Elizabeth (Betsy) Pierson
Associate Professor
Plant Microbe Interactions
Office: 427 HFS Building; Lab: 404 HFSB
TAMU 2133
College Station, TX 77803
Email: eapierson@tamu.edu
Phone: Office: 979 862-1307; Lab: 979-862-4259
Dr. Pierson is a member of the graduate faculty of Texas A&M University. She also is an Adjunct Associate Professor in the Department of Plant Pathology and Microbiology and a member of the intercollegiate faculty of Molecular and Environmental Plant Sciences (MEPS).
- Educational Background:
- Career Experience:
A major focus of the lab’s work is on understanding microbe-microbe, microbe-plant, or microbe-insect interactions in plant-associated or insect-associated biofilm communities. Ultimately, we hope the study of microbial community interactions at population and genetic levels will provide a better understanding of the control points involved in the establishment and dynamics of microbial communities (including those that cause disease or protect the host from disease) on plants. Our work has focused on the ecological significance of molecular signaling via the production of N-acyl-homoserine lactone signals (AHL’s) between bacterial populations on plant roots. This mechanism of cell-cell communication enables bacterial strains co-inhabiting plant surfaces to influence the outcome of competition by affecting the regulation of physiochemical behaviors at a genetic level. Our model system, Pseudomonas chlororaphis (aureofaciens) strain 30-84, is an effective biological control agent for wheat take-all disease caused by the fungal pathogen Gaeumannomyces graminis var. tritici. This bacterium has two quorum-sensing (QS) systems that modulate the expression of genes involved in phenazine antibiotic production, exoprotease activity, and cell surface characteristics. Expression of these genes affects the ability of our strain to survive and compete with other microorganisms (including other bacteria and fungal pathogens). We demonstrated that a subset of the bacteria inhabiting the wheat rhizosphere produce diffusible signals that positively communicate with strain 30-84 (e.g. their signals also could activate gene expression in strain 30-84). Subsequently, we discovered a small subset of the population that negatively communicate with strain 30-84 (e.g. their signals could down-regulate QS in strain 30-84). We also found that the two QS regulatory systems and the phenazine antibiotics under QS control are involved in biofilm formation by strain 30-84. Current work with this model system focuses on other roles of phenazines in microbial community interactions and how expression of different phenazine derivatives affects these interactions.
Other areas of research in microbial ecology include our discovery of a novel mutation that bypasses the need for QS and enables phenazines to be expressed in a non-QS dependent manner. This same regulatory gene exists in a number of interesting pseudomonads including the human pathogen Pseudomonas aeruginos, where it regulates the production of the phenazine, pyocyanin. Previously, we participated in a Pseudomonas sequencing project funded as part of the FY 2000 Microbial Genome Initiative (USDA/NSF). This project was a collaborative effort between researchers at the USDA-ARS in Corvallis, OR and Pullman, WA, Oregon State University, the University of Arizona, and The Institute for Genomic Research and resulted in the publication of the genome sequence of Pseudomonas fluorescens strain Pf-5. Continuing work by the collaborative group includes the sequencing of multiple Pseudomonas biological control strains including P. chlororaphis strain 30-84. Collaborative work with graduate student Anne Estes and others is focused on understanding the dynamics endosymbiotic bacterial populations in insects and plants.
I also maintain a research interest in the dynamics of native and invasive introduced plant species.
Affiliations:
Member of the American Phytopathological Society
Selected Publications in Microbial Ecology:
A.M. Estes, D.J. Hearn, J. Bronstein, E.A. Pierson. The olive fly endosymbiont, 'Candidatus Erwinia dacicola', switches from an intracellular to an extracellular existence during host insect development (accepted Applied and Environmental Microbiology).
VSRK Maddula, EA Pierson, and LS Pierson III. 2009. Altering the Ratio of Phenazines in Pseudomonas chlororaphis (aureofaciens) 30-84: Effects on Biofilm Formation and Pathogen Inhibition. J. Bacteriol. 190(8):2759-66.
Pierson, LS, III, and EA Pierson. 2007. Roles of Diffusible Signals in Communication among Plant-Associated Bacteria. Phytopathology 97:227-232).
VSRK Maddula, Zhang, Z, EA Pierson, and LS. Pierson III. 2006. Quorum sensing and phenazines are involved biofilm formation by Pseudomonas chlororaphis (aureofaciens) Strain 30-84. Microbial Ecology 52(2): 289-301.
Paulsen, IT, Press, C., Ravel, J, Kobayashi, DY, Myers, GSA, Mavrodi, DV, DeBoy, RT, Seshadri, R, Ren, Q, Madupu, R, Dodson, RJ, Durkin, AS, Brinkac, LM, Daugherty, SC, Sullivan, SA, Rosovitz, MJ, Gwinn, ML, Zhou, L, Nelson, WC, Weidman, J, Watkins, K, Tran, K, Khouri, H, Pierson, EA, Pierson, LS III, Thomashow, LS, and Loper, JE. 2005. Complete genome sequence of the plant commensal Pseudomonas fluorescens Pf-5: insights into the biological control of plant disease. Nature Biotechnology 23(7):873-8.
Morello, JE, EA Pierson, and LS Pierson III. 2004. Negative cross-communication among wheat rhizosphere bacteria: Effect on antibiotic production by the biological control bacterium Pseudomonas aureofaciens 30-84. Applied and Environmental Microbiology, 70(5):3103-9.
Loh, J, Pierson, EA, Pierson, LS III, Stacy, G, and A. Chatterjee. 2002. Quorum sensing in plant-associated bacteria. Current Opinion in Plant Biology 5:1-5.
Chancey, S. T., D. W. Wood, E. A. Pierson, and L. S. Pierson III. 2002. Survival of GacS/GacA mutants of the biological control bacterium Pseudomonas aureofaciens 30-84 in the wheat rhizosphere. Applied and Environmental Microbiology 68: 3308-3314.
Pierson, E. A., D. W. Wood, J. A. Cannon, F. M. Blachere, and L. S. Pierson III. 1998. Interpopulation signaling via N-acyl homoserine lactones among bacteria in the wheat rhizosphere. Molecular Plant Microbe Interactions 11:1078-1084.
Pierson, L. S. III, D. W. Wood, and E. A. Pierson. 1998. Homoserine lactone-mediated gene regulation in plant-associated bacteria. Annual Review of Phytopathology 36:207-225.
Pierson III, L. S. and E. A. Pierson. 1996. Phenazine antibiotic production in Pseudomonas aureofaciens: role in rhizosphere ecology and pathogen suppression. FEMS Microbiology Letters 136:101-108.
Pierson, E. A. and D.M. Weller. 1994. The use of bacteria mixtures to improve the effectiveness of biological control of take-all of wheat. Phytopathology 84:940-947.
Selected Publications in Other Areas:
Fushi Wen, Ho Hyung Woo, Elizabeth A. Pierson, Toril D. Eldhuset, C. G. Fossdal, N. E. Nagy, and Martha C. Hawes. 2009. Synchronous Elicitation of Development in Root Caps Induces Transient Gene Expression Changes Common to Legume and Gymnosperm Species. Plant Molecular Biology Reporter 27(1):58-68.
Pierson, EA, JL Betancourt and RM Turner. Long-term studies of saguaro (Carnegiea gigantea) demography in the northern Sonoran Desert. (In preparation).
Harris, LK, EA Pierson, C Funicelli, WW Shaw, S Morales, K Hutton, and J Ashbeck. 2004. Long-term study of preserved and transplanted saguaros in an urban housing and golf course Development. Desert Plants 20: 33-43.
Bowers, J. E. and E. A. Pierson. 2001. Implications of seed size for seedling survival in Carnegiea gigantea and Ferocactus wislizeni (Cactaceae). The Southwestern Naturalist 46(3):272-281.
Pierson, E. A. and R. M. Turner. 1998. An 85-yr study of saguaro (Carnegiea gigantea) demography at the Desert Laboratory, Tumamoc Hill. Ecology 79:2676-2693.
Bowers, J. E., Webb, R. H., and Pierson, E. A., 1997, Primary succession of desert plants on debris-flow terraces, Grand Canyon, U.S.A. Journal of Arid Environments 36:67-86.