Director of Graduate Studies, Department of Molecular Biology
Faculty AssistantEllen Brindle-Clark
- Ph.D., University of California, San Francisco
- B.S., Massachusetts Institute of Technology
Research AreaMicrobiology & Virology
Research FocusBacterial cell biology: fundamentals of cytoskeletal dynamics, polarity, and mitosis
Life as we know it requires cellular asymmetry. Without asymmetry, our neurons would not process information, our intestines would not absorb nutrients, and pathogens would not be infectious. No cell is a homogeneous bag of enzymes; instead, cells have complex subcellular architectures with components that are localized to specific places at specific times. The specific architecture of each and every cell allows it to properly grow, divide, differentiate, and communicate. The mechanisms by which cells achieve their subcellular organization are thus fundamental to understanding how life works.
To study such a complicated process, we are initially focusing on a simple cell, the bacterium Caulobacter crescentus. Caulobacter has a unique life cycle during which it divides asymmetrically to produce daughters with different morphologies and fates. A rich variety of cell biological, genetic, biochemical, and genomic techniques make Caulobacter an ideal experimental system for our purposes.
The cytoskeleton plays an essential role in virtually every eukaryotic cellular process examined. Our exploration of Caulobacter cell biology has thus begun with the bacterial cytoskeleton. The absence of a cytoskeletal network was once believed to be a defining distinction between prokaryotes and eukaryotes. However, work in the past few years has shown that bacteria actually possess a full complement of cytoskeletal proteins including actin, tubulin, and intermediate filament protein homologs. The challenge remains to determine what these proteins do in the cell and how they do it.
We have initially focused on the actin homolog, MreB. During the Caulobacter cell cycle, MreB undergoes dynamic rearrangement involving a spiral that collapses into a ring, much like a slinky. Disrupting this dynamic structure dramatically perturbs cell morphogenesis, polarity, and chromosome segregation. Genetic analysis demonstrated that MreB instructs global cell polarity, while temporal studies with an MreB-inhibiting drug and MreB-ChIPs unearthed chromosomal loci that act as a centromere, directing segregation by associating with MreB. Together these results suggest that MreB plays a key role in integrating global positional information.
These findings have opened the door to several exciting avenues that we are currently pursuing. (1) Mechanistically, how does MreB direct polarity and mitosis? We are using genetic screens and biochemical assays to identify and functionally characterize MreB-interacting factors. (2) How is MreB dynamically rearranged? We are implementing new ultra-high-resolution protein labeling and imaging techniques to explore MreB’s dynamic structure. (3) Are there other key cellular regulators? We are performing a functional genomic screen to find all of the Caulobacter proteins with interesting subcellular localizations.
Our group will thus integrate cell biological, genetic, biochemical, biophysical, and genomic approaches to tackle fundamental questions in a simple model system. Eventually, I hope to investigate the similarities between prokaryotic and eukaryotic biology to provide insights into core conserved principles, and to exploit the differences for a new generation of antimicrobial targets.
How to Build a Bacterial Cell: MreB as the Foreman of E. coli Construction. Cell. 2018 ;172(6):1294-1305. .
Mitochondrial translation requires folate-dependent tRNA methylation. Nature. 2018 ;554(7690):128-132. .
Human SHMT inhibitors reveal defective glycine import as a targetable metabolic vulnerability of diffuse large B-cell lymphoma. Proc Natl Acad Sci U S A. 2017 ;114(43):11404-11409. .
Human CTP synthase filament structure reveals the active enzyme conformation. Nat Struct Mol Biol. 2017 ;24(6):507-514. .
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The effect of antibiotics on protein diffusion in the Escherichia coli cytoplasmic membrane. PLoS One. 2017 ;12(10):e0185810. .
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Mode of action and resistance studies unveil new roles for tropodithietic acid as an anticancer agent and the γ-glutamyl cycle as a proton sink. Proc Natl Acad Sci U S A. 2016 ;113(6):1630-5. .
MreB Orientation Correlates with Cell Diameter in Escherichia coli. Biophys J. 2016 ;111(5):1035-43. .
A scaffold protein connects type IV pili with the Chp chemosensory system to mediate activation of virulence signaling in Pseudomonas aeruginosa. Mol Microbiol. 2016 ;101(4):590-605. .
RodZ links MreB to cell wall synthesis to mediate MreB rotation and robust morphogenesis. Proc Natl Acad Sci U S A. 2015 ;112(40):12510-5. .
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Type IV pili mechanochemically regulate virulence factors in Pseudomonas aeruginosa. Proc Natl Acad Sci U S A. 2015 ;112(24):7563-8. .
Zemer Gitai is an Associate Professor of Molecular Biology at Princeton University. He graduated with a bachelor's degree from MIT in 1996. After completing his graduate studies at UCSF in 2002, Dr. Gitai became a postdoc in the lab of Dr. Lucy Shapiro at Stanford University where he pioneered the study of the MreB actin-like cytoskeleton in Caulobacter crescentus. Dr. Gitai joined the faculty of Princeton University as an Assistant Professor of Molecular Biology in 2005. He was promoted to Associate Professor with tenure in 2012. He is currently the Director of Graduate Studies for the Department of Molecular Biology.
Dr. Gitai's research focuses on the cell biology of bacteria. His lab studies how cells self-organize across spatial scales, using quantitative, molecular, and engineering approaches to understand to understand problems such as cell shape formation, cytoskeletal function, metabolic organization, and community structure. Dr. Gitai has published over 40 original articles in leading journals, including Cell, Molecular Cell, Nature Cell Biology, and PNAS. His work discovered new components of the bacterial cytoskeleton, new functions for bacterial polymers in metabolism, compartmentalization, and chromosome dynamics, and established the importance of protein assembly for unexpected processes like metabolism and pathogenesis. Dr. Gitai's achievements have been recognized by many prestigious awards, including the NIH New Innovator Award, the Beckman Young Investigator Award, and the HFSP Young Investigator Award.
- Pioneer Award, National Institutes of Health