Bacterial motility and behaviour
Co-workers: Kathryn Scott, Mark Roberts, Mila Kojadinovic, Sonja Pawelczyk, Nicolas Delalez, Mostyn Brown, David Wilkinson, Murray Tipping, Christopher Jones, Jennifer de Beyer, Ayse Ozkan, Elaine Byles, Keith Moyles
We investigate the dynamics of bacterial sensory transduction and the control of bacterial motility. Rhodobacter sphaeroides controls the stopping frequency of its single flagellum by integrating signals from two chemosensory pathways, one responding to the extracellular environments and localised at the cell poles and one responding to the metabolic state and localised at mid cell. We are interested in the communication between the sensory and adaptation mechanisms of the two pathways as a model for sensory network integration in general.
We use techniques from ranging computerised image analysis, biochemistry, molecular genetics through to bioinformatics and computer modelling to investigate aspects of the regulation and dynamics of the sensory pathways. The output of the chemosensory pathway is regulation of the switching frequency of the bacterial rotary motor. The mechanisms involved in transducing an ion gradient into mechanical work are unclear. Using single molecule optical techniques, molecular tweezers and a regulated ion gradient we are investigating the differences between stopping and switching motors, the dynamics of the proteins within the motors and the role of the ion gradient in both rotation and motor integrity.
- Pilizota, T., Brown, M., Leake ,M. J., Branch, R., Berry, R.M. and Armitage, J.P. (2009) A molecular brake, not a clutch, stops the Rhodobacter sphaeroides flagellar motor. PNAS 106(28):11582-7
- Bell, CH, Porter, SL, Strawson, A, Stuart, DI & Armitage, JP (2010) Using structural information to change the phosphotransfer specificity of a Two-Component chemotaxis signalling complex . PLoS Biology 8(2): e1000306
- Nicolau D.V. Jr., Armitage, J.P. and Maini, P.K. (2009) Directional persistence and the optimality of run-and-tumble chemotaxis. Comp Biol Chem 33: 269-274
- Hamer, R., Chen, P-Y, Armitage, J.P., Reinert, G. and Deane, C.M. (2010) Deciphering chemotaxis pathways using cross species comparisons BMC Sys Biol, 4:3
- Ind, A. C., Porter, S.L., Brown, M.T., Byles, E.D., de Beyer, J., Godfrey, S.A. and Armitage, J.P. (2009) An inducible expression plasmid for Rhodobacter sphaeroides and Paracoccus denitrificans : AEM 75:6613-5
Figure 1: Localisation of two chemosensory pathways to different positions in a bacterial cell. Fluorescent images show localisation of two homologous chemotaxis proteins to different positions and cartoon shows the positions of the proteins in cartoon. Elongated cells show that cytoplasmic pathway proteins are positioned at single cell intervals
Figure 2: Current model of sensory flow from the chemosensory pathways to the flagellar motor. The pathways reflect the biochemistry, localisation and mathematical modelling of those data
Figure 3: Rhodobacter rotary flagella motor brakes to stop rotation, even with a full proton motive force. Figure shows rotating bacterial cell stopped by chemotaxis stimuli remaining fixed against fluid flow. Initiation of rotation reveals steps in rotation
Figure 4: Met13 provides the contact site between the histidine kinase CheA3 and the motor binding protein CheY6, ensuring only this and none of the other CheY homologues in R.sphaeroides are regulated by CheA3