Current (and recently finished) Research Projects.

Ecology and physiology of Fe-oxidizing bacteria (NASA/NSF)

Understanding the role that FeOB play in controlling rates of iron oxidation in natural systems and how they may influence the mineralogy of iron oxides.

Impact of Fe-oxidizing bacteria on biocorrosion of steel (ONR)

Understanding the role that marine Fe-oxidizing bacteria may play in corrosion of steel, either acting alone or in environmental consortia.

Evolution of the Zetaproteobacteria (NASA)

Discovery of this novel class of Proteobacteria associated with Fe-rich ecosystems has led us into studies about their evolution and the use of Fe(II) as an energy source

Development of a high resolution microbial mat sampler (NSF)

This is a collaborative project with scientists at the Woods Hole Oceanographic Institute to develop a new sampler for deep-sea microbial mats that can sample at sub-centimeter, and collect multiple independent samples.

Study of hydrothermal vent Fe-oxidizing microbial mat communities (NSF)

This is a collaborative project with colleagues at Western Washington University and the University of Delaware to investigate the functional and phylogenetic diversity of microbial iron mats at the Mid-Atlantic Ridge, Loihi Seamount, and the Mariana Forearc.

Investigation of microbial iron mats as biosignatures (NASA)

This is a collaborative project with colleagues at the University of Delaware to investigate how the textures of extant microbial iron mats and communities can be used to interpret ancient microbial fossils on Earth, and provide clues toward investigating the existence of such features on other planets.

Coastal marine iron cycling (NSF)

This is a collaborative project with colleagues at Harvard University aimed at understanding the role specific microbes may be playing in iron oxidation and cycling in coastal sediments, including establishing microcosms to study the process and microbial iron metabolism at extremely low oxygen concentrations.

Single cell transcriptomics (NASA)

The goal of this project is to develop techniques to follow gene expression in single bacterial cells using iron- oxidizing bacteria as a model system for studying these processes.

Importance of this work:

1. FeOB play both nuisance and beneficial roles in human activities; they are major agents of biofouling and biocorrosion in industrial and domestic water distribution systems; they can aid in the removal of iron and other harmful metals and organics in water treatment systems.
2. Iron oxides are very reactive minerals that have high sorption capacities for P, as well as Ar, Cd, Pb, U, and other metals. FeOB have a variety of ways of controlling the deposition of the Fe oxides that likely influence their reactivity. Many FeOB produce unique microstructures, commonly in the form of sheaths or stalks, composed of an organo-mineral matrix, that undoubtedly influences these interactions in unique ways.
3. FeOB may have influenced the biogeochemistry of the early Earth through precipitation of iron oxides and the formation of banded iron formations (the world’s primary source of iron ore).
4. Since iron is one of the most common elements in planetary composition, it is possible that iron-based metabolisms may have arisen on other planets, the study of extant FeOB on Earth can help us understand the types of habitats we should look for on other planets and what sort of biomarkers we might expect to find.
5. The biochemical mechanism of iron oxidation is perhaps the most poorly understand of any major biogeochemical process. The work here will help elucidate the mechanism of extracellular electron transfer associated with conservation of energy from iron oxidation.

Coastal Iron Cycling (NSF)

This project is focused on gaining a better understanding of the role bacteria play in cycling of iron in coastal sediments. Our supposition is that Fe-oxidation is an overlooked metabolism in many coastal sediments, and that marine Fe-oxidizing bacteria, especially the Zetaproteobacteria, could play an important role in this process.

Many sediments are rich in iron, often in the form of iron sulfides, and geochemists typically find significant concentrations of Fe(II) in pore-waters. Iron oxides themselves, an indicator of Fe-oxidizing activity, are generally not observed; however in areas of bioturbation, iron-oxide encrusted worm burrows can be common. Furthermore, it's possible there is a tight balance between oxidation and reduction of iron, so oxide deposition is rapidly depleted through reduction. One of our goals is to understand these processes to gain a better appreciation for the role of microbes in marine sedimentary iron cycling. This is important in terms of understanding the microbial ecology of sedimentary ecosystems, and because iron is an important micro-nutrient in the ocean that can often becoming limiting, thereby effecting primary productivity.

As processes like climate change alter the dynamics of marine ecosystems it is important to understand how linkages between microbial ecology and benthic ecology could ultimately impact planetary processes like primary production.

Another aspect of this project is to understand more about the physiology of Fe-oxidizing bacteria and how they can grow at very low oxygen levels. We believe this is their preferred habitat, but have little knowledge of the specific adaptations they have developed for this lifestyle. This is a collaborative project with Pete Girguis and Dave Johnston at Harvard.