Molecular Biology Faculty
|Lewis Thomas Lab, 353|
|Lab (609) 258-9420|
Bacterial 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.
Wilson MZ, Gitai Z. (2013) Beyond the cytoskeleton: mesoscale assemblies and their function in spatial organization. Curr Opin Microbiol. S1369-5274(13)00040-4. Pubmed
Klein EA, Gitai Z. (2013) Draft genome sequence of uropathogenic Escherichia coli strain J96. Genome Announc. 1. pii: e00245-12. Pubmed
Bos J, Yakhnina AA, Gitai Z. (2012) BapE DNA endonuclease induces an apoptotic-like response to DNA damage in Caulobacter. Proc Natl Acad Sci. 109: 18096-18101. Pubmed
Yakhnina AA, Gitai Z. (2012) The small protein MbiA interacts with MreB and modulates cell shape in Caulobacter crescentus. Mol Microbiol. 85: 1090-1104. Pubmed
van Teeffelen S, Shaevitz JW, Gitai Z. (2012) Image analysis in fluorescence microscopy: bacterial dynamics as a case study. Bioessays. 34: 427-436. PubMed
Ingerson-Mahar M, Gitai Z. (2012) A growing family: the expanding universe of the bacterial cytoskeleton. FEMS Microbiol Rev. 36: 256-266. PubMed
Barry RM, Gitai Z. (2011) Self-assembling enzymes and the origins of the cytoskeleton. Curr Opin Microbiol. 14: 704-711. PubMed
Werner JN, Gitai Z. (2010) High-throughput screening of bacterial protein localization. Methods Enzymol. 471: 185-204. PubMed
Shebelut CW, Guberman JM, van Teeffelen S, Yakhnina AA, Gitai Z. (2010) Caulobacter chromosome segregation is an ordered multistep process. Proc Natl Acad Sci. 107: 14194-14198. PubMed
Michaelis AM, Gitai Z. (2010) Dynamic polar sequestration of excess MurG may regulate enzymatic function. J Bacteriol. 192: 4597-4605. PubMEd
Shaevitz JW, Gitai Z. (2010) The structure and function of bacterial actin homologs. Cold Spring Harb Perspect Biol. 2: a000364. PubMed
Ingerson-Mahar M, Briegel A, Werner JN, Jensen GJ, Gitai Z. (2010) The metabolic enzyme CTP synthase forms cytoskeletal filaments. Nat Cell Biol. 12: 739-746. PubMed
Cowles KN, Gitai Z. (2010) Surface association and the MreB cytoskeleton regulate pilus production, localization and function in Pseudomonas aeruginosa. Mol Microbiol. 76: 1411-1426. PubMed
Werner JN, Chen EY, Guberman JM, Zippilli AR, Irgon JJ, Gitai Z. (2009) Quantitative genome-scale analysis of protein localization in an asymmetric bacterium. Proc Natl Acad Sci. 106: 7858-7863. PubMed
Gitai Z. (2009) New fluorescence microscopy methods for microbiology: sharper, faster, and quantitative. Curr Opin Microbiol. 12: 341-346. PubMed
Huang KC, Mukhopadhyay R, Wen B, Gitai Z, Wingreen NS. (2008) Cell shape and cell-wall organization in Gram-negative bacteria. Proc Natl Acad Sci 105: 19282-19287. PubMed
Guberman JM, Fay A, Dworkin J, Wingreen NS, Gitai Z. (2008) PSICIC: noise and asymmetry in bacterial division revealed by computational image analysis at sub-pixel resolution. PLoS Comput Biol. 4: e1000233. PubMed
Shebelut CW, Jensen RB, Gitai Z. (2008) Growth conditions regulate the requirements for Caulobacter chromosome segregation. J Bacteriol. 191: 1097-1100 PubMed
Silhavy TJ, Gitai Z. (2008) Sex to the rescue. Nat Methods 5: 759-760. PubMed
Gitai Z. (2007) Diversification and specialization of the bacterial cytoskeleton. Curr Opin Cell Biol 19: 5-12. PubMed
Gitai Z. (2006) Plasmid segregation: a new class of cytoskeletal proteins emerges. Curr Biol 16: R133-136. Pubmed
Gitai Z, Thanbichler M, Shapiro L. (2005) The choreographed dynamics of bacterial chromosomes. Trends Microbiol 13: 221-228. PubMed
Gitai Z, Dye NA, Reisenauer A, Wachi M, Shapiro L. (2005) MreB actin-mediated segregation of a specific region of a bacterial chromosome. Cell 120: 329-341. PubMed
Gitai Z. (2005) The new bacterial cell biology: moving parts and subcellular architecture. Cell 120: 577-586. PubMed
Dye NA, Pincus Z, Theriot JA, Shapiro L, Gitai Z. (2005) Two independent spiral structures control cell shape in Caulobacter. Proc Natl Acad Sci USA 102: 18608-18613. PubMed
Gitai Z, Dye N, Shapiro L. (2004) An actin-like gene can determine cell polarity in bacteria. Proc Natl Acad Sci USA 101: 8643-8648. PubMed
Gitai Z, Shapiro L. (2003) Bacterial cell division spirals into control. Proc Natl Acad Sci USA 100: 7423-7424. PubMed