This Article Full Text 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 Greer-Phillips, S. E. Articles by Alexandre, G. Search for Related Content PubMed PubMed Citation Articles by Greer-Phillips, S. E. Articles by Alexandre, G.

An Energy Taxis Transducer Promotes Root Colonization by Azospirillum brasilense

Suzanne E. Greer-Phillips,^1, Bonnie B. Stephens,² and Gladys Alexandre^1,2*

Department of Microbiology and Molecular Genetics, School of Medicine, Loma Linda University, Loma Linda, California,¹ Department of Biology, Georgia State University, Atlanta, Georgia²

Received 23 April 2004/ Accepted 6 July 2004

Motility responses triggered by changes in the electron transport system are collectively known as energy taxis. In Azospirillum brasilense, energy taxis was shown to be the principal form of locomotor control. In the present study, we have identified a novel chemoreceptor-like protein, named Tlp1, which serves as an energy taxis transducer. The Tlp1 protein is predicted to have an N-terminal periplasmic region and a cytoplasmic C-terminal signaling module homologous to those of other chemoreceptors. The predicted periplasmic region of Tlp1 comprises a conserved domain that is found in two types of microbial sensory receptors: chemotaxis transducers and histidine kinases. However, the function of this domain is currently unknown. We characterized the behavior of a tlp1 mutant by a series of spatial and temporal gradient assays. The tlp1 mutant is deficient in (i) chemotaxis to several rapidly oxidizable substrates, (ii) taxis to terminal electron acceptors (oxygen and nitrate), and (iii) redox taxis. Taken together, the data strongly suggest that Tlp1 mediates energy taxis in A. brasilense. Using qualitative and quantitative assays, we have also demonstrated that the tlp1 mutant is impaired in colonization of plant roots. This finding supports the hypothesis that energy taxis and therefore bacterial metabolism might be key factors in determining host specificity in Azospirillum-grass associations.

Present address: Department of Plant Pathology, University of California at Riverside, Riverside, CA 92521.

This article has been cited by other articles:

• Yao, J., Allen, C. (2007). The Plant Pathogen Ralstonia solanacearum Needs Aerotaxis for Normal Biofilm Formation and Interactions with Its Tomato Host. J. Bacteriol. 189: 6415-6424 [Abstract] [Full Text]  
• Ryjenkov, D. A., Simm, R., Romling, U., Gomelsky, M. (2006). The PilZ Domain Is a Receptor for the Second Messenger c-di-GMP: THE PilZ DOMAIN PROTEIN YcgR CONTROLS MOTILITY IN ENTEROBACTERIA. J. Biol. Chem. 281: 30310-30314 [Abstract] [Full Text]  
• 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]  
• Yao, J., Allen, C. (2006). Chemotaxis Is Required for Virulence and Competitive Fitness of the Bacterial Wilt Pathogen Ralstonia solanacearum.. J. Bacteriol. 188: 3697-3708 [Abstract] [Full Text]  
• Amikam, D., Galperin, M. Y. (2006). PilZ domain is part of the bacterial c-di-GMP binding protein. Bioinformatics 22: 3-6 [Abstract] [Full Text]