Doctoral Candidate Bradley Tolar travels the world studying marine microorganisms essential for life


Collecting RNA from water samples in the Gulf of Alaska

Bradley Tolar, a doctoral candidate in the Department of Microbiology, sails to such unusual environments as the Southern Ocean off the coast of Antarctica and the Gulf of Alaska to collect specific types of marine microorganisms essential for life on earth.

These microorganisms, named Thaumarchaetoa, make up about 30 percent of all single-celled microorganisms (a figure that is roughly 10,000 times more numerous than the stars in the universe) and are responsible for converting wastewater and dangerous chemicals into non-toxic compounds as part of the nitrogen cycle.

These microorganisms are extremely numerous in cold waters devoid of light, but their future remains questionable as the earth’s weather patterns begin to change.


Collecting water samples in the Gulf of Alaska.

Antarctica research trip.

In Antarctica for example, Thaumarchaetoa are highly abundant in the winter but disappear once temperatures and sunlight exposure rates begin to increase. While this is a normal cycle, the growing ozone hole brings with it the increasing threat of solar radiation reaching surface waters (which raises questions about their future survival).

Although sunlight and temperature do not have a direct impact on these microorganisms, Tolar speculates that reactive oxygen species (ROS), a compound formed through the interaction of solar radiation and carbon, is potentially toxic to them.


Working with water samples in the Gulf of Mexico

“With the world currently in a state of change, increased radiation from the sun could have major effects on Thaumarchaetoa populations as a whole and thus the nitrogen cycle itself,” explains Tolar.

In the first research of its kind to investigate the relationship between Thaumarchaetoa and ROS, Tolar researches the effect of climate change and the ozone hole on populations of Thaumarchaetoa.

With the help of funding from his advisor, Dr. James T. Hollibaugh, Tolar has collected samples of these microorganisms from the Gulf of Mexico, the Southern Ocean off the coast of Antarctica, Sapelo Island off the coast of Georgia, and the Gulf of Alaska.

By studying the distinct differences in each sample of Thaumarchaetoa and making slight changes in water temperature and pH level, Tolar has been able to determine each population’s distinct reaction to ROS.


Research Vessel Laurence M. Gould - Antarctica Research Cruise

Recent results of Tolar’s study confirm that increased concentrations of ROS decrease Thaumarchaeota’s ability to oxidize ammonia, but Tolar also found that certain populations of the marine microorganism, specifically those collected from Sapelo Island, have developed some resistance to ROS.

After graduation, Tolar plans to further his work with Thaumarchaeota as a postdoctoral research associate. He looks forward to an academia position teaching and conducting research in his own lab as a professor.