Geomicrobiology Laboratory

Work in my laboratory centers around a unique property of some microbes to control the biological iron cycle. We have discovered several new groups of bacteria that are capable of capturing enough energy to grow by oxidizing Fe(II) (ferrous iron) to Fe(III) (ferric iron). These bacteria are adapted to growing at very low oxygen levels, which is important, because at higher O2 levels, the chemical oxidation of Fe(II) becomes so rapid it outcompetes biological oxidation. These Fe-oxidizing bacteria (FeOB) grow and are abundant in freshwater and brackish wetlands, water wells and distribution systems, hydrothermal vents in the ocean, and other marine environments where Fe(II) is present.

We have isolates of FeOB from the freshwater iron seeps, the rhizosphere, deep ocean hydrothermal vents, and coastal settings. Highlights of this work include pioneering efforts on the growth and isolation of novel Fe-oxidizing bacteria from both freshwater and marine environments. The discovery of the Zetaproteobacteria, a new class in the phylum Proteobacteria, that has a cosmopolitan distribution around the globe, but is restricted to marine environments with high concentrations of Fe(II). Furthermore, we have shown that marine and freshwater FeOB belong to very distinct lineages, sharing few genes in common, yet having very convergent lifestyles in terms of niche preference, physiology, as well as unique morphotypes. We have sequenced genomes from several pure cultures of FeOB, as well as over 30 single cell genomes that represent important environmental strains that cannot be grown in the laboratory.

This latter work has opened up new metabolic possibilities for FeOB, and allows more detailed study of their evolution allowing us to delve into the antiquity of these organisms that form unusual mineral structures that are recognized in the fossil record. We have shown FeOB may initiate biocorrosion of steel and could help structure a biocorrosion microbiome. We have made significant progress in identifying possible genes involved in neutrophilic iron oxidation, and this work is bringing us closer to understanding the mechanism of iron oxidation. Other recent discoveries include the finding that FeOB are abundant and the iron cycle is very active in tundra wetlands on the North Slope of Alaska, and the discovery of a 10 meter tall 'iron tower' associated with a hydrothermal vent site in the Pacfic Ocean. The work in my lab is funded through the National Science Foundation, NASA, and the Office of Naval Research. We have has significant sequencing support from the DOE's Joint Genome Institute.

Applied Research

The primary focus of my lab is on the basic science behind FeOB; however we are becoming increasingly interested in putting that knowledge to practice in solving myriad problems, primarily in the water industry, associated with FeOB, as well as developing novel beneficial applications for the reactive biogenic iron oxides these bacteria produce. I am on the Joint Task Force on 'Iron and Sulfur Bacteria/ for the 'Standard Methods for the Examination of Water and Wastewater'; I co-authored the forthcoming chapter on 'Iron-oxidizing Bacteria' for the American Water Works Association (AWWA) 'Manual of Water Supply Practices', and recently wrote a review article for AWWA Journal on FeOB. I also do consulting for industry.