Howard C. Berg

Department of Molecular & Cellular Biology and Department of Physics
Harvard University
Biological Laboratories 3063
16 Divinity Avenue, Cambridge, MA 02138

tel: (617) 495-0924; fax: (617) 496-1114

Bacterial Motility and Behavior

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 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. Professor Berg's 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, most recently by 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. 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:

Turner, L., Ryu, W.S. and Berg, H.C. Real-time imaging of fluorescent flagellar filaments. J. Bacteriol.,182, 2793-2801 (2000).

Skerker,, J.M. and Berg, H.C. Direct observation of extension and retraction of type IV pili. Proc. Natl. Acad. Sci. USA 98, 6901-6904 (2001).

Sourjik, V. and Berg, H.C. Receptor sensitivity in bacterial chemotaxis. Proc. Natl. Acad. Sci. USA 99, 123-127 (2002).

Berg, H.C. The rotary motor of bacterial flagella. Annu. Rev. Biochem. 72, 19-54 (2003).

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