UNIVERSITY PARK, Pa. — After a fascinating and productive scientific career, Penn State professor Marilyn Roossinck, a trailblazing researcher in virology, has announced her decision to retire.

Roossinck is an expert on viruses, from their evolutionary pressures and mechanisms to the ecology of viral diseases. She performed some of the first experimental evolutions studies on plant viruses and pioneered the first virus discovery work in a terrestrial system, by deep sequencing wild plant samples. A specialty of hers is the symbiotic relationships between plants and so-called “beneficial viruses.”

“I am most proud of the work on beneficial viruses,” she said. “This started when we found a virus in a fungus that colonized a plant growing in geothermal soils in Yellowstone National Park. The fungus was required for thermotolerance, and it turned out the virus was required, too. That started me on a pursuit of other examples of beneficial viruses, or as I like to call them, the ‘good viruses.’ This interest may have stemmed from my love of viruses — I didn’t want them to always be the bad guys!” 

Roossinck completed her undergraduate work at the University of Colorado, Boulder, receiving a biology degree in 1982. Four years later, she earned her doctorate in microbiology and immunology from the University of Colorado School of Medicine. She spent most of her career in research as an academic, but the Yellowstone work was a major turning point: “It resulted in a lot of publicity, invitations, and a new direction in research for me,” Roossinck said.

Roossinck joined Penn State as professor of plant pathology and environmental microbiology and of biology in 2011, holding appointments in the College of Agricultural Sciences and the Eberly College of Science. She taught a course in virus ecology for several years at Penn State, and said she learned more than she taught from her students and the postdocs that worked with her. She also published a popular press book about viruses.

“Marilyn repeatedly demonstrated creativity in research, collaborations and visioning for the departments and centers with which she was associated at Penn State,” said Carolee Bull, head of the Department of Plant Pathology and Environmental Microbiology and director of Penn State’s Microbiome Center. “Her colleagues and administrators were in awe of her ability to think laterally and not just think out of the box, but to create whole new boxes. 

“She is leaving a huge scientific and scholarly gap.”

Although she’s stepping away from daily research, Roossinck is too attached to the viruses to give them up completely. There’s the editorial work for multiple journals, the collaboration with a lab at Oregon State, her involvement with the American Society for Virology, and her second book about viruses. Even as her career was winding down, she still managed to find the energy for one last slam dunk: Her lab published the discovery of a reverse transcriptase activity in the polymerase of a double-stranded RNA virus in August 2021.

Roossinck credits her curiosity and enduring passion for science to her father, an enthusiastic amateur.

“He had a telescope, a microscope, and a keen interest in the world around him,” said Roossinck. “However, I did not think that you could make a career out of science. I once told my mother I wanted to be a biologist, and she said, ‘that’s not a job.’ Instead, I started pursuing a career in the health care arena, but when I took my first microbiology course and learned about viruses, I was hooked. It was an epiphany; I knew that I wanted to study viruses for the rest of my life.”