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.
Selected Publications
Stephens BB, Loar SN and Alexandree G (2006) Role of CheB and CheR in the complex chemotactic and aerotactic pathway of Azospirillum brasilense. J. Bacteriol. 188: 4759-4768.
Su S, Stephens BB, Alexandre G and Farrand SK (2006) Lon protease of the alpha-proteobacterium Agrobacterium tumefaciens is required for normal growth, cellular morphology and full virulence. Microbiology 152: 1197-1207.
Greer-Phillips SE, Stephens BB and Alexandre G (2004) An energy-taxis transducer promotes root colonization by Azospirillum brasilense. J. Bacteriol. 186: 6595-6604.
Alexandre G, Greer-Phillips SE and Zhulin IB (2004) Ecological role of energy taxis in microorganisms. FEMS Microbiol. Rev. 28: 113-126.
Alexandre G and Zhulin IB (2003) Different evolutionary constraints on chemotaxis proteins CheW and CheY revealed by heterologous expression studies and protein sequence analysis. J. Bacteriol. 185: 544-552.
Greer-Phillips SE, Alexandre G, Taylor BL and Zhulin IB (2003) Aer and Tsr guide Escherichia coli in spatial gradients of oxidizable substrates. Microbiology 149: 2661-2667.
Hauwaerts D, Alexandre G, Das SK, Vanderleyden J and Zhulin IB (2002) A major chemotaxis gene cluster in Azospirillum brasilense and relationships between chemotaxis operons in alpha-proteobacteria. FEMS Microbiol. Lett. 208:61-67.
Alexandre G and Zhulin IB (2001) More than one way to sense chemicals. J. Bacteriol. 183:4681-4686.
Alexandre G, Greer SE and Zhulin IB (2000) Energy taxis is the dominant behavior in Azospirillum brasilense. J. Bacteriol. 182:6042-6048.
Alexandre G and Zhulin IB (2000) Laccases are widespread in bacteria. Trends Biotechnol. 18:41-42.
Alexandre G, Bally R, Taylor BL and Zhulin IB (1999) Loss of cytochrome c oxidase activity and acquisition of resistance to exogenous quinones in a laccase-positive variant of Azospirillum lipoferum. J. Bacteriol. 181:6730-6738.
Alexandre G, Rohr R and 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.
Alexandre G and Bally R (1999) Emergence of a laccase-positive variant of Azospirillum lipoferum occurs via a two-step phenotypic switching process. FEMS Microbiol. Lett. 174:371-378.
Alexandre G, Jacoud C, Faure D and Bally R (1996) Population dynamics of a motile and non-motile Azospirillum lipoferum strain during rice colonization and motility variation in the rhizosphere. FEMS Microbiol. Ecol. 19:271-278.
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