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Journal of Bacteriology, June 2006, p. 3962-3971, Vol. 188, No. 11
0021-9193/06/$08.00+0     doi:10.1128/JB.00149-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Differential Activation of Escherichia coli Chemoreceptors by Blue-Light Stimuli

Stuart Wright,1 Bharat Walia,1 John S. Parkinson,2 and Shahid Khan1*

Molecular Biology Consortium, Chicago, Illinois 60612,1 Biology Department, University of Utah, Salt Lake City, Utah 841122

Received 26 January 2006/ Accepted 15 March 2006

Enteric bacteria tumble, swim slowly, and are then paralyzed upon exposure to 390- to 530-nm light. Here, we analyze this complex response in Escherichia coli using standard fluorescence microscope optics for excitation at 440 ± 5 nm. The slow swimming and paralysis occurred only in dye-containing growth media or buffers. Excitation elicited complete paralysis within a second in 1 µM proflavine dye, implying specific motor damage, but prolonged tumbling in buffer alone. The tumbling half-response times were subsecond for onset but more than a minute for recovery. The response required the chemotaxis signal protein CheY and receptor-dependent activation of its kinase CheA. The study of deletion mutants revealed a specific requirement for either the aerotaxis receptor Aer or the chemoreceptor Tar but not the Tar homolog Tsr. The action spectrum of the wild-type response was consistent with a flavin, but the chromophores remain to be identified. The motile response processed via Aer was sustained, with recovery to either step-up or -down taking more than a minute. The response processed via Tar was transient, recovering on second time scales comparable to chemotactic responses. The response duration and amplitude were dependent on relative expression of Aer, Tar, and Tsr. The main response features were reproduced when each receptor was expressed singly from a plasmid in a receptorless host strain. However, time-resolved motion analysis revealed subtle kinetic differences that reflect the role of receptor cluster interactions in kinase activation-deactivation dynamics.

* Corresponding author. Mailing address: Molecular Biology Consortium, 2201 W. Campbell Park Drive, Chicago, IL 60612. Phone: (312) 996-1216. Fax: (312) 413-2952. E-mail: ShahidKhan{at}mbclss.org.

Journal of Bacteriology, June 2006, p. 3962-3971, Vol. 188, No. 11
0021-9193/06/$08.00+0     doi:10.1128/JB.00149-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Darnton, N. C., Turner, L., Rojevsky, S., Berg, H. C. (2007). On Torque and Tumbling in Swimming Escherichia coli. J. Bacteriol. 189: 1756-1764 [Abstract] [Full Text]  


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