In situ transformation of ethoxylate and glycol surfactants by shale-colonizing microorganisms during hydraulic fracturing

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The original paper in ISMEJ is here and was the product of an interdisciplinary collaboration between several universities, national laboratories, and industry.

Hydraulic fracturing and horizontal drilling technologies have been increasingly used over the last two decades for increasing hydrocarbon production from low permeability shale formations. In this process, millions of liters of fluid containing chemical additives are injected into the subsurface at high pressure to generate fracture networks for the trapped oil and gas to escape. 

Astoundingly, a low-diversity halotolerant microbial community colonizes and thrives in this deep terrestrial ecosystem, despite salt concentrations 5+ times that of seawater [1]. Halanaerobium spp. is a consistent, dominant player in the system, in part because it can ferment a wide variety of organic compounds, reduce sulfur species, and grow under high pressure and salinities [2–7]. Our research team affectionately calls Halanaerobium the “shale weed”, as dozens of strains have been cultivated from produced fluid samples collected across the U.S. despite differences in (bio)geochemistry, temperature, pressure, and engineered processes.


Figure 1. O-H-I-O during a visit to a hydraulically fractured natural-gas well. I'm in the middle, surrounded by fellow graduate students Anne Booker and Casey Saup. (Photo: Mike Wilkins, Colorado State University)

As a first year PhD student, my advisor (PJ Mouser) and I were interested in applying my chemistry undergraduate degree (B.S. from The Ohio State University (OSU)) to determine whether this “shale weed” was capable of transforming xenobiotic organic compounds used by oil and gas (O&G) industry. We focused on (poly)glycol structures, as they are widely used as crosslinkers, scale inhibitors, surfactants, and solvents in slickwater fracturing operations [8]. I will never forget that conference call during my first year of graduate school when our Duke University collaborators (G. Getzinger and P.L. Ferguson), who analyzed our Utica-Point Pleasant Formation samples on their unique ultrahigh resolution analytical instruments, explained how some glycol-containing compounds were decreasing while others were not. We knew then that something important was occurring, and we designed experiments to test if and how our Halanaerobium isolates could transform these industry-relevant (poly)glycols. To understand the fundamental mechanisms of the chemical biotransformations, we needed to employed a wide range of analytical and molecular tools and expertise, including: LTQ-Orbitrap/qTOF-MS, shotgun proteomics and metagenomics, and NMR metabolite analysis. The findings summarized in this paper show why Halanaerobium should never be underestimated in its ability to persist and dominate like a weed even in an engineered, highly saline environment!

The experiments summarized in this paper caused me to fall in love with microbiology. Today, I am a postdoctoral researcher in the Colleges of Public Health and Veterinary Preventative Medicine at OSU investigating aspects of the human and animal gut microbiome. I would not likely be here if this research hadn’t opened my eyes to the wonders and unpredictability of the microbial world. This publication would not have been possible without the contributions of our excellent collaborators and co-authors. I am immensely grateful to these fantastic researchers whose expertise spans geochemistry to proteomics, and approaches range from NMR to environmental chemistry. This research was supported by the National Science Foundation Dimensions of Biodiversity (award no. 1830742).


1. Cluff MA, Hartsock A, MacRae JD, Carter K, Mouser PJ. Temporal Changes in Microbial Ecology and Geochemistry in Produced Water from Hydraulically Fractured Marcellus Shale Gas Wells. Environ Sci Technol 2014; 48: 6508–6517.

2. Daly RA, Borton MA, Wilkins MJ, Hoyt DW, Kountz DJ, Wolfe RA, et al. Microbial metabolisms in a 2.5-km-deep ecosystem created by hydraulic fracturing in shales. Nature Microbiology 2016; 1: 16146.

3. Booker AE, Hoyt DW, Meulia T, Eder E, Nicora CD, Purvine SO, et al. Deep Subsurface Pressure Stimulates Metabolic Plasticity in Shale-Colonizing Halanaerobium. Appl Environ Microbiol 2019; AEM.00018-19.

4. Booker AE, Borton MA, Daly RA, Welch SA, Nicora CD, Hoyt DW, et al. Sulfide Generation by Dominant Halanaerobium Microorganisms in Hydraulically Fractured Shales. mSphere 2017; 2.

5. Borton MA, Hoyt DW, Roux S, Daly RA, Welch SA, Nicora CD, et al. Coupled laboratory and field investigations resolve microbial interactions that underpin persistence in hydraulically fractured shales. PNAS 2018; 115: E6585.

6. Liang R, Davidova IA, Marks CR, Stamps BW, Harriman BH, Stevenson BS, et al. Metabolic Capability of a Predominant Halanaerobium sp. in Hydraulically Fractured Gas Wells and Its Implication in Pipeline Corrosion. Frontiers in Microbiology 2016; 7: 988.

7. Lipus D, Vikram A, Ross D, Bain D, Gulliver D, Hammack R, et al. Predominance and Metabolic Potential of Halanaerobium in Produced Water from Hydraulically Fractured Marcellus Shale Wells. Appl Environ Microbiol 2017; AEM.02659-16.

8. Elsner M, Hoelzer K. Quantitative survey and structural classification of hydraulic fracturing chemicals reported in unconventional gas production. Environ Sci Technol 2016; 50: 3290–3314.

Go to the profile of Morgan Volker Evans

Morgan Volker Evans

Postdoctoral Researcher, The Ohio State University

Postdoctoral researcher at The Ohio State University in the College of Public Health and Department of Veterinary Preventative Medicine. I'm interested in chemical-microbe interactions in microbiomes across environments- from oil & gas systems to the human or animal gut.

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