Sallie W. Chisholm

Sallie W. Chisholm, Ph.D.

Lee and Geraldine Martin Professor of Environmental Studies
Department of Civil and Environmental Engineering
Department of Biology

Website | chisholm(replace this with the @ sign)





Project: Integrated Systems Biology of Prochlorococcus

Prochlorococcus is the single most abundant photosynthetic cell in the global oceans. Although considered a single ‘species’ by traditional measures, we now know that Prochlorococcus is made up of hundreds, if not thousands, of genetic variants that appear to be ecologically distinct. Understanding the meta-metabolism of this ‘Prochlorococcus collective’ will help us define its role in the ecosystem, and better understand its remarkable abundance and resilience. Prochlorococcus is particularly abundant in the sub-tropical Pacific Gyre – the study site of SCOPE –where it often represents over 50% of the chlorophyll. As such, it governs a sizable fraction of the energy and carbon flow in this biome, and the overall ‘input-output’ balance of the microbial communities in oligotrophic ocean ecosystems. Along with the heterotrophic bacteria, viruses, and protozoan grazers with which it interacts, Prochlorococcus represents an important node in the networks that comprise these microbially-dominated systems. One of the main goals of this project is to improve our understanding of the flow of energy and carbon through these systems by studying the ecology of Prochlorococcus at all scales of organization – from the genome to the ecosystem.


Sallie W. (“Penny”) Chisholm has been a member of the MIT Faculty since 1976, following two years of post-doctoral training at the Scripps Institution of Oceanography. She received her PhD (Biology) from the State University of NY at Albany, and her BA (Biology/Chemistry) from Skidmore College. Dr. Chisholm’s research has been focused on understanding of the role of microorganisms in shaping marine ecosystems, beginning with studies of diatoms in her early years at MIT. In 1988 she and colleagues discovered Prochlorococcus – the smallest and most abundant photosynthetic microorganism in the oceans. Since then she has devoted her research to developing Prochlorococcus as a model system for advancing our understanding of the ecology and evolution of marine microbes. This ‘integrative systems biology’ approach serves to break down barriers between traditional scientific disciplines, opening the door for new ways of thinking about living systems. In addition to her scientific pursuits, Chisholm has co-authored two award-winning children’s books on photosynthesis: Living Sunlight and Ocean Sunlight (Scholastic, 2009, 2012). She is a member of the American Academy of Arts and Sciences and the National Academy of Sciences, from which she received the Agassiz Medal in 2010. She has also received the Ramon Margalef Prize in Ecology (2013), and the National Medal of Science from the White House (2011).