Robert Barker/University Photography

Margaret McFall-Ngai, center, with students at Keeton House.

Plants and animals are far more dependent -- and interdependent -- on their trillions of microbial partners than researchers had previously realized, said microbiologist, organismic biologist and ecologist Margaret McFall-Ngai, an A.D. White Professor-at-large at Cornell, speaking on campus Sept. 25.

This discovery, made possible thanks to modern advances in molecular methods, is triggering a "revolution" in biology that has spurred a "need to come to grips with the fact that the microbial world has dominated the biosphere," said McFall-Ngai, a professor of medical microbiology and immunology at the University of Madison-Wisconsin, during her first visit to campus as an A.D. White professor Sept. 23-29.

Data shows that the vast diversity of evolved life is microbial, said McFall-Ngai, a foremost expert in the biological study of interactions between microbes and their animal hosts, adding that the evolution of plants and animals in "the last sixth" of the Earth's history has occurred on a microbe-dominated landscape.

The dependence of plants and animals on the "lethal arsenal of microbes and enzymes orchestrated by our immune system" has guided the formation of coevolved relationships with the microbial world, she said. McFall-Ngai described a similarly vital dependence of animals on the microbes of the digestive tract that colonize in the intestines and form a balanced immune system. Emphasizing the large percentage of human body functions supported by colonies of microbes, McFall-Ngai noted that the human body is actually "only 10 percent human."

The rapid evolution of microbial organisms spills over to evolution of larger-scale plants and animals, she said, whose lives depend on the work of the microbes within them and in their surroundings. Sensing changes in the small life forms upon which they depend, larger scale organisms in turn adapt physically in response. Thus, visibly notable evolutionary changes in the biosphere begin with changes in the genes of microbes.

McFall-Ngai concluded by describing the importance of integrating genetic and microbial studies with evolutionary biology to better understand evolutionary patterns.

Such integration, however, will only be possible if evolutionary scientists and microbiologists welcome this "revolution in biology" and learn to study evolution and microbiology in the contexts of one another.

During her visit, McFall-Ngai also met with faculty, graduate students, postdoctoral associates and students at Keeton House, and gave several seminars. Her six-year appointment as an A.D. White Professor-at-Large, which is co-sponsored by the President's Council of Cornell Women, runs through Jun 2017

Lauren Cue '15 is a writer intern for the Cornell Chronicle.