Organization and Dynamics of Bacterial DNA Book

We are working to biophysically characterize the dynamics of segregation and partitioning of DNA within bacteria. Our single-molecule experiments will provide constraints to models of DNA segregation and maintenance. The results will provide us with a much deeper appreciation for how bacterial cells distribute their genetic material during cell division and lead to insight within the vastly more complicated world of the eukaryotic chromosome where functional errors in genome replication and partitioning can have grave implications for our understanding of health and disease.

Switching Foreign Genes On and Off in Bacteria by Packaging the Chromosome Book

Silencing proteins like the histone-like nucleoid structuring protein (H-NS) form nucleoprotein complexes along AT rich regions of DNA. In this way they are able to detect and inactivate foreign DNA acquired through horizontal gene transfer. These proteins are an important regulator of both the drug resistance and virulence of bacteria. We are using single-molecule tools to uncover the biophysical mechanisms by which this important class of proteins function.

Super-Resolved Localization Microscopy

In recent years, a variety of super-resolution techniques have been developed that overcome the diffraction limit imposed upon optical microscopy. 3D STORM/PALM microscopy uses photo-switchable fluorescent probes to spatially localize individual fluorescent labels whose signals would otherwise overlap. This method can achieve lateral (axial) image resolutions of approximately 20 nm (50 nm).

(Left) RNA Pol II distribution in the nucleus of a mouse neuronal cell. (Center/Right) Images of our home-built localization microscope.

Optical Force Spectroscopy (Optical Tweezers)

Optical trapping is one of the most valuable modern-day tools for quantitative research in biological and soft condensed matter physic. Optical tweezers allow for real-time measurements of sub-nanometer displacements and the application of piconewton forces. The meteoric progress of the past few decades in developing techniques to study single macromolecules, has unveiled the mechanistic operation of both the translational and transcriptional machinery involved in gene expression at an unprecedented level of quantitative detail, providing a level of insight into function that is unattainable with bulk measurements alone. At the horizon, lies the challenge to drive these methods into the cellular arena, to both witness and influence single molecular events within living cells.

Illustration of an optical trap (left) and image (right) of our current optical tweezers setup in the lab.