Where are you from and what is your role in Extreme 2002?
I am on the scientific staff in the Biology Department of the Woods Hole Oceanographic Institution. During the Extreme 2002 cruise, our group (Stefan Sievert and myself) will be studying the microbiology and phylogeny of a novel marine bacterium that is able to form the waste product of its metabolism (sulfur) into a structure that allows it to be retained in hydrothermal vents. In addition, we will be implementing a newly developed device, the Autonomous Microbial Sampler (AMS), which will permit discrete samples to be taken at hydrothermal vents that are free from contaminating microbes and exogenous DNA. This device will be used to collect samples for our research as well as for others on the cruise.
What questions are you trying to answer and why?
We are studying an unusual microbe that oxidizes H2S in microaerobic environments and excretes its metabolic waste product, sulfur, in the form of long irregular filaments (~1-5 um x 500-1000 um). It can tolerate H2S (> 2 mM H2S) better than most sulfur-oxidizing bacteria and at high sulfide concentrations (which happens during eruptive events at hydrothermal vents) tends to form monocultures by excluding other competitors. The rigid filaments form an entangling matrix or mat that under the microscope has an appearance reminiscent of raw wool. This entangling matrix serves as a means for the organisms to be retained in high fluid-flow environments, like hydrothermal vents. The formation of mature sulfur filaments requires the participation of many members of the sulfur filament-producing microbial community. A proto-filament is excreted by a given organism and other members of the population radially attach along the axis of the filament and excrete little sulfur droplets at the site of their attachment, thickening the filament from ~0.2 m to 1-5 m. This is an unusual and interesting story — microbes as a community building their house out of metabolic waste for retention in their preferred chemical environment. The microbe has been identified to be in the genus Arcobacter, which we have seen in several locations now, including several hydrothermal vents and even coastal salt-marsh ecosystems.
The overall goal of the present project will be to extend ongoing studies of the microbial ecology of filamentous sulfur formation at hydrothermal vents. So far, little is known of the abundance, distribution, diversity, and function of the unusual Arcobacter organism in situ. Abundance and distribution will be assessed by Stefan Sievert in environmental samples by employing fluorescent in situ hybridization (FISH) with existing and newly developed fluorescently labeled oligonucleotides of different specificity targeting the 16S rRNA. Genomic DNA and RNA will be extracted from sulfidic hydrothermal environments for diversity analyses using denaturing gradient gel electrophoresis (DGGE), small-subunit rRNA gene cloning and sequencing. We will also be implementing H2S-enriched continuous flow reactors in simulation of warm water vents to obtain enrichment cultures of this organism for later study.
Why is this research important? What are the benefits?
The overall significance of this research lies in the characterization of the parameters and mechanisms by which this unique process of autotrophic sulfide oxidation occurs, as well as the abundance, distribution, and genotypic diversity of the responsible microbes in a number of different environments. Results will enhance our knowledge of the physiology and ecology of a novel, and heretofore-unconsidered, component of the sulfur cycle. Filamentous sulfur formation may be an important process at hydrothermal vents, extending into the shallow subsurface biosphere and driven by inorganic nutrients alone (i.e., H2S and CO2, N2).
What's your background and what lured you into marine science?
I grew up on a farm in the northeastern corner of Oregon, six miles north of a small town of 800 with the unlikely name of Athena. I guess I had a natural curiosity about how things worked from early on, judging from the stories my parents would later tell of how I would tear things apart and (usually) put them back together, just to see how they worked. The farm was a good place to grow up as one had to create one's own entertainment and interests, and there was equipment around that allowed you to build things from scratch. Many of the skills I learned on the farm I still use today in science.
Throughout my grade school and high school days, I possessed an interest and aptitude for science. The education taught in the small-town school was actually quite good, and it allowed a relatively smooth entry into college where I maintained a thrust in science, though I didn't know exactly in what area. An interest in biology and chemistry began to emerge in my early undergraduate experience. One summer I procured a job in a bacteriology lab at Portland State University. By the time the summer was over, I knew my future lay in the field of microbiology. I finished my undergraduate career and obtained a master's degree in microbiology at that university, where I focused on microbial biochemistry and enyzymology.
I then trekked eastward to the University of Illinois where I became interested in the unusual anaerobic microbes, the methanogens. These organisms were interesting in their ability to reduce carbon in its most oxidized from, CO2, to carbon in its most reduced form, CH4, a substantial metabolic feat. I focused on the enzymology and structural identification of the co-factor involved in the last step of methanogenesis. This was an intriguing project in that it required a mix of skills in microbiology, biochemistry, and analytical organic chemistry. My technical skills also became of use in the design and construction of specialized equipment used to complete my thesis work. I graduated with a Ph.D. in microbiology and moved farther east to the Woods Hole Oceanographic Institution (WHOI) to begin studies of the influence of high hydrostatic pressure on the growth and metabolism of deep-sea microbes. I have remained at WHOI and enjoy mixing technological development into my studies of marine microbiology. The AMS we will be implementing on this cruise is an example of where technological developments can enhance our ability to study remote environments.
