The University of Delaware Office of Graduate Studies has awarded Rex Malmstrom the 2006 Theodore Wolf Prize for outstanding dissertation in the physical and life sciences. Malmstrom, who earned his doctorate in marine studies in May 2005, received the award for his dissertation, “Contributions of Abundant Bacterial Groups to the Flux of Dissolved Organic Matter in the Ocean.”
The Theodore Wolf Prize is given annually to a University of Delaware graduate student who has completed a dissertation in the fields of either agricultural sciences, biological sciences, chemistry and biochemistry, climatology, geology, marine sciences, or physics. Malmstrom was nominated for the award by Nancy Targett, dean of the College of Marine Studies and director of the Delaware Sea Grant College Program. The winner is selected by a committee of three faculty members in the physical and life sciences.
“I am pleased to hear that my dissertation was so well received, although I was also surprised that it was honored by a University-wide prize,” says Malmstrom. “I certainly enjoyed doing the research and loved my graduate experience at the College of Marine Studies, so being awarded the Wolf prize is an incredible bonus. It also is satisfying that research in the field of marine microbial ecology was recognized by the award.”
Malmstrom’s research focused on identifying how different types of bacteria in the ocean fit into the food web — the network that shows how all organisms, from the smallest plant to the largest animal, get the food and energy they need to grow and survive. For example, some marine bacteria get their food and energy by consuming organic material that is released into the water by microscopic algae, seaweeds, and dead animals.
In particular, Malmstrom investigated a group of bacteria known as SAR11, which typically accounts for about 25% of the bacteria found in the surface waters of the ocean. He examined the growth rate of these bacteria in nature and made the first direct measurements of the specific types of organic compounds they eat.
“The bacteria provide a link between larger organisms and the organic material present in the ocean,” he says. “If the bacteria were not there, the organic material, which represents energy and nutrients, would be lost to the food web. The larger organisms get their food and energy by eating the growing bacteria.”
In addition to his work on SAR11 bacteria, Malmstrom conducted research on dimethylsulfoniopropionate, an organic sulfur compound produced by microscopic algae and released into the water column. Bacteria can convert this compound into dimethylsulfide, a climatically active gas that can enter the atmosphere.
“The release of this gas from the ocean is hypothesized to influence cloud cover,” Malmstrom says. “Differ-ent types of bacteria can consume dimethylsulfoniopropionate in ways that do not produce dimethylsulfide gas, so it’s important to identify which bacterial groups are responsible for the compound’s different fates.” Malmstrom found that a wide variety of bacterial groups can assimilate, or absorb, dimethylsulfoniopropionate, particularly Synechococcus. Previously, this bacterial group was not thought to be important in the consumption of organic matter in the ocean.
“Rex worked hard on an important problem in microbial ecology and climate-change biology, and his dissertation demonstrates this,” says Malmstrom’s adviser, David Kirchman, Maxwell P. and Mildred H. Harrington Professor of Marine Studies and associate dean of the College of Marine Studies. “His research was incredibly productive and has already changed our thinking about microbes in the oceans.”
Malmstrom began a postdoctoral position at the Massachusetts Institute of Technology in Cambridge in October 2005. Although he is still examining the links between bacterial communities and dissolved organic matter flux, he is now focusing on a different group of bacteria called Prochlorococcus. This bac-terial group also may be important to the consumption of certain types of organic matter in the ocean.
Originally from Utah, Malmstrom earned a bachelor’s degree in biology from Boston University in Massachusetts in 1999.