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Gladys Alexandre

Contact Info

Gladys AlexandreGladys Alexandre
Professor, BCMB Head

Office : Mossman 418, (865-974-0866)
Lab: Mossman 541D

Lab Website:

Ph.D. Microbial Ecology, Université Claude Bernard, Lyon, France

Research Statement

alexandre_researchThe overall research in my laboratory focuses on characterizing at the molecular level the strategies used by bacteria to adapt to changes in the environment. Sensing of the surroundings allow cells to monitor and respond to changes in environmental conditions. We are using bacterial chemotaxis in the soil bacterium Azospirillum brasilense and the contribution of chemotaxis to the establishment of A. brasilense-cereal roots associations as a model system. Chemotaxis, the ability of motile cells to navigate in gradients of chemoeffectors, is a key determinant of the ability of diverse motile bacteria to colonize surfaces as well as to establish symbiotic, pathogenic or commensal relationships with various hosts. Bacterial chemotaxis has been well-characterized in model microorganisms such as Escherichia coli. Recent comparative genomics analyses indicate that most bacteria, in particular soil bacteria, possess multiple chemotaxis systems, the function of which is not clear and that chemotaxis signal processing in non-model bacteria is significantly more complex. A. brasilense is a tractable representative of the chemotaxis complexity found in soil-dwelling bacteria and our group has developed a suite of assays to quantitatively characterize chemotaxis responses in this species. Ongoing research addresses uses biochemistry and microbial genetics as well as mathematical modelling and engineering of novel imaging systems and organisms to address the following questions: how are signals detected and processed by two independent chemotaxis systems to produce a coordinated chemotaxis response? What are the signals perceived by chemotaxis receptors? How are metabolic cues integrated with chemotaxis signaling via chemoreceptor? How does a single chemotaxis pathway affect multiple cellular behaviors? What are the spatio-temporal dynamics of bacterial chemotaxis in the rhizosphere of plants?

Selected Publications

Russell M.H,. Bible, A. N., Fang, X., Gooding, J. R., Campagna, S. R., Gomelsky, M. and G. Alexandre (2013) Integration of the second messenger c-di-GMP into the chemotactic signaling pathway promotes sensory adaptation. mBio 4(2):e00001- 13. doi:10.1128/mBio.00001-13

Bible, A. N., Russell, M. H., and G. Alexandre (2012) The Azospirillum brasilense Che1 chemotaxis pathway controls the swimming velocity which affects transient cell-to-cell clumping. J Bacteriol 194(13):3343-3355

Siuti, P., Green, C., Edwards, A. .N., Doktycz, M. J. and G. Alexandre. (2011). The chemotaxis-like Che1 pathway has an indirect role in adhesive cell properties of Azospirillum brasilense. FEMS Microbiol Lett 323(2):105-112

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. Proc Natl Acad Sci USA 107(5):2235-2240

Bible, A., 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 Bacteriol190:6365-6375