Centre for Bacterial Cell Biology

Staff Profile

Dr Kevin Whitley

Lecturer in Microbiology

Background

I’m a biophysicist working at the intersection of single-molecule biophysics, nanotechnology, and bacterial physiology. I try to understand how bacteria grow, divide, and generally survive at a molecular level using advanced fluorescence microscopy.


My postdoc was an exciting and unique opportunity in that it was not only shared between two labs with complementary expertise in two different countries. In Cees Dekker’s lab (Department of Bionanoscience, Delft University of Technology, Netherlands) I used nanofabrication and soft lithography to design and construct microfluidic devices for immobilizing bacterial cells vertically, then used advanced microscopy in Séamus Holden’s lab (Centre for Bacterial Cell Biology, Newcastle University, UK) to image the dynamics of bacterial division machinery at a single-molecule or near-single-molecule level.


My PhD work was in single-molecule biophysics in Yann Chemla’s lab (Department of Physics, University of Illinois Urbana-Champaign, USA). I used an instrument combining fluorescence with high-resolution optical tweezers (a.k.a. “fleezers“) to look at both the elastic behavior of nucleic acids (DNA and RNA) and the detailed mechanisms of ‘motor proteins’ that unwind the DNA double-helix (helicases).

Research

Overall, we’re interested in how biomolecules inside bacteria work together as natural ‘nano-machines’ to perform the impressive engineering tasks of expanding and dividing cells.


Mechanism of bacterial cell division:


The emergence and spread of antibiotic-resistant bacteria is a major global health problem. New antibiotics—and other strategies of prevention and treatment—are urgently needed to combat this growing threat. Cell division is a major target for antibiotics, so understanding how bacterial cells divide is important for future antibiotic development. Understanding the mechanism of how bacteria divide has additional applications such as the attempt to build synthetic cells from the bottom up.


Bacterial cell division is a complex biophysical process in which many (nano-scale) proteins have to work together over large distances to build a (micro-scale) wall in the middle of the cell. I use high-resolution microscopy to see how the bacterial cytoskeleton and cell wall synthesis enzymes work together as natural nano-machines to divide cells, using the soil-dwelling bacterium Bacillus subtilis as a model system. One way I see how they work is by ‘breaking them’ – that is, watching what they do when I suddenly inhibit them with specific antibiotics, such as Penicillin G (which targets the cell wall synthesis enzymes) and PC190723 (which targets the bacterial cytoskeleton). Our work on the role of the bacterial cytoskeletal protein FtsZ in cell division is now published (Whitley, Jukes et al. Nature Communications 2021).


High-resolution imaging in bacteria:


It’s well-known that bacteria are small, and that you need powerful microscopes to see them. But, if you want to look at individual biomolecules (e.g. proteins) inside them, the situation is even worse – many bacterial cells are ~1000 nm in width, which is not much bigger than the resolution limit of the most powerful light microscopes (~250 nm)! Even worse, most bacteria—including most model systems (e.g. E. coli) and many human pathogens (e.g. M. tuberculosis)—are non-spherical, so they typically lie horizontally flat on microscope coverslips, limiting some key structures to a low-resolution side-on view.


With VerCINI (Vertical Cell Imaging by Nanostructured Immobilization), cells are trapped in tiny holes so they’re forced to stand vertically, making it far easier to image anything that happens along their shorter axes. A prototype of this method was previously developed between the Dekker and Holden labs to look at cell division in the model bacterium Bacillus subtilis (Bisson-Filho et al. Science 2017). After I joined these two labs we optimized this method, and further expanded on it by developing a separate method that combines VerCINI with microfluidics, called μVerCINI (microfluidic VerCINI) (Whitley, Jukes et al. Nature Communications 2021). With μVerCINI, we can image vertical cells in high resolution while simultaneously perturbing them with antibiotics, changing their nutrient supply, fixing them for super-resolution imaging, or many other things. We have now published a detailed protocol for both methods (Whitley et al. Nature Protocols 2022) so they can more easily be used by interested researchers.

Publications