21 over a two-dimensional cross section for 30 years following the spill. The model produces observed changes by representing multiple oil constituents and coupled carbonate and hydroxide chemistry. The model includes reactions with carbonates and Fe and Mn mineral phases, outgassing of CH 4 and CO 2 gas phases, and sorption of Fe, Mn, and H 1 . Model results demonstrate that most of the carbon loss from the oil (70%) occurs through direct outgassing from the oil source zone, greatly limiting the amount of CH 4 cycled down-gradient. The vast majority of reduced Fe is strongly attenuated on sediments, with most (91%) in the sorbed form in the model. Ferrous carbonates constitute a small fraction of the reduced Fe in simulations, but may be important for furthering the reduction of ferric oxides. The combined effect of concomitant redox reactions, sorption, and dissolved CO 2 inputs from source-zone degradation successfully reproduced observed pH. The model demonstrates that secondary water quality impacts may depend strongly on organic carbon properties, and impacts may decrease due to sorption and direct outgassing from the source zone.

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“…The understanding from this work provides valuable guidelines for producing surface nanodroplets with desired sizes by controlling the flow conditions. N anoscale droplets on a substrate (1) are an essential element for a wide range of applications, namely laboratory-on-chip devices, simple and highly efficient miniaturized reactors for concentrating products, high-throughput single-bacteria or singlebiomolecular analysis, encapsulation, and high-resolution imaging techniques, among others (2)(3)(4)(5). These droplets are of great interest also because they can have a payload and can flow internally in response to external flow.…”

mentioning

confidence: 99%

Formation of surface nanodroplets under controlled flow conditions

Zhang

Tan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

129

320

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Nanodroplets on a solid surface (i.e., surface nanodroplets) have practical implications for high-throughput chemical and biological analysis, lubrications, laboratory-on-chip devices, and near-field imaging techniques. Oil nanodroplets can be produced on a solidliquid interface in a simple step of solvent exchange in which a good solvent of oil is displaced by a poor solvent. In this work, we experimentally and theoretically investigate the formation of nanodroplets by the solvent exchange process under well-controlled flow conditions. We find significant effects from the flow rate and the flow geometry on the droplet size. We develop a theoretical framework to account for these effects. The main idea is that the droplet nuclei are exposed to an oil oversaturation pulse during the exchange process. The analysis shows that the volume of the nanodroplets increases with the Peclet number Pe of the flow as ∝ Pe 3=4 , which is in good agreement with our experimental results. In addition, at fixed flow rate and thus fixed Peclet number, larger and less homogeneously distributed droplets formed at less-narrow channels, due to convection effects originating from the density difference between the two solutions of the solvent exchange. The understanding from this work provides valuable guidelines for producing surface nanodroplets with desired sizes by controlling the flow conditions. N anoscale droplets on a substrate (1) are an essential element for a wide range of applications, namely laboratory-on-chip devices, simple and highly efficient miniaturized reactors for concentrating products, high-throughput single-bacteria or singlebiomolecular analysis, encapsulation, and high-resolution imaging techniques, among others (2-5). These droplets are of great interest also because they can have a payload and can flow internally in response to external flow. As a consequence, such droplets are widely exploited in formulation industries. Quite some effort has been devoted to produce a large amount of nanodroplets in a controlled way. The current techniques include trapping by microcavities, emulsion direct adsorption, microprinting, and others (6). The solvent exchange process is a simple and generic approach for producing droplets or bubbles at solid-liquid interfaces that are only several tens to hundreds of nanometers in height, or a few femtoliters in volume (7-11). The approach has attractive advantages, such as its capability of producing a large number of nanodroplets in one simple step, and its generality in chemical composition of the droplet liquid, and flexibility in aspect ratio of the droplets and spatial structure or size of the substrate (9, 12).For the formation of surface nanodroplets by solvent exchange, a hydrophobic substrate is exposed sequentially to two miscible solutions of oil, where the second solvent has a lower solubility of oil than the first. Such solubility difference leads to supersaturation of the liquid with oil during the solvent exchange and consequently to the nucleation of nanodroplets on...

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Water droplets in oil are microhabitats for microbial life

Cited by 121 publications

References 31 publications

Roles of Thermophiles and Fungi in Bitumen Degradation in Mostly Cold Oil Sands Outcrops

Roles of Thermophiles and Fungi in Bitumen Degradation in Mostly Cold Oil Sands Outcrops

Reactive transport modeling of geochemical controls on secondary water quality impacts at a crude oil spill site near Bemidji, MN

Formation of surface nanodroplets under controlled flow conditions

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