Victoria Orphan: Then and Now

WHAT DID THE 2010 EARLY CAREER AWARD ALLOW YOU TO DO?

Large reservoirs of methane lie buried beneath the seafloor, yet very little of this gas reaches the atmosphere because it is consumed by microbes. Scientists estimate up to 80% of the methane released from oceanic sediments worldwide is sequestered through a process known as anaerobic oxidation of methane. This process is catalyzed by a symbiotic partnership between methane-oxidizing archaea and sulfate-reducing bacteria. This partnership forms spatially structured, multi-celled aggregations. The archaea and bacteria metabolically cooperate to gain energy from oxidizing methane using seawater sulfate as the oxidant.

The identification and study of methane-consuming microorganisms and their partners is an important step towards understanding methane cycling and microbial influence on methane release. As with the majority of environmental microorganisms, this globally important microbial symbiosis has been difficult to culture and study in the laboratory. 

Support from my Early Career Research Award enabled me to develop and apply new culture-independent molecular and stable isotope-based methodologies to study microbial activities and cooperative interactions of methane-consuming microbes directly in environmental samples.

For example, Magneto-FISH is a process where microorganisms in the environment are fluorescently labeled based on their unique DNA sequence and subsequently captured using a magnet. It has provided new information about the extensive diversity of archaeal and bacterial partnerships existing in nature.

Further, applications of stable isotope labeling, combined with fluorescence microscopy and high-spatial resolution nanoscale secondary ion mass spectrometry (FISH-nanoSIMS), have resulted in new models that describe the process of anaerobic oxidation of methane, energy conservation mechanisms, and unique physiological traits among uncultured consortia of archaea and bacteria.

These multi-disciplinary methodological approaches are now being widely applied to diverse microbial communities and continue to provide valuable insights into the activities and ecology of uncultured microbes in nature.

ABOUT:

Victoria Orphan is the James Irvine Professor of Environmental Science and Geobiology in the Division of Geological and Planetary Sciences at the California Institute of Technology.

SUPPORTING THE DOE SC MISSION:

The Early Career Research Program provides financial support that is foundational to early career investigators, enabling them to define and direct independent research in areas important to DOE missions. The development of outstanding scientists and research leaders is of paramount importance to the Department of Energy Office of Science. By investing in the next generation of researchers, the Office of Science champions lifelong careers in discovery science.

For more information, please go to the Early Career Research Program.

THE 2010 PROJECT ABSTRACT:  

Integrative Molecular and Microanalytical Studies of Syntrophic Partnerships Linking C, S, and N Cycles in Anoxic Environments

The objective of this research is to improve understanding of anaerobic methane oxidation (a potent greenhouse gas) by microbes, a globally significant biogeochemical process. Anaerobic methane oxidation results in the consumption of methane in numerous anoxic environments and is thought to have global climate significance as a biogeochemical carbon cycle pathway.

This research will focus on a metabolic partnership between sulfate‐reducing bacteria and methane‐oxidizing archaea that allows metabolism of methane for energy under anoxic conditions. The work emphasizes the optimization of new technologies for visualization of interactions between the partner organisms at the level of single microbial cells and the tracking of joint metabolic processes.

RESOURCES:

Dekas, A.E., Chadwick, G.L., Bowles, M.W., Joye, S.B. and Orphan, V.J., “Spatial distribution of nitrogen fixation in methane seep sediment and the role of the ANME archaea.” Environmental Microbiology 16(10), 3012 (2014). [DOI: 10.1111/1462-2920.12247]

Green-Saxena, A., Dekas, A.E., Dalleska, N.F. and Orphan, V.J., “Nitrate-based niche differentiation by distinct sulfate-reducing bacteria involved in the anaerobic oxidation of methane.” The ISME Journal 8(1), 150 (2014). [DOI: 10.1038/ismej.2013.147]

McGlynn, S, G. Chadwick, C. Kempes, & V.J. Orphan, “Single cell activity reveals direct electron transfer in methanotrophic consortia.” Nature 526, 53 (2015). [DOI: https://www.nature.com/articles/nature15512]

Additional profiles of the 2010 Early Career Award winners can be found at: https://www.energy.gov/science/listings/early-career-program.

The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit www.energy.gov/science.