Girguis Laboratory @ Harvard University

Thermal tolerance of hydrothermal vent palm worms

Deep-sea hydrothermal vent are one of the most physically and chemically taxing environments on the planet. Temperatures range from 2°C to well over 300°C around vent sulfides (or chimneys). Heavy metals, reduced sulfur compounds, and radioactive elements are released from the superheated and acidic effluent, while pressures typically exceed 250 atmospheres. Still, many organisms flourish in this environment, and some push the known physiological limits of animal life. Paralvinella sulfincola (Desbruyères and Laubier 1993), a vent endemic polychaete worm with unrivaled thermotolerance, is one such organism.

Paralvinella sulincola, shown here, is among the most thermotolerant of metazoans.

We have recently shown that Paralvinella sulfincola is among the most thermotolerant of organisms (Girguis and Lee 2006), living in habitats where temperatures vary rapidly from 2 °C to over 100°C (Sarrazin et al 1998). Recently we developed a high-pressure aquarium to study P. sulfincola thermal tolerance, and found them to be thermotaxic and extremely thermotolerant, with individuals surviving seven hours at 50° C (Girguis and Lee 2006). To date, no poikilothmeric animal (metazoan) has endured more than 15 minutes of exposure to such temperatures.

Thermotolerance has been studied in laboratory organisms at the molecular level for some time, however our understanding of what limits all animals to a narrow thermal regime (when compared to prokaryotes) is limited. As the only extremely thermotolerant organism capable of being maintained in the laboratory, P. sulfincola affords an unprecedented opportunity to study the physiological and biochemical adaptations (via transcriptomic and proteomic analyses) to extreme thermal milieus during well-controlled experiments.

Ecology and thermal tolerance of sulfide-hosted microbial communities

The sulfide incubator enables us to study the growth of microbes in situ, and to better understand their ecology and physiology.

The sulfide incubator enables us to study the growth of microbes in situ, and to better understand their ecology and physiology.

Hydrothermal vent sulfides are site of the sharpest thermal gradients in our biosphere. Temperatures vary from near freezing to over 350 degrees Celsius over a few centimeters. To date, our knowledge of such systems come from detailed analyses of microbial communities from recovered sulfides (Schrenk et al). The activity and ecology of these communities, however, remains largely unexplored.

In collaboration with Deborah Kelley at the University of Washington, we designed and developed an in-situ sensor/incubator package to quantify the spatial and temporal variation of environmental parameters and associated microbial communities within and on submarine hydrothermal edifices. The ultimate goals of this project are to determine under in-situ conditions the upper temperature limit of life, as well as the environmental parameters that support growth under these conditions. Questions to be addressed include: What thermal gradients are present within the walls of mature, diffusely venting edifices? What is the maximum growth and survival temperature of natural communities and of representative isolated cultures of hyperthermophiles within active vents?