How the smallest of microbes tolerate extreme marine conditions

Climate warming has the Arctic Sea ice cover receding and thinning, signaling changes in the environment for the marine megafauna at the top of the food chain and the microscopic algae and bacteria at the bottom of it. Living in sea ice and the waters and sediments below it, these microbes are responsible for fueling everything else in the ecosystem. Studying how changes to the sea ice cover will affect the base of the food chain is thus essential to predicting the future of ice-dependent ecosystems. Dr. Jody Deming, Walters Endowed Professor of Biological Oceanography at University of Washington, works to understand how the smallest of microbes, particularly the naturally occurring cold-adapted bacteria, have evolved to tolerate if not thrive under extreme marine conditions, including subzero temperature and high salt concentration as encountered inside sea ice but also high pressure experiences deeper into the ocean. Because bacteria adapted to live in the cold can also be expected to be "on the front line" of defense against an oil spill in the Arctic, Dr. Deming’s fundamental studies on the bacterial capacity to produce antifreeze agents and other compounds that function as natural oil dispersants can lead to real-world applications in the future.

The first group to determine how to use microscopy to peer into sea ice without melting it, Dr. Deming and her colleagues continue to incorporate novel microscopic techniques to observe microbial behavior under extreme conditions in the lab and to probe inside the unmelted ice in the field. Current projects involve the use of digital holographic microscopy to observe microbes swimming in the subzero brines that form a liquid network inside the ice cover: an excellent and unambiguous indicator that the organisms are not only alive but also active. Such observations are highly significant, given that high salt concentrations and freezing conditions have long been considered ways to stop bacterial activity. In the 1980s, Dr. Deming discovered a new bacterium living in the cold and very deep waters of the Caribbean, which led her to name an entire genus, genus Colwellia, after her former graduate advisor Dr. Rita Colwell. Members of the genus Colwellia are now known to occur throughout the cold deep Gulf of Mexico and the cold ice and waters of the Arctic Ocean and the Antarctic seas. For rigorous, robust research on how it is possible for life forms to exist under these extreme conditions, Dr. Deming and her team often travel into the Arctic in winter to acquire fresh samples and work with them immediately, in ship-based or readily accessed coastal labs, before the natural microbial communities can become altered. Ultimately, Dr. Deming believes that her basic research will contribute to the search for microbial life on other ice-covered planets and moons in our Solar System, while at home can lead to development of new antifreeze products, for example to preserve biomedical tissues or samples, or ways to ameliorate oil spills in polar regions where the oil may permeate or accumulate under the sea ice.

Current projects include:

  • Natural Antifreeze Products: Dr. Deming grows her model organism from the genus Colwellia under extreme conditions in the lab, to examine its ability to grow over a range of temperatures, from refrigerator to deep-freeze temperatures (it dies at room temperature). Dr. Deming and her students have found that as soon as the organism is exposed to temperatures that will cause its surroundings to freeze, it begins to release exopolymers, or sugary gelatinous materials that functions as antifreeze agents. Even though the microbe is being frozen into what looks like solid ice to us, it carries a personal coating of the sugary material that allows it to keep its immediate surroundings from crystallizing into ice and therefore to have a pool of liquid in which to live. Dr. Deming then takes her knowledge of the antifreeze process learned in the lab back into the field in the Arctic to work with natural sea ice, to test her theories on the natural production of antifreeze. The team has also been researching whether these antifreeze materials serve additional functions, for example, to buffer the microbes against the high salt concentrations of the sea ice brines they inhabit. Currently, her students are studying how these materials may change not only the physical structure of the ice, but also influence the rate at which it freezes and thaws. Since the Arctic Ocean harbors not a solid ice cover but ice with many interior pore spaces kept open by live microbes, Dr. Deming hopes to understand how the microbes living inside the ice may be weakening the ice, becoming in effect a biological “icebreaker.”
  • Oil Dispersants at Very Low Temperature: As various research teams began to study the oil plume that formed in the cold deep waters of the Gulf of Mexico during the BP oil spill, they discovered that some of the first responders to the oil were naturally-occurring bacteria from the genus Colwellia. Members of this genus, though well known to live in cold seawater, whether from the cold deep sea or polar environments, are not known to degrade or consume oil, making their growth in this cold oil plume a mystery. Dr. Deming has since discovered that her model Colwellia organism produces exopolymers that have the ability to disperse oil in the cold, especially under deep-sea pressure. She suspects that such exopolymers were produced by Colwellia in the deep oil plume and helped to disperse large oil droplets into much smaller ones that its bacterial neighbors, which were equipped to degrade the oil, could more easily feed upon. These neighbors, in breaking the oil down to very small compounds on which Colwellia could then feed, completed this proposed cycle of “microbial altruism.” Her team continues to explore this novel functioning of exopolymers produced in the cold under high pressure.
  • Motility: Instead of “sitting” inside the ice merely protecting themselves, what if cold-adapted bacteria were swimming from pore to pore and interacting with each other? To answer this basic question, Dr. Deming and her students work with her model organism in the lab, suspending it in different types of liquid solutions in varying degrees and mixtures of sugar and salt, and freezing it to colder and colder temperatures. Using an epifluorescent microscope in a freezer lab, they have determined when the microbes are swimming, and so far have seen swimming at temperatures down to –12’C. With a novel and robust digital holographic microscope that can be taken into the field, Dr. Deming and her colleagues have witnessed microbes swimming in their natural environment of sea ice brines. She hopes to push the boundaries of swimming conditions to even greater extremes than currently documented.
  • Implications for Exploring Life on Icy Planets and Moons Elsewhere: The digital holographic microscope that Dr. Deming incorporates into her lab and field research is unique in its ability to image the very smallest of living microorganisms and provide holograms of their swimming behavior. This laser-based microscope has no moving parts; it does not need manual adjustment of lenses and can withstand all kinds of harsh circumstances, making it suitable for deployment on a spacecraft as a life detection instrument. Currently, Dr. Deming joins a team of researchers at Caltech and NASA’s JPL in developing this microscope as a potentially great new tool for exploring what tiny life forms may be inhabiting other icy planets and moons, in particular Europa, the moon to Jupiter, with its ice-covered ocean that NASA missions will explore in future.

Bio

Dr. Jody Deming grew up in the “extreme environment” of southeast Texas, extremely hot and humid. She could have been in the first class of women to attend Texas A&M University, following in her father’s footsteps, an Aggie whose plan was interrupted to fight in WWII. However, her father died when she was 16, and her mother, brothers, and sisters were left without resources. Jody was recruited by Smith College, which she was able to attend through a combination of financial aid, a work-loan program, and a piano scholarship. She had never imagined pursuing a higher degree in science, having focused for many years on piano and language. However, she recalls that she was “always distracted by science,” and when finally forced to declare a major, chose to complete an undergraduate degree in biology.

Still not knowing what she wanted to do, she found employment as a research technician under contract to NASA following the Viking mission in 1974, in a lab that focused on developing bacterial detection methods. Here, she experienced the enormous satisfaction of being creative at the lab bench, while with piano, she too often felt as though she was merely interpreting the creativity of others. This early work taught her that she could contribute original research to the progress of scientific understanding of the world around us.

The tide was turned forever when Dr. Rita Colwell, a marine microbiologist and scientific administrator who went on to become the 11th Director of the United States National Science Foundation and science advisor to two US presidents, visited Dr. Deming’s supervisor at the Goddard Space Flight Center one day and came into the lab to meet and begin recruiting her to graduate school. Dr. Deming already had publications and patents by then, yet did not realize that she was operating at a higher level than the undergraduate degree she held at the time would suggest, and thus responded, “but I’m not good enough for graduate school.” When they met for a formal interview at Dr. Colwell’s lab, Dr. Deming saw that the lab was such an exciting place that she was hooked from the moment she entered -- and the rest is history.

Dr. Colwell had a deep-sea bacterial research program ongoing at the time and Dr. Deming embraced that field for her doctoral work. Detecting pressure-adapted bacteria in the deep ocean, at a time when none were known, was not unlike trying to detect microbial life elsewhere, on some other planet or moon. Dr. Deming was motivated by the mystery of it all, by the astonishing concept that some microbes somewhere had evolved to thrive or survive almost any conditions known. The ocean became her home base for exploring the limits of life on Earth, and to this day, Dr. Colwell teases her that she thought she “wasn’t good enough for graduate school.”

Outside of her research, Dr. Deming loves to solve puzzles, tend garden, and swim. She truly loves to swim, and is unfazed by Seattle’s “cold and salty water.”

For more information, visit http://www.ocean.washington.edu/people/faculty/deming/

Awards

Walters Endowed Professorship, 2009-present

College of the Environment

Honorary Doctorate, Science and Engineering, 2006

Université Laval, Quebec City, Canada

Elected, US National Academy of Sciences, 2003

Elected, American Academy of Microbiology, 1999

NSF Presidential Young Investigator Award, 1989-1997

Patents

GSC 12, 046-1: "Determination of antimicrobial susceptibilities on infected urines without isolation."

Picciolo, G.L., E.W. Chappelle, J.W. Deming, C.G. Shrock, H. Vellend, M.F. Barza, and L. Weinstein. 1975.

GSC 12, 045-1: "Detection of microbial infections in blood and antibiotic determinations."

Schrock, C.G., J.W. Deming, G.L. Picciolo, and E.W. Chappelle. 1976.

GSC 12, 158-1: "Rapid quantitative determination of bacteria in water."

Chappelle, E.W., G.L. Picciolo, R.R. Thomas, E.L. Jeffers, and J.W. Deming. 1978.