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A road less traveled: Melissa Cregger

ORNL scientist Melissa Cregger at a switchgrass field site in Oak Ridge, Tennessee.

After traveling an unconventional path to get here, Melissa Cregger has found Oak Ridge National Laboratory (ORNL) a perfect place to accommodate, and even encourage, her diverse scientific interests.

Melissa began working at the lab as a postdoctoral researcher studying plant–microbe interactions. Now as a Liane Russell Fellow in the Biosciences Division, she is researching tree mortality and how this stress alters belowground microbial community dynamics and carbon cycling.

Melissa grew up in the small town of Lowell, Indiana. Her father was a steel mill worker (now retired), and her mother a homemaker. Melissa was the first person in her family to earn a college degree.

“It was never clear I was going to be a scientist,” Melissa said. “I took 3 years between high school and entering college. I just didn’t know what I wanted to do.”

With the intent of studying something practical, Melissa began her college career in nursing. “But after my first anatomy and physiology course, I realized I loved biological science and wanted something more,” so she switched to biology with an eye toward medical school. After taking courses in ecology, Melissa soon realized she could spend a lifetime studying either medicine or ecology.

She completed her BS degree in biology at the University of Southern Indiana, then took another 4 years before beginning graduate school. During that time, Melissa conducted surveys of endangered plants in the Algodones Dunes of Central California for the US Bureau of Land Management. “I liked the field work, but it was removed from the science; I wasn’t doing the data analysis or writing the papers,” she said.

Melissa moved to the East Coast and worked as a research assistant and manager of a pathology lab at Yale University, where she examined protein expression in a variety of cancers; later she worked for a private biotechnology firm that grew out of the lab’s research.

After 3 years in the cancer field, Melissa said she realized she missed ecology and applied to grad school. She was accepted at the University of Tennessee, Knoxville (UTK), where her mentor was eager to utilize Melissa’s skills in helping set up a new molecular biology lab.

An early introduction to the lab

During her time at UTK, Melissa was awarded a predoctoral US Department of Energy (DOE) fellowship that funded her graduate work focused on characterizing microbial community structure and function in response to climate change. It was through this program that she first met ORNL senior staff scientist Chris Schadt, who became her DOE mentor and later her postdoctoral and Russell Fellowship mentor. “It was a great introduction to the lab system and showed me the tools available there to really look at big science questions,” Melissa said.

She completed her PhD in ecology and evolutionary biology in 2012, with a dissertation focused on climate change effects on soil microbes and ecosystem function.

As a postdoc, Melissa found herself participating in human research again as she sought to merge her interests in both microbial ecology and human health. While a postdoctoral fellow at the Carl Woese Institute for Genomic Biology at the University of Illinois, she spent 2 years studying how different diseases alter the human microbiome.

She came back to ORNL in 2014 to work on the plant–microbe interfaces project, which she described as characterizing the bacterial and fungal communities associated with poplar trees from the leaves down to the roots to begin understanding how these communities function in association with the host tree. This work is ongoing, and projects have evolved to understand not only the spatial dynamics of microbial communities associated with poplar trees but also temporal dynamics and microbial community assembly.

Her Russell Fellowship research focuses on how the loss of a foundation tree species in eastern forests alters ecosystem function and aims to understand the mechanisms controlling these changes. The hemlock population in the Great Smoky Mountains National Park and elsewhere in the eastern US has been devastated by the influx of an invasive insect—the woolly adelgid. Melissa’s research examines how hemlock stress and death due to woolly adelgid attacks alter microbial community structure and litter decomposition and carbon cycling.

Melissa is already planning additional research. As part of the pending proposal to DOE for a Center for Bioenergy Innovation at ORNL, Melissa wants to examine how to naturally select microbial communities to make biofuels more sustainable—enhancing desirable feedstock plant functions such as drought resistance and increased nitrogen uptake.

Message to students: It’s OK to not have it all figured out

The “motivation for my work is that I just love science,” Melissa said. “My problem has always been that I like too many different fields in biology. But here at ORNL I’ve been able to merge my interests. In academia that might be regarded as a negative; you’re looked at as an expert in one narrow field. But at the lab, you have to be flexible because your research may change over the years. I have that flexibility and those diverse interests.”

Melissa credits the lab’s multidisciplinary, collaborative environment and tools such as high-performance computing for supporting her research. “I work with really large genomic datasets, and so having access to servers and supercomputers and top-notch bioinformaticists has been essential,” she said.

Away from the lab, Melissa cares for her young family—two children ages 3 and 1. Her 3-year-old likes to ask her if she’s going to do field work each day: “In his mind, that’s all I do.”

The scientist also enjoys mentoring students.  She typically supervises two student interns each summer at ORNL. They help her keep up with field research at two sites—one in Blount County and another in the Bledsoe State Forest on the Cumberland Plateau.

Drawing upon lessons learned in her own circuitous career path, Melissa makes a point of telling her students, “It’s OK to not know exactly what you want to do. It’s OK to take the time to figure that out.”

Her own 5-year goals? “I hope to still be here and to keep asking those questions that are interesting to me in plant, soil, and human research.”—by Stephanie Seay

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