MacArthur Fellows Program

MacArthur Fellows / Meet the Class of 2012

Sarkis Mazmanian

Medical Microbiologist

Professor, Division of Biology

California Institute of Technology

Pasadena, CA

Age: 39

Published October 2, 2012

Sarkis Mazmanian is a microbiologist investigating the mechanisms underlying the symbiotic relationship between hosts and their beneficial microbial partners. Non-pathogenic bacteria colonize virtually every tissue type with exposure to the external environment; the enteric bacteria found in the gastrointestinal (GI) tract, which contains by far the largest number and species of bacteria, have long been known to provide benefits such as delivering certain nutrients and protection against pathogenic bacteria. In a series of studies, Mazmanian and colleagues have teased out the complex interplay between gut bacterial species and the host immune system. His results show, for example, that the probiotic species B. fragilis expresses a molecule known as polysaccharide A, which suppresses a specific immune pathway in the host that would otherwise generate an inflammatory response to a different bacterium, H. hepaticus. Absent this suppression, H. hepaticus triggers pathologic changes in the GI tract similar to ulcerative colitis and Crohn’s disease. More recently, Mazmanian found that enteric bacteria can influence the progression of immune activity in distant tissues such as the nervous system. In a mouse model of multiple sclerosis (a human autoimmune disease), he demonstrated that germ-free animals, which are otherwise resistant to induced autoimmune brain inflammation, become susceptible after their GI tract is exposed to segmented filamentous bacteria, suggesting a specific role that intestinal bacterial fauna could play in the development of autoimmune disorders in tissues distant from the intestines (e.g., the central nervous system). On the basis of his results and others’, Mazmanian has posited that harmless bacteria induce host immune tolerance by manipulating pathways that distinguish self from pathogen, a distinction that goes awry in autoimmune diseases. By elucidating the critical role of these microbes in human health, Mazmanian is laying the foundation for a new understanding of human-microbiome symbiosis that could lead to new therapies or preventive treatments for a broad class of human diseases.

Sarkis Mazmanian received a B.S. (1995) and a Ph.D. (2002) from the University of California at Los Angeles. Prior to joining the faculty of the California Institute of Technology in 2006, where he is currently a professor in the Division of Biology, he was affiliated with the University of Chicago (2002–2005) and Harvard Medical School (2005–2006). His scientific articles have appeared in such publications as Science, Nature, PNAS, and Cell.


Hi-res photos for download. Photos licensed under a Creative Commons license. Courtesy of the John D. & Catherine T. MacArthur Foundation. Right-click on the links below to save the file to your computer.

Sarkis Mazmanian In the Media

"Study Explains Stability of Our Ecosystem Within" thumbnail

"Study Explains Stability of Our Ecosystem Within"

U-T San Diego
Sarkis Mazmanian, 2012 MacArthur Fellow
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"Probing the Mysteries of Probiotics" thumbnail

"Probing the Mysteries of Probiotics"

From CNN
Sarkis Mazmanian, MacArthur Fellow, 2012
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"The Genius Series: MacArthur Winner Sarkis Mazmanian" thumbnail

"The Genius Series: MacArthur Winner Sarkis Mazmanian"

From the Los Angeles Magazine
Sarkis Mazmanian, MacArthur Fellow, 2012
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"Researchers Rethink Role of Bacteria in our Health" thumbnail

"Researchers Rethink Role of Bacteria in our Health"

From The Boston Globe
Sarkis Mazmanian, MacArthur Fellow, 2012
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"'Genius Grant' Winner Finds Humans' Closest Allies in Their Guts" thumbnail

"'Genius Grant' Winner Finds Humans' Closest Allies in Their Guts"

From the Los Angeles Time
Sarkis Mazmanian, MacArthur Fellow, 2012
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About the Fellows Program

The MacArthur Fellows Program awards unrestricted fellowships to talented individuals who have shown extraordinary originality and dedication in their creative pursuits and a marked capacity for self-direction. Learn More

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23 MacArthur Fellows Announced thumbnail

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