Decadal Shifts in Microbial Ecology: James Tiedje Discusses
Source: Michigan State University
To celebrate Tiedje’s 80th birthday, former students and colleagues from across the globe will come together to honor his contributions to the field. From April 4-6, 2022, The International Forum on Advanced Science and Technology (iFAST) is hosting a highlighting a broad range of microbial ecology, environmental microbiology and computational biology research topics. Speakers hail from all over the world, and many of them represent Tiedje’s former students, postdocs and visiting scholars, some of whom are second-generation connections.
We had the privilege of speaking with Tiedje before the event, in what rapidly became an engaging conversation about pioneering new spaces in science and remaining ever-adaptable to the environmental changes one encounters in their career.
“I sort of grew up with the field,” Tiedje explained. Inspired by Rachel Carson’s, Silent Spring, and a summer as an undergraduate student spent mapping rhizobium serotypes of nodules associated with soy beans across the state of Iowa, Tiedje entered a field of research that was in its infancy. He attended graduate school at Cornell University from 1964-68, when microbial ecology was just beginning to take shape. His graduate school professor, Martin Alexander, along with Tom Brock, from the University of Wisconsin, were the 2 early figures in the field. Tiedje’s first research project was on metabolism of , and subsequently in insecticides in soil. “My job was to work out the pathway of 2,4-D degradation. That’s how I began,” Tiedje explained.
He continued to study pesticide biodegradation when he accepted a position post-graduation as assistant professor at Michigan State University. At that time, this was still a new topic area, and research surrounding it remained primarily academic in nature. There were attempts throughout the 1960s to pass legislation for federal regulation of pesticides, but it was the creation of the Environmental Protection Agency (EPA) in 1970, and growing public concern about the adverse effects of pesticides on human and wildlife health, that enabled an overhaul of pesticide regulation, giving the EPA authority to refuse registration to any pesticide that posed risks, outweighing the benefits of use, to humans, wildlife and/or the environment.
In 1976, the Toxic Substances Control Act brought attention to other chemicals that reach the environment and called for information about their persistence, toxicity and bioaccumulation. As a result, Tiedje expanded his work to evaluate the fate of certain high-volume chemicals, including Polychlorinated biphenyls (PCBs), a highly toxic organic chlorine compound used as a dielectric and coolant fluid; Dichlorodiphenyltrichloroethane (DDT), a chemical widely used to control insect populations since the early WWII days; and chlorinated solvents, which are widely used in manufacturing, the electronics industry, in the air force (to keep jet planes clean) and in the dry-cleaning industry.
In the 1980’s Tiedje and colleagues discovered soil microbes that dechlorinate chlorine aromatic compounds, including PCB, DDT and chlorinated solvents. Ideally, from an environmental point of view, if the microbes can take off all of the chlorine molecules, the structure is more easily degraded to CO2. With some chemicals complete degradation can occur. But for many years, researchers could not get PCBs completely degraded. A multi-pronged approach proved useful. “We could get most of the chlorines off, and then aerobic microbes had a chance to degrade the rest of the molecule,” Tiedje shared.
In the new millennium, Tiedje turned his attention to antibiotic resistance, treating antimicrobial resistant organisms as a different kind of environmental pollutant—one that is microbially based. “There are various uses of antibiotics, including human use and misuse and agricultural use," Tiedje explained. Antibiotics are widely used for growth promotion in pig and chicken production, and for shellfish and fish production in Southeast Asia. Furthermore, production facilities are regulated differently in different parts of the world. “The idea is to determine what’s risky,” Tiedje elaborated, with a downstream goal of restricting practices that pose significant risk to the development and spread of increased antimicrobial resistance.
Tiedje’s research has also focused on the microbial communities themselves, investigating the metagenomics and microbiome of different habitats and looking at processes of denitrification. He noted that environmental issues go hand-in-hand with knowledge gained from molecular methods about microbial communities, explaining that molecular tools can be used to answer pressing questions. “One of my big themes is how decadal changes have impacted our science over time—what drove those changes and how things might continue to change in the future,” he shared in reference to the intersections between advancements in molecular research and the field of microbial ecology.
When asked what advice he has for future generations of scientists seeking to stay adaptable to their own ever-changing environments, Tiedje shared, “Try to have some vision for the future. Consider not only what you see now, but also what you think the future will bring. Then, try to get some background in that area, so that when it does come, you're in a good position to take advantage of those new things.”
Tiedje considers the opportunity to work with “excellent and inspiring students” the most rewarding aspect of his career. “That’s what brings the scientific results, which are, in turn, rewarding for everyone,” he stated.
