One key area in understanding bacterial cell biology is spatiotemporal phenomena: Where, when, and how do individual biomolecules act and interact to govern the overall physiology of the cell? To answer this question, we develop new high-resolution imaging methods for 3D single-molecule localization in intact bacterial cells. In particular, we combine the resolving power of the electron microscope with the single-molecule sensitivity and specificity of fluorescence-based methods. With these tools, we can localize single biomolecules in 3D space with a precision of a few nanometers, track their motion over time, and then zoom in further to visualize how specific biomolecules combine with others to produce functioning assemblies in their native environment.
Bacteria are highly relevant to important challenges of our time. For example, the looming inability to effectively combat pathogenic bacteria with current antibiotics presents a major health concern. Finding new avenues to selectively target and alter key molecular pathways can provide us with further options for effective antibiotic drug development. Because bacteria are the smallest and arguably the simplest living organisms on the planet, they are also fundamentally interesting to study the molecular-level biology of the cell. Bacteria are able to precisely regulate protein activity throughout the intracellular space through finely tuned molecular interactions. Of particular importance are scaffolding proteins that partition the cytoplasm and provide specialized subcellular compartments for specific biochemical reactions to occur. On a smaller scale, scaffolding proteins are hypothesized to spatially organize multiple enzymes into biomolecular assemblies. Parts of these assemblies can be highly dynamic and therefore the precise architectures and the resulting functional consequences remain elusive.
Rapid progress of evolution has made the bacteria an extremely diverse and widely abundant group of single-celled organisms that affects almost every aspect of live on earth. The resulting bacterial physiological traits present a biological treasure trove that remains to be investigated with molecular resolution and, where possible, exploited to our benefit. With this in mind, we continue to push the limits of cellular imaging, as well as in situ structural characterization of biomolecular assemblies.
Bacterial Scaffold Directs Pole-Specific Centromere Segregation. J.L. Ptacin, A. Gahlmann, G.R. Bowman , A.M. Perez, A.R.S. von Diezmann, M.R. Eckart, W.E. Moerner, and L. Shapiro. Proc. Natl. Acad. Sci. USA, 2014, 111, E2046
Exploring Bacterial Cell Biology with Single-Molecule Tracking and Super-Resolution Imaging. A. Gahlmann and W.E. Moerner. Nat. Rev. Microbiol., 2013, 12, 9 (Cover Article)
Quantitative Multicolor Subdiffraction Imaging of Bacterial Protein Ultrastructures in Three Dimensions. A. Gahlmann, J.L. Ptacin, G. Grover, S. Quirin, A.R.S. von Diezmann, M.K. Lee, M.P. Backlund, L. Shapiro, R. Piestun, and W.E. Moerner. Nano Lett., 2013, 13, 987
Direct Structural Determination of Conformations of Photoswitchable Molecules by Laser Desorption-Electron Diffraction. A. Gahlmann, I-R. Lee, and A.H. Zewail. Angew. Chem. Int. Ed., 2010, 49, 6524
Structure of Isolated Biomolecules by Electron Diffraction-Laser Desorption: Uracil and Guanine. A. Gahlmann, S.T. Park, and A.H. Zewail. J. Amer. Chem. Soc., 2009, 131, 2806 (Cover Article)
Ultrashort Electron Pulses for Diffraction, Crystallography and Microscopy: Theoretical and Experimental Resolutions. A. Gahlmann, S.T. Park, and A.H. Zewail. Phys. Chem. Chem. Phys., 2008, 10, 2894