Our quest is an understanding of the behavior of bacteria at the molecular level, especially behavior involving chemical stimuli (chemotaxis)

Flagellated bacteria possess a remarkable motility system based on a reversible rotary motor linked by a flexible coupling (the proximal hook) to a thin helical propeller (the flagellar filament). The motor derives its energy from chemiosmotic mechanisms, from protons driven into the cell by chemical gradients or electrical fields.  The direction of rotation of the motor depends, in part, on signals generated by sensory systems, the best studied of which analyzes chemical stimuli.  Our group is trying to learn how the motor works, what the signal is that controls its direction of rotation,and how this signal is processed by the chemical sensory system.  These questions are being approached by a variety of molecular-genetic and physical techniques, including fluorescence resonance energy transfer.  This technique has made possible measurements of the activity of labile components of the sensory transduction pathway in vivo and exploration of an early amplification step based on receptor-receptor interactions.  Recent discoveries include the finding that the flagellar motor adapts, adding components that increase its sensitivity to the chemotaxis response regulator or that increase the generation of torque.  The goal is an understanding of chemiosmotic coupling and sensory transduction at the molecular level.  Other work includes attempts to use bacterial carpets as actuators in microfluidic systems and studies of the motility of bacteria that glide, some by mechanisms that are completely mysterious.

Selected Publications:

Berg, H.C. The rotary motor of bacterial flagella. Annu. Rev. Biochem. 72, 19-54 (2003). Berg, H.C. E. coli in Motion. (Springer-Verlag, NY, 2004).

Yuan, J., Branch, R., Hosu, B.G., and Berg, H.C. Adaptation at the output of the chemotaxis signalling pathway. Nature 484, 233-236 (2012).

Turner, L., Stern, A.S., and Berg, H.C. Growth of flagellar filaments of Escherichia coli is independent of filament length. J. Bacteriol. 194, 2437-2442 (2012).

Ping, L., Wu, Y., Hosu, B.G., Tang. J.X., and Berg, H.C. Osmotic pressure in a bacterial swarm. Biophys. J. 107, 1-8 (2014).