Research Overview

Thermophile research in the McDermott laboratory involves two independent research thrusts. One involves the development of a program that seeks to examine, characterize, and understand microbial populations inhabiting geothermally heated soil environments. The discovery, isolation, and characterization of novel and diverse thermophiles is a central platform of this particular project. The second thrust focuses on microbe-arsenic interactions in geothermal environments. Here, we wish to extend our general understanding of microbial arsenic redox biochemistry and physiology, and whether these reactions, when coupled with other relevant aqueous and solid phase chemical signatures, can be used as biomarkers of present or past microbial activity.

Geothermal Soils:

In recent work, we have isolated a novel thermophile, Thermobaculum terrenum, that appears to be the only cultured and characterized representative of a clade (Botero et al. 2004), which was previously comprised entirely of environmental clones within the phylum Chloroflexi (formally the Green Non-Sulfur division). In addition, we have isolated and characterized a proposed novel species of Geobacillus (species name tepidamans) (Schaeffer et al, submitted). In other work, we have employed DNA- and RNA-based molecular techniques to study population shifts occurring in response to increased soil temperature resulting from expansion of underlying geothermal activity (Norris et al. 2002b).

Microbe-Arsenic Interactions.

Work in this thrust seeks to improve our understanding of how microbes interact with and transform arsenic. Initial studies were molecular-based examinations of the microbial communities in arsenite-oxidizing thermal springs (in collaboration with Bill Inskeep). Subsequent work with this spring has involved the cultivation and characterization of different Hydrogenobaculum isolates (Donahoe-Christiansen et al. 2004). These hydrogenobacula are also being studied for their contribution to sulfide and hydrogen oxidation in these springs. This work has provided training for one postdoc, one MS student, and three undergraduate interns.

Other microbe-arsenic interaction work has included a proteomics examination of Sulfolobus global responses to arsenic (Barry et al. In preparation). The goal of this particular study was to extend our knowledge base of microbe-arsenic interactions beyond its current state, which is largely confined to studies that focus on ars gene expression. Other arsenic work includes studies aimed at investigating the potential contribution of cyanidia to arsenic transformations in the Yellowstone thermal springs. These evolutionarily ancient eukaryotic algae are found throughout Yellowstone and often dominate microbial communities in low pH thermal springs, pools, and soils.