For Bethany Jenkins, it's the tiny creatures that count in her two new projects

If Dr.Bethany Jenkins has anything to do with it, cars might soon be emblazoned with “Save the Microbe” bumper stickers, instead of “Save the Whales.” The sea's tiniest creatures are responsible for drawing greenhouse gases into the ocean, but pollutants such as fertilizers threaten the survival of these organisms.

Jenkins, an assistant professor in CELS’ Department of Cell and Molecular Biology, wants to understand how microbes participate in important chemical reactions, such as fixing carbon and nitrogen. Two major grants will support her efforts to investigate how microbes’ genes respond to changes in the ocean's environment and how their genes control key chemical transformations that generate food that nurture larger animals--even whales.

In the first project, Jenkins and colleagues at URI and the Woods Hole Oceanographic Institute will study the genomes of microbes known as diatoms. The single-celled algae draw carbon dioxide out of the atmosphere and fix it into biomass, which in turn helps other plankton grow, replenishing the food web. The National Science Foundation is supporting the work through a three-year, $1-million grant.

The team is led by Dr. Sonya Dyhrman of Woods Hole, and also includes Tatiana Rynearson of the URI Graduate School of Oceanography and Mak Saito at Woods Hole. ”Each of us independently saw the need to look into the issue more deeply,” says Jenkins. “Everyone brings something different to the table.”

All four scientists had been working on different aspects of diatom physiology prior to the grant so it made sense to team up. For instance, Jenkins brings knowledge of the genes that control particular chemical conversions and Rynearson provides expertise in teasing apart subtle genetic differences among populations of microbes. Dyhrman lends experience in using microbial genomics to understand cycles of ocean nutrients, and Saito focuses on how trace amounts of metals influence microbial growth. Woods Hole also provides state of the art lab equipment to analyze the entire collection of proteins in microbe.

In the first step of the project, the team will study a species of diatom typically used in laboratory studies and whose genome has already been sequenced. They will vary the amount of nutrients such as iron and phosphorus and analyze which genes the diatom turns on and off and which proteins it produces in response.

Later, the team will analyze species of diatoms that are commonly found in the ocean to find out if they use the same molecular networks to respond to nutrient changes as the lab diatom does. They will also compare the same diatom species from several parts of the ocean with different nutrient quantities.

Last spring, for instance, Jenkins and Rynearson, along with URI students, collected samples in the Atlantic Ocean’s Sargasso Sea and in the northern Pacific Ocean, which will aid these future studies. The findings should help scientists understand diatoms’ role in pulling greenhouse gases from the atmosphere and locking them into the ocean, and how environmental changes influence their contribution.

Closer to home

Jenkins’ second grant hits closer to home. In a project funded by Rhode Island Sea Grant, Jenkins is studying connections between climate change and the nitrogen cycle in Narragansett Bay. The work is a collaborative effort with Dr. Scott Nixon of the Graduate School of Oceanography and former URI graduate student Robinson Fulweiler, now a researcher at Louisiana State University.

Microbes, such as bacteria and another group of single-celled organisms known as the archaea, are the only organisms on earth capable of certain chemical conversions involving nitrogen. Humans introduce nitrogen into Narragansett Bay and other estuaries through such processes as fertilizer runoff from farms and lawns. The nitrogen surplus can cause blooms of organisms in the ocean that deplete nutrients and create dead zones. Typically, microorganisms in estuaries intervene, removing excess nitrogen through a process called denitrification.

But previously, Fulweiler and Nixon discovered that microbes in Narragansett Bay sediments had shifted from taking up nitrogen through denitrifiction to producing nitrogen through a process called nitrogen fixation. “Microbial activity has switched,” says Jenkins.

Dr. Bethany Jenkins and her research assistant, Jeremy Lins, check out the growth rates of diatoms in their Morrill Hall laboratory. Their work may provide explanations of how changes in ocean chemistry impact organisms at the base of the ocean food web.

The team isn’t sure yet why this switch occurs. But they’ve hypothesized that large spring phytoplankton blooms encourage the growth of microbes that conduct denitrification. When large blooms don’t occur, organisms that fix nitrogen dominate.

To test that idea, Jenkins, Fulweiler, and Nixon will conduct field studies and lab experiments to figure out which microbes are present, and which ones are denitrifying and which ones are fixing nitrogen. They’d like to know how resilient the system is.

“If one type of microbe disappears, can anything take its place?” asks Jenkins. Answering that question could reveal how robust the bay is at coping with human-generated nitrogen that ends up in the bay.

Humans might be exacting a doubly harsh toll on the bay, Jenkins suggests. The bay’s temperature is gradually rising over time due to climate change, and Fulweiler’s and Nixon’s analysis hints that as the bay temperature increases, phytoplankton blooms become less common. As human activity warms the planet, we might also be destroying the bay’s capacity to deal with the poisons we are pumping into it, says Jenkins. But she feels her studies will hopefully reveal ways to monitor the bay’s capacity to manipulate nitrogen and keep a watchful eye on the bay’s health.

In both projects, Jenkins will work to convey her fascination and love of science to schoolchildren. URI hired both Jenkins and Rynearson through ADVANCE, an NSF program that encourages participation of women in science, technology, engineering and math. As part of the new NSF grant, they will work with elementary- and middle-school students to improve science literacy.

And in the Narragansett Bay project, a graduate student will keep a blog aimed at high school students, explaining how she generates a hypothesis, tests the hypothesis in field studies and lab experiments, and analyzes the results. High school students can ask questions and interact with the graduate student online.

In all these efforts, Jenkins says she aims to spread the word that microbes play critical roles in maintaining the planet’s health. They might be invisible, but they’re worth saving.

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