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:

Deep sea hydrothermal vents

Moderate - low temperature Fe-rich vents are the perfect spot for Fe-oxidizing microbes. We find these vents at seamounts and mic-ocean ridge  flanks. We recently revealed the intricate and beautiful architecture of these mats (see paper). We are currently investigating the metatranscriptomes, to determine how these mats function and respond to Fe(II).


    -NSF Biol. Oce. abstract

    -BCO-DMO data repository, including cruise info, reports

    -cruise sites: MAR, Loihi, Marianas

Groundwater-surfacewater interfaces and estuaries


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 NSF (see abstract).

  3. We are also investigating cell-S(0) interactions involving chemolithotrophic S-oxidizing Epsilonproteobacteria at the Frasassi Caves with Penn State collaborator Jenn Macalady (NSF abstract). See pictures from our 2011 field adventure on the photos page. 2016 pics coming soon!

On land, we find Fe-oxidizers in aquifers, especially where they intersect streams and oceans. These oxic/anoxic interfaces are biological hotspots where FeOM thrive and precipitate Fe oxides that can sequester carbon, phosphorous, and other metals.

We have isolated novel FeOB (Ferriphaselus sp.) and performed comparative genomics to uncover the genetic mechanisms of Fe oxidation and biomineralization.

We have also discovered new Fe-oxidizing habitats in a coastal aquifer and the seasonally-stratified Chesapeake Bay.

See NSF CAREER abstract.