Professor, Biological Oceanography and Astrobiology
University of Washington

Presentation Title: Arctic Winter Sea Ice: A Biological Museum or Evolutionary Playground?

During winter, the sea ice cover in the high Arctic grows and thickens, entrapping small organisms into its interior pore spaces. As temperatures drop, these spaces shrink in size as more pure water freezes, leaving behind high concentrations of sea salts that depress the freezing point and keep the sea-ice pores filled with liquid. Only single-celled microorganisms remain in this micrometer scale subzero salty habitat. There they are free of all grazers -- except viruses. Under conditions of environmental stress, viruses often fail to kill their hosts upon infection, instead incorporating as new DNA into their hosts' genomes. In the process, they can bring new genes from former hosts into the DNA of their new hosts. This striking form of horizontal gene transfer can be an adaptive boon for the microbes. The thick sea ice in the darkness of Arctic winter that has long appeared to Arctic explorers as a frozen museum for any life entrapped within it may in fact be an evolutionary playground where microbes and viruses interact in positive ways to bring new adaptations into the realm of oceanic microbes. Given the astronomical numbers of microbes that are trapped in the polar ice cap each year, returning to the ocean when the ice melts in summer, this form of evolution may contribute substantially to the ability of microbes to run the major biogeochemical cycles of the ocean.

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Research Interests

My research interests concern the limits of microbial life on Earth and enzyme-based strategies that allow microbes to push the limits as we perceive them. My formative research years were with NASA at the Goddard Space Flight Center, where I worked with "leftover" Viking mission technology to develop enzyme-based microbial detection assays. Graduate-level research (at the University of Maryland in College Park, PhD in 1981) then led me to examine effects of the hydrostatic pressures that characterize the cold deep ocean on microbial metabolism and growth. That work included isolation of novel pressure-requiring bacteria for which we eventually established a new genus, Colwellia, named after my advisor, Rita Colwell. Today, my students work with Colwellia psychrerythraea strain 34H, whose whole genome has been sequenced, as our model cold-adapted bacterium. My postdoctoral and independent research in the 1980s considered the combined effects of elevated pressure and temperature, as a result of the then-recent discovery of hydrothermal vents and thermophilic organisms from them. An opportunistic trip to the Arctic Ocean in 1987 captured my imagination with regards to near-freezing seawater and the ice that forms from it, and launched a still-continuing focus on field research in the high Arctic. Although laboratory and modeling work, often addressing microbial enzymes and exopolymers, is certainly part of my group's research, I embrace the philosophy that examining microbial behavior in situ, with as little disruption to the natural habitat as possible and as much knowledge of the physical- chemical environment as possible, can change the way we think about the limits of microbial life and the ability to survive extreme conditions. Interdisciplinary collaboration has become a hallmark of much of the work from my group, thanks in large part to ice- geophysicist Hajo Eicken at the University of Alaska, Fairbanks, and to many Canadian and other international Arctic colleagues.

Evidence for an ocean under the ice cover of Europa today (and an ocean on Mars in the past) brought me into the UW Astrobiology Program and has caused me to focus almost all of my efforts on microbial life in the cold, especially in saline ice formations. Within Arctic winter sea ice, briny fluids remain liquid down to at least -35°C, providing a whole new perspective on the limits to microbial life found within those brines. Because the accessible surfaces of Mars and Europa are on average at very cold temperatures (-55°C and much below), I am challenged to understand Earth life under such deeply frozen conditions. At UW, we have an Extremophile Laboratory (in the School of Oceanography, run jointly with John Baross and thanks to an NSF-IGERT award) that allows for inventive experimentation under both Earthly and extraterrestrial extremes and temperature and pressure.

Recent Publications

Deming, J.W. 2002. Psychrophiles and Polar Regions. Current Opinion in Microbiology 5:301-309

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The Persistent Professor: Jody Deming Carves a Crucial Niche in Cold Seas. By David Gordon. NOAA Research

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Sea ice: a refuge for life in polar seas? Christopher Krembs and Jody Deming. Thorough background information on the conditions and life in sea ice.

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Resources for Teaching

Arctic Exploration

A description of a recent research expedition in the arctic with text, photo and video logs. Educational resources are grouped by grade level from 5-12. Read Dr. Deming’s description of arctic microbes in Novel Microorganisms from the Cold Deep Sea.

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Extremophiles! Life in Ice

Developed by Colleen Kellogg and Heather Snookal.
Students discuss adaptations of life in extreme environments, with a particular focus on life in the Arctic.  They will also examine sea ice as a habitable environment during a quick hands-on activity.

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