Gladys Alexandre, Ph.D.

 

Research Statement

Bacteria constantly monitor their environment and adapt to changing conditions by modulating the motility behavior and gene expression profiles. Bacteria respond to specific environmental signals that depend on the environment in which they find themselves in as well as their metabolic ability. My laboratory is interested in how motile bacteria use chemotaxis signal transduction pathways to detect and process environmental cues that trigger motility and other cellular responses. Research in the laboratory focuses on two microbial systems: Azospirillum brasilense and Rhizobium leguminosarum.  Both microorganisms are plant-growth promoting alpha-proteobacteria. Azospirillum brasilense forms associations with the root system of various host plants (cereals and gramineous). Rhizobium leguminosarum bv. viciae forms nodules within the roots of its host, the pea. Both bacterial species employ multiple chemotaxis signal transduction pathways and associated receptors to detect chemical gradients and modulate their motility behavior. We are interested in comparing how motility and chemotaxis contribute to the adaptation of these bacteria to their environment and the establishment of the plant-microbe associations. We are using microbial physiology and molecular genetics approaches to address these questions and determine which signals are sensed and how they are processed during chemotaxis.

Research in the laboratory is currently supported by a NSF CAREER award.

Lab Images

The many “lifestyles” of the alphaproteobacterium Azospirillum brasilense. A. brasilense can differentiate into several cell types (From top left: swarming cells, swimming cells, example of chemotaxis by swimming cells, flocculated cells and a colony on a rich medium).  Complex colony morphologies resulting from the coordinated activities of cells within different zones of the colony are often observed.

Selected Publications

Siuti, P., C. S. Green, A. N. Edwards, M. Doktycz and G. Alexandre. The chemotaxis-like Che1 pathway has an indirect role in adhesive cell properties of Azospirillum brasilense. FEMS Microbiology Letters (In press)

Edwards, A. N., P. Siuti, A. N. Bible, G. Alexandre, S. T. Retterer, M. J. Doktycz and J. L. Morrell-Falvey (2011). Characterization of cell surface and extracellular matrix remodeling ofAzospirillum brasilense chemotaxis-like 1 signal transduction pathway mutants by atomic force microscopy. FEMS Microbiology Letters 314(2):131-139.

Alexandre, G. (2010) Coupling metabolism and chemotaxis-dependent behaviours by energy taxis receptors. Microbiology 156:2283-2293

Xie, Z., Ulrich, L. E., Zhulin, I. B. and G. Alexandre (2010) PAS domain containing chemoreceptor couples dynamic changes in metabolism with chemotaxis. Proceedings of the National Academy of Sciences USA 107(5):2235-2240            

Buchan, A., Crombie, B. and G. M. Alexandre (2010) Temporal dynamics and genetic diversity of chemotactic-competent microbial populations in the rhizosphere. Environnmental Microbiology12 (12): 3171-3184.

Wasim, M., A. N. Bible, Z., Xie, and G. Alexandre (2009) Alkyl hydroperoxide reductase has a role in oxidative stress resistance and in modulating changes in cell surface properties in Azospirillum brasilense Sp245. Microbiology  155:1192-11202

Miller, L. D., Russell, M. H. And G. Alexandre (2009) Diversity in bacterial chemotactic responses and niche adaptation. Adv. Appl. Microbiol. 66:53-75

Alexandre, G. (2008) A sense of self-worth: energy taxis provides insight into how Helicobacter pylori navigates through its environment. J Bacteriol 190:3095-3097 (Guest Commentary)

Bible, A. N., B. B. Stephens, D. R. Ortega, Z. Xie and G. Alexandre (2008) Function of a chemotaxis-like signal transduction pathway in modulating motility, cell clumping and cell length in the alpha-proteobacterium Azospirillum brasilense. J. Bacteriol. 190:6365-6375

Miller, L. D., C. K. Yost, F. Hynes and G. Alexandre* (2007) The major chemotaxis gene cluster of Rhizobium leguminosarum bv. viciae is essential for competitive nodulation. Molecular Microbiology 63 (2): 348-362.

*Corresponding author

 

Contact Information

Office:
Room F-425
Walters Life Sciences
Phone: (865) 974-0866

Lab:
Room D-403
Room D-407
Walters Life Sciences
Phone: (865) 974-2364

Email: galexan2@utk.edu