Extreme Life Processes Laboratory

Mechanisms of geologically relevant redox reactions of archaea and bacteria

Shown above are a recent acidic hot springs isolate and Evan Hall and Emily Knouf at a sampling site in the Mojave desert

Our interests in the microorganisms that inhabit a wide range of geologic features (including hydrothermal vents, acidic hot springs and aquatic and marine sediments) are focused on the systems that these organisms use to transfer electrons.  These reactions serve a variety of functions; they can provide the driving force for the life of the organism, be used to maintain an internal "balance" of oxidizing and reducing compound in the organism, or to protect against oxidative and other stresses.  Many geologically important reactions are controlled by this biochemistry, and we are specifically interested in the role that microbes play in the sulfur cycle and in the formation and breakdown of sulfur-containing minerals. 

Some organisms we are interested in:

Sulfolobus is a genus of acidophilic thermophiles that inhabit hot springs.  We are interested in the ways that these aerobes deal with oxidative stress, especially the roles of the coenzyme A thiol and the enzyme coenzyme A disulfide reductase.

Microorganisms from the genus Pyrococcus inhabit the anaerobic zones of hydrothermal vent systems and grow in the regions where the temperature is between 80 and 100 ºC.  Because they inhabit a unique environment and are not able to synthesize heme, these organisms have evolved a group of unique enzymes and small molecules to use in their redox reactions. Several projects are involved in characterizing these enzymes and small molecules.   In addition to the incredible heat,  the environment that Pyrococcus inhabits is full of an array of highly reactive and toxic compounds, including sulfides, arsenic and mercury, and current projects are looking at how these toxins might be utilized in thermophile redox metabolism.

Our studies with microbes from the genus Shewanella, which grows at "normal" temperatures and pHs, represent a real departure for the lab from studies involving conventionally defined extremophiles such as hyperthermophiles and acidpohiles.  In many ways, though, Shewanella's redox metabolism makes them more "extreme" than anything we've ever worked with - this is a microbe that is able to "breathe" metals and rocks!  We're looking at the ways that Shewanella can use sulfur for respiration, at both the molecular (mechanistic) and organismal level.

Current members of the lab include:

Karlo Lopez, HHMI Postdoctoral Fellow

Vinita Lukose ('08), Sneha Vakamudi ('08), David McCormick ('08), Kate Reid-Bayliss ('09), Lynn Sanford ('09), Diana Chen ('09), Grace Haung ('09), Angela Beckon ('09), Sanna Herwald ('10), and Lindsey Nam ('10)

Some recent articles from the lab:

1.  Boylan, J. A., Hummel, C., Benoit, S., Garcia-Lara, J., Treglown, J., Crane, E.J. III, and Gherardini, F.C.: Identification of a Coenzyme A Disulfide Reductase from Borrelia burgdorferi.  Molecular Microbiology, 59: 475-486 (2005).

2. Hummel, C.S., Lancaster, K.M., and Crane, E.J. III:  Determination of coenzyme A levels in Pyrococcus furiosus and other Archaea: implications for a general role for coenzyme A in thermophiles. FEMS Microbiological Letters,  252:229-34 (2005).

3.  Harris, D. R., Ward, D. E., Feasel, J. T., Lancaster, K.M., Murphy, R.D., Mallet, T.C. and Crane, E.J. III.: Discovery and characterization of a Coenzyme A disulfide reductase from Pyrococcus horikoshii:  Implications for the disulfide metabolism of anaerobic hyperthermophiles.  FEBS Journal 272:1189-1200 (2005).

4.  Ward, D., Donnelly, C., Mullendore, M., van der Oost, J., de Vos, W., and Crane, E.J. III.: The NADH oxidase from Pyrococcus furiosus: Implications for the protection of anaerobic hyperthermophiles against oxidative stress.  Eur. J. Biochem. 268: 5816-5823 (2001).

Lab members in spring 2007 - from left to right:  Emily Knouf, Caroline Small, E.J. Crane, Evan Hall, Charles Hummel (2006 alum), Vinita Lukose

Lab members in spring 2005 - from left to right:  Andrew Sandstrom, Courtney Davis, Ryan Murphy, Ganesh Devendra, John Vorhies, Krishnan Rangarajan, E.J. Crane, Kyle Lancaster, Charles Hummel, Kristl Dorschner, Evan Holdsworth

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