This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Zhulin, I B Articles by Armitage, J P Search for Related Content PubMed PubMed Citation Articles by Zhulin, I B Articles by Armitage, J P

research-article

Motility, chemokinesis, and methylation-independent chemotaxis in Azospirillum brasilense.

Department of Biochemistry, University of Oxford, England.

ABSTRACT

Observations of free-swimming and antibody-tethered Azospirillum brasilense cells showed that their polar flagella could rotate in both clockwise and counterclockwise directions. Rotation in a counterclockwise direction caused forward movement of free-swimming cells, whereas the occasional change in the direction of rotation to clockwise caused a brief reversal in swimming direction. The addition of a metabolizable chemoattractant, e.g., malate or proline, had two distinct effects on the swimming behavior of the bacteria: (i) a short-term decrease in reversal frequency from 0.33 to 0.17 s-1 and (ii) a long-term increase in the mean population swimming speed from 13 to 23 microns s-1. A. brasilense therefore shows both chemotaxis and chemokinesis in response to temporal gradients of some chemoeffectors. Chemokinesis was dependent on the growth state of the cells and may depend on an increase in the electrochemical proton gradient above a saturation threshold. Analysis of behavior of a methionine auxotroph, assays of in vivo methylation, and the use of specific antibodies raised against the sensory transducer protein Tar of Escherichia coli all failed to demonstrate the methylation-dependent pathway for chemotaxis in A. brasilense. The range of chemicals to which A. brasilense shows chemotaxis and the lack of true repellents indicate an alternative chemosensory pathway probably based on metabolism of chemoeffectors.

This article has been cited by other articles:

• Stephens, B. B., Loar, S. N., Alexandre, G. (2006). Role of CheB and CheR in the Complex Chemotactic and Aerotactic Pathway of Azospirillum brasilense. J. Bacteriol. 188: 4759-4768 [Abstract] [Full Text]  
• Mazzag, B. C., Zhulin, I. B., Mogilner, A. (2003). Model of Bacterial Band Formation in Aerotaxis. Biophys. J 85: 3558-3574 [Abstract] [Full Text]  
• Alexandre, G., Zhulin, I. B. (2001). More Than One Way To Sense Chemicals. J. Bacteriol. 183: 4681-4686 [Full Text]  
• Alexandre, G., Greer, S. E., Zhulin, I. B. (2000). Energy Taxis Is the Dominant Behavior in Azospirillum brasilense. J. Bacteriol. 182: 6042-6048 [Abstract] [Full Text]  
• Alexandre, G., Rohr, R., Bally, R. (1999). A Phase Variant of Azospirillum lipoferum Lacks a Polar Flagellum and Constitutively Expresses Mechanosensing Lateral Flagella. Appl. Environ. Microbiol. 65: 4701-4704 [Abstract] [Full Text]