Karine Gibbs (Harvard University)
MolBio Seminar Series
Karine Gibbs is an Assistant Professor in the Department of Molecular and Cellular Biology at Harvard University. Her research group endeavors to discern the fundamental mechanisms by which cells and organisms distinguish genetic ‘self’ from ‘non-self’. They leverage the physiological simplicity and experimental tractability of a bacterium that combines a concept of self with sensing, signaling, and movement to produce sophisticated social behaviors.
Recently, Karine received a David and Lucile Packard Foundation Fellowship for Science and Engineering and a George W. Merck Fellowship. She graduated with an A.B. in Biochemical Sciences from Harvard University and a Ph.D. in Microbiology and Immunology at Stanford University. As a graduate student with Dr. Julie Theriot, she studied the cell biology of pathogens and developed tools to follow the movements of proteins on the bacterial surface. She was a Stanford Graduate Fellow, a National Science Foundation Graduate Research Fellow, and an ASM Robert D. Watkins Minority Graduate Research Fellow. Upon defending her graduate thesis, she received the Professor Sidney Raffel Award at Stanford in recognition of outstanding academic achievement in graduate studies in Microbiology and Immunology. She studied with Dr. E. Peter Greenberg for her postdoctoral fellowship at the University of Washington, where she received a University of Washington Bacterial Pathogenesis Training Grant Postdoctoral Trainee award. In Dr. Greenberg’s research group, she began her investigations of the molecular mechanisms underlying self-recognition in bacteria.
Self Versus Nonself Recognition: How a Bacterium Uses a Two-Protein Handshake to Define Identity
The ability to distinguish self from foreign, found broadly in biology, is required for many group behaviors, such as territoriality and immune recognition. At its foundation, self-recognition depends on a cell’s ability to define and communicate its (self) identity. In eukaryotes, the communication of self-identity can be complex, employing cell-specific complexes. For the bacterium Proteus mirabilis, self versus nonself-recognition is exhibited through the physical exclusion of one strain from surfaces occupied by another. This self-recognition behavior is driven by two independent multi-protein systems that intersect due to dependence on a type VI secretion system. We have recently shown that two of these self-recognition proteins bind to each other and that this interaction is chiefly limited to the variants originating from the same strain. The specificity of binding can be modulated through modifications to distinctive amino acid sequences found within a variable region of each protein. Interestingly, the in vitro binding specificity correlates with strain-specific identity in vivo. Our data support a model in which a strain-specific, two-protein complex is sufficient to define identity and mediate social behaviors dependent on self-recognition.
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