Mary Ann Victoria Bruns, Ph.D.

Associate Professor of Soil Science/Microbial Ecology

A single handful of soil contains billions of microscopic organisms belonging to all three domains of life–Bacteria, Archaea, and Eukarya—as well as countless viruses infecting them. Soil that comes in contact with plant roots is transformed into a distinctive microbial habitat called the “rhizosphere,” enriched with nutrients, signal compounds, and biopolymers. Research in the Bruns Lab pursues the broad questions of, “Which rhizosphere microbial communities and functions optimize soil nutrient cycling and plant health? How do we manage soils and plants to support these communities?” Our research integrates basic and applied questions about shaping the microbiomes of soils and rhizospheres. Our current focus is on two key factors: 1) soil nitrogen (N) supply to plants (source, type, application, and timing); and 2) microbial additions (inoculations) to support beneficial plant-microbe interactions. We employ diverse methods (molecular, culture-based, and biogeochemical process measurements) to gain understanding of how soil N species and inoculation can be best managed to support agricultural productivity and improve sustainability. Because N is the most limiting nutrient for plants and because low N use efficiency results in extensive pollution and eutrophication, we investigate ways to increase biological N2 fixation through associative and free-living N2-fixing bacteria and to increase soil N retention time by applying fundamental knowledge about microbial N cycling processes. Mary Ann Bruns is Associate Professor of Soil Microbiology in the Department of Ecosystem Science and Management. She is also Director of the Biogeochemistry Dual Title Ph.D. Program and participating faculty member in the Intercollege Graduate Degree Program in Ecology. Bruns has been a long-time member of the American Society for Microbiology (ASM) and the Soil Science Society of America (SSSA). She has served as Chair of the Soil Biology and Biochemistry (S-3) Division of SSSA and President of the Allegheny Branch of ASM.