Sallie Chisholm

Sallie (Penny) W. Chisholm is an Institute Professor in the Department of Biology at the Massachusetts Institute of Technology, with a joint appointment in the Department of Civil and Environmental Engineering. She earned her PhD in 1974 from the State University of New York at Albany, focusing on freshwater plankton ecology, and conducted postdoctoral research at the Scripps Institution of Oceanography. Chisholm joined MIT in 1976 as the sole biologist in Civil and Environmental Engineering and moved to the Biology Department in 1993, where she has taught introductory biology courses emphasizing ecology and advised students across biology, chemistry, oceanography, and engineering.

Chisholm's research specializes in the biology, ecology, and evolution of Prochlorococcus, the smallest and most abundant photosynthesizing cyanobacterium on Earth, which she co-discovered in 1988 and published in Nature. With cells approximately 0.5 micrometers in diameter and a global population of about 3 × 10²⁷, Prochlorococcus accounts for roughly 10% of oceanic primary production, oxygen generation, and the base of the marine food web. Her laboratory employs Prochlorococcus as a model system for cross-scale systems biology, investigating genetic diversity exceeding 80,000 genes across strains, ecotypes adapted to light, temperature, and nutrient gradients, population dynamics, viral interactions, and roles in global biogeochemical cycles. Notable publications include "Prochlorococcus: the structure and function of collective diversity" (Nature Reviews Microbiology, 2015), "Single-cell genomics reveals hundreds of coexisting subpopulations in wild Prochlorococcus" (Science, 2014), "Bacterial vesicles in marine ecosystems" (Science, 2014), and "Metabolic evolution and the self-organization of ecosystems" (PNAS, 2017). Chisholm has received the 2019 Crafoord Prize in Biosciences, 2011 National Medal of Science, 2014 MIT James R. Killian Faculty Award, 2013 Ramon Margalef Prize in Ecology, 2010 National Academy of Sciences Alexander Agassiz Medal, and fellowships from the Guggenheim Foundation (1997), AAAS (1992, 2012), and American Academy of Arts and Sciences (1992). Her discoveries have transformed understanding of marine microbial ecosystems, their evolutionary forces, and contributions to planetary oxygen and carbon cycles.