Geomicrobiology Research @ Delaware


We are developing an integrated microbiological, biochemical, mineralogical and geochemical understanding of microbial oxidation of Fe, and more broadly, microbial interactions with minerals. Our goals are:

  1. 1. To understand the pathways of Fe during microbial oxidation.

  2. 2. To unravel the roles and evolution of Fe oxidizers over geologic time.

  3. 3. To determine the basic principles of how microbes interact with minerals, including relevant adaptations.

  4. 4. To discover new geomicrobial phenomena/mechanisms important to environmental processes.

Here is a UDaily article about our research.

Modern microbial Fe oxidation

Microbial Fe oxidation occurs in low oxygen, Fe-rich redox gradient environments, where abiotic oxidation rates are slow. We hypothesize that Fe-oxidizing microbes (FeOM) play important roles in these gradient environments where they fix carbon and precipitate reactive Fe minerals. We are identifying novel FeOM using a variety of culture methods, and developing cultivation-independent methods for detection and characterization of FeOM and their effects in the environment. These methods will enable us to more accurately characterize Fe cycling in modern environments. Toward this, our research addresses these questions:

  1. What is the diversity and ecology of FeOM?

  2. Where do we find FeOM?

  3. What are the genes involved in Fe oxidation?

  4. How are Fe biominerals distinctive in size, phase, morphology? What role do organics play in Fe biomineralization?

To investigate these questions, we are working on projects that cover a range of environments:

Photo descriptions and credits:

Left: SEM image of terrestrial iron microbial mat (C. Chan)

Top right: Clara at the cryo-TEM at LBL (Cristina Siegrist)

Bottom right: TEM image of FeS2 nanoparticle cluster (Yucel et al., 2011)

Bottom middle: Sampling deep sea iron microbial mat with “slurp gun” (JASON crew, WHOI)

If you use these images, please credit appropriately.

Time lapse phase contrast movie of Mariprofundus ferrooxydans producing a twisted Fe stalk. (Chan et al., 2011)

Biosignatures of Fe-oxidizing microbes

Fe-oxidizing microorganisms (FeOM) have likely been oxidizing, or “rusting” the Earth for billions of years, since the times of ferruginous oceans and pyrite sediments. Certain modern FeOM produce distinctive filamentous biominerals that could be promising biosignatures. In order to confidently identify and interpret FeOM biosignatures in the rock record, we are working with modern FeOM and putative microfossils to answer the following questions:

  1. What criteria can we use to distinguish biotic from abiotic Fe mineral precipitates?

  2. What environmental conditions do FeOM biosignatures indicate?

  3. When do microaerophilic Fe-oxidizing microbes first appear in the fossil record?

This is a collaboration with George Luther and David Emerson, as part of the NASA Exobiology program. Read more about the project in this abstract.

Microbe-S(0) interactions

  1. How do microbes make and consume elemental S(0)?

  2. We are working with a model S-oxidizing phototroph, Chlorobaculum tepidum, in collaboration with Tom Hanson, funded by the UDRF Strategic initiatives program and NSF (see abstract).

  3. We were just awarded a new NSF grant to work on cell-S(0) interactions involving chemolithotrophic S-oxidizers at the Frasassi Caves with Penn State collaborator Jenn Macalady. See pictures from our last field adventure on the photos page.

Deep sea hydrothermal vents at Loihi Seamount, Mid-Atlantic Ridge, Marianas – Here we are investigating linkages between ecology and structure of marine Fe microbial mats, in collaboration with D. Emerson and C. Moyer [abstract]. See our Loihi 2013 cruise blog.

Also see cruise sites for:

Fe microbial observatory (FeMO)

Mid-Atlantic Ridge 2012

Groundwater-surface water interfaces in streams and estuaries - We are investigating FeOM diversity and correlating their presence with hydrologic and geochemical parameters in upland and coastal aquifers at the Christina River Basin Critical Zone Observatory in collaboration with Holly Michael (NSF EPSCoR). We have cultured both known and novel FeOM from these sites, and will be using these strains to investigate mechanisms of Fe oxidation. Read about this NSF CAREER project here: abstract and article.

Aquifer undergoing bioremediation at the Rifle, CO DOE Integrated Field Research Challenge site, as part of the DOE Subsurface Biogeochemical Research program. We are isolating Fe-oxidizing microorganisms from biostimulation and remediation wells, and from the aquifer. We are using these isolates in lab and field experiments to investigate the influence of biomineralization on pore-scale permeability.