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.