iMIC unravels model of helical cytoskeleton in bacteria

The rod-shaped bacterium Bacillus Subtilis is one of the best-studied prokaryotic cell types. It's relatively large size and well defined molecular and genetic composition make it an ideal candidate for research on diverse cell biological problems. Recent and exciting developments in live cell imaging are now allowing researchers to probe the complex dynamics of subcellular processes in bacterial cells. Till Photonics iMIC Imaging Systems provides a highly flexible, modular platform for a range of sophisticated imaging applications.

Researchers from the Max Planck Institute of Biochemistry (MPIB) and the French National Institute for Agricultural Research (INRA) have recently used an iMIC-based microscopy systems to obtain new insights into the dynamics of bacterial cell wall synthesis. Peptidoglycan (PG) polymers are arranged into a load-bearing network that maintains bacterial cell shape. It was previously thought that MreB proteins form helical structures below the membrane of bacteria, and that these helices direct cell wall growth. The researchers at MPIB and INRA now used Total Internal Reflection Fluorescence (TIRF) microscopy to image the reorganization of the MreB cytoskeleton. This technique allowed precise monitoring of protein dynamics at the cell periphery with very high image contrast. This enabled the scientists to demonstrate the formation of discrete patches that moved processively around the cells - in contrast to the continuous helical structures seen in previous studies.

The team also directly explored the turnover of MreB within motile patches by using the intuitive live Fluorescence Recovery After Photobleaching (FRAP) capability of the iMIC. They concluded that patch motility was not driven by MreB polymerization but instead by the assembly of cell wall polymers. Therefore, "MreB patches might simply act as passive scaffold for synthesis and export of PG precursors", facilitating transport and delivery of cell wall building blocks to the correct sites within the bacterium.

This study elegantly demonstrates the pioneering work that is being carried out with Till Photonics' modular and sensitive imaging solutions. The basic iMIC microscope can easily be adapted to a range of complex imaging techniques. FRAP experiments can be recorded in either widefield or TIRF illumination mode and switching between FRAP and TIRF is achieved within milliseconds thanks to the innovative Polytrope Image Mode Switch.

For information on any of these systems please visit: Till Photonics iMIC page

Find out more about this research from the Max Planck Institute of Biochemistry here: http://www.biochem.mpg.de/en/rg/wedlich/

Domínguez-Escobar, J., Chastanet, A., Crevenna, A. H., Fromion, V., Wedlich-Soldner, R. and Carballido-López, R. (2011). Processive Movement of MreB-Associated Cell Wall Biosynthetic Complexes in Bacteria. Science 333, 225-8.