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Agricultural Research Service United States Department of Agriculture
 
Thecan Caesar

Research Microbiologist

TheCan Caesar.TheCan Caesar-TonThat


Phone: 406.433.9415
Fax: 406.433.5038
 
 
 
• Education • Current Research • Research Experience • Related Web Pages • Publications • 

 

 

 

 

Additional Pages: Research Projects,* Publications*
*Taken from the Agricultural Research Information System (ARIS) database.


 
 

 

EDUCATION

 
M.S. Microbiology 1974 University of Geneva, Switzerland
Ph. D. Microbiology 1979 University of Geneva, Switzerland

 


CURRENT RESEARCH

 

NATIONAL PROGRAM 202: SOIL RESOURCE MANAGEMENT

Dryland soils of the Northern Plains have lost, on average 50% of their original organic matter due to excessive tillage and summer fallow. The decline in organic matter is accompanied by structural deterioration of soils (decrease of soil aggregation), reduced water infiltration, poor oxygenation, and increased erosion. To evaluate sustainability of agricultural management practices, the assessment of soil health using various indicators of soil is needed. The goals of Dr. Caesar are to evaluate the interactions between soil management and soil biota, in particular the effects of soil disturbance (till versus no till management practices) and crop residues on specific saprophytic basidiomycete fungi that can aggregate soil, forming water stable aggregates. She develops knowledge and techniques for sustainable soil and crop management that emphasizes preservation and enhancement of these specific fungi for the benefit of soil structure. The work identifies the need to inquiring not only about relation to the mechanisms by which these fungi stabilize soil but also to the wider problems of understanding the importance of this class of fungi and their role in different litter resource ecosystems.

 

NATIONAL PROGRAM 207: INTEGRATED FARMING SYSTEMS

Control of leaf spot disease of sugar beets (b vulgaris L.) caused by Cercospora beticola has relied mostly on chemical control.  Severe disease incidences result in significant yield losses and reduced sugar content of beets as well as expensive applications of pesticides.

C. beticola Sacc. has been shown to produce cercosporin, a deep red colored, light activated polyketide toxin on a wide range of organisms such as other fungi, bacteria, plants and animals.  Cercosporin has since been isolated from a large number of Cercospora species and from Cercospora infected-plants.  In a biological approach, Dr. Caesar, in collaboration with Dr. R. T. Lartey (ARS, Sidney, MT), investigates the mechanisms of degradation and detoxification of cercosporin by laccase, a ligninolytic enzyme sectreted by antagonistic basidiomycete fungi.  Degradation of the toxin by laccase will prevent break down of plant cell membranes by cercosporin resulting in starvation of Cercospora.

 

 

 

RESEARCH EXPERIENCE

 

After completing her Doctorate of Science (Ph.D.) in 1979 at the University of Geneva, Switzerland, she was hired as a research microbiologist at the Department of Microbiology in Geneva, Switzerland to conduct research on cellular mechanisms of the fungus Neurospora crassa in response to heat shock. She demonstrated at the ultrastructural level that the gene translation process is curtailed in heat-treated fungal cells. In 1983, she was awarded a competitive grant from the Swiss Foundation of Science to spend two years at the Department of Plant Pathology at Cornell University working in the laboratory of Dr. H.C. Hoch studying clathrin coated vesicles from filamentous fungi (Neurospora crassa and Uromyces phaseoli). She also used Neurospora crassa to study the mechanisms by which the fungicide benomyl alters membrane b-tubulin affecting linear growth. In 1986, she moved to the Department of Plant Pathology, at the University of California-Berkeley, for a research scientist position working on mechanisms of adhesion for fungi. Then she moved to Bozeman, Montana, where she accepted an assistant research professor position at Montana State University in the Department of Microbiology in collaboration with Dr. Joan M. Henson. They investigated the role of fungal melanin in bioremediation. This research provided direct evidence that copper stimulates melanin production and that melanin plays an important role in copper sequestration by forming insoluble metal sulfides that can be trapped in cell walls. This data helped to explain why copper-based fungicides failed to control diseases caused by Gaeumannomyces graminis var. graminis and thus provides important knowledge for the development of effective control strategies for this pathogen. She also studied in collaboration with Dr. Jim E. Cutler on the effects of monoclonal antibody (Mab B6.1) to the human pathogen Candida albicans on protection of candidiasis in comparison with the effects of the non-protective Mab B6 for ability to support neutrophil (polymorphonuclear leukocyte [PMN]) candidacidal activity.
  

 

 

RELATED WEB PAGES

 

Agricultural Systems Research Unit Projects

Enzyme May Protect Sugar Beets From Leaf Spot Disease (.PDF)

 

 

 

SELECTED PUBLICATIONS:
Please note: The most recent publications by this scientist may not yet be listed here. Please check the ARIS "Publications" page for possible new titles.

  • Busscher, W., Novak, J., and Caesar, T. 2006. Organic Matter and Polyacrylamide Amendment of Norfolk Loamy Sand. Soil & Tillage Research Journal.

  • Novak, J., Szogi, A., Watts, D., Basta, N., Dayton, E., and Caesar, T. 2006. Use of Water Treatment Residuals As a Best Management Practice to Bind P in Upland and Wetland Ecosystems. Abstract, International Soil Science Congress Proceedings.

  • Sainju, U.M., Lenssen, A.W., Caesar, T., Waddell, J.T. 2006. Tillage and Crop Rotation Effects on Dryland Soil and Residue Carbon and Nitrogen. Soil Science Society of America Journal. 70:668-678.

  • Sainju, U.M., Lenssen, A.W., Caesar, T., Waddell, J.T. 2006. Tillage and Crop Rotation Effects on Dryland Soil and Residue Carbon and Nitrogen. Soil Science Society of America Journal. 70:668-678.

  • Sainju, U.M., Lenssen, A.W., Caesar, T., and Waddell, J.T. 2006. Carbon Sequestration in Dryland Soils and Plant Residue as Influenced by Tillage and Crop Rotation. Journal of Environmental Quality. 35:1341-1347. (PDF; 191 KB)

  • Sainju, U., Lenssen, A., Evans, R., Caesar, T., and Waddell, J. 2005. Tillage, Crop Rotations, and Cultural Practices Effects on Dryland Soil and Crop Residue Carbon and Nitrogen. Abstract, International Conference on Sustainable Agriculture for Food, Energy and Industry.

  • Lartey, R.T., Caesar, T., Caesar, A.J., Shelver, W.L., Sol, N.I., Bergman, J.W. 2005. Safflower: a New Host of Cercospora Beticola. Plant Disease. 89(8):797-801.

  • Lartey, R.T., Caesar, T., Sol, N.I., Goshroy, S. 2005. Additional Evidence of Safflower (Carthamus Tinctorius) As An Alternate Host to Cercospora Beticola. In: Proceedings from the 33rd Biennial Meeting Agriculture. American Society of Sugarbeet Technologists, March 2-5, 2005, Palm Springs, California. P. 144-150.

  • Wuest, S.B., Caesar-Tonthat, T.C., Wright, S.F., Williams, J.D. 2005. Organic Matter Addition, N, and Residue Burning Effects on Infiltration, Biological, and Physical Properties of An Intensively Tilled Silt-Loam Soil. Soil & Tillage Research 84 (2005) 154-167.

  • Pikul Jr, J.L., Johnson, J.M., Wright, S.E., Caesar, T., Ellsbury, M.M. 2005. Soil Organic Matter and Aggregate Stability Affected by Tillage. E.A. Ghabbour and G. Davies (Eds) Humic Substances: Molecular Details and Applications in Land and Water Conservation. Taylor and Francis, Inc. New York. P. 243-258.

  • Caesar, T., Caesar, A., and Sainju, U. 2004. Isolation, Identification, and Characterization of Soil Aggregating Bacteria in Soil Microaggregates. Abstracts, American Society of Agronomy Meetings.

  • Lartey, R.T., Caesar, T., Caesar, A.J., Shelver, W.L., Sol, N.I. 2004. Safflower: An Alternate Host of Cercospora Beticola. Phytopathology. 94(6):s57.

  • Pikul Jr, J.L., Wright, S.E., Johnson, J.M., Caesar, T., Ellsbury, M.M. 2003. Tillage Effects on Distribution of Organic Matter among Soil Aggregate CLASSES.[CD-ROM]. Asa-Cssa-Sssa Annual Meeting Abstracts. Madison, Wisconsin.

  • Pikul Jr, J.L., Johnson, J.M., Caesar, T., Wright, S.E., Ellsbury, M.M. Soil Organic Matter and Aggregate Stability Affected by Tillage in the Northern Corn Belt. Natural Organic Matter in Soils and Water North Central Region Symposium. 2003. P. 20.

  • Lartey, R.T., Weiland, J.J., Caesar, T., Bucklin Comiskey, S.A. a Pcr Protocol for Rapid Detection of Cercospora Beticola in Infected Sugar Beet Tissues. Journal of Sugarbeet Research. 2003. V. 40 P. 1-10.

  • Holtz, B. A., McKenry, M. V., and Caesar-TonThat, T. C. Wood chipping almond brush and its effect on soil and petiole nutrients, soil aggregation, water infiltration and nematode and basidiomycete populations. Mediterranean Options (in press).

  • Lartey, R. T., Weiland, J. J., Caesar-TonThat, T. C., and Bucklin-Comiskey, S. A. 2003. A PCR protocol for rapid detection of Cercospora beticola in injected plant tissues. Journal of Sugar Beet Research 49:1-2.

  • Holtz, B.A., McKenry, M.V., and Caesar-TonThat, T. C. 2002.  Wood chipping almond brush and its effect on the almond rhizosphere, soil aggregation, and soil nutrients.  Acta Horticulture (in press).

  • Caesar-TonThat, T. C. 2002. Soil binding properties of mucilage produced by a basidiomycete fungus in a model system. Mycological Research 106:930-937.

  • Cochran V. L. and Caesar-TonThat, T. C. 2001. Soil quality factors and grain yields 16 years after top soil removal. (Submitted paper).

  • Caesar-TonThat, T. C., W. Shelver, R. G. Thorn, and V. L. Cochran, 2001. Generation of antibodies for soil-aggregating basidiomycete detection to determine soil quality. Applied Soil Ecology 18:99-116.

  • Caesar-TonThat, T. C., and V. L. Cochran. 2001. Role of saprophytic basidiomycete soil fungus in aggregate stability, p. 575-579. In: D. E. Stott, R. H. Mohtar, and G. C. Steinhardt (eds). Sustaining the Global Farm- Selected papers from the 10th International Soil Conservation Organization Meeting, May 24-29, 1999, West Lafayette, IN.

  • Caesar-TonThat, T. C., and V. L. Cochran. 2000. Soil aggregate stabilization by a saprophytic lignin decomposing basidiomycete fungus. I. Microbiological aspects. Biology and Fertility of Soils 32:374-380.

  • Frederick, B., T. C. Caesar-TonThat, M. H. Wheeler, K. B. Sheehan, W. A. Edens and J. M. Henson. 1999. Isolation and characterization of Gaeumannomyces graminis var. graminis melanin mutants. Mycological Research 103:99-110.

  • Money, N. P., B. Frederick, T. C. Caesar-TonThat, and J. M. Henson. 1998. Melanin synthesis is associated with changes in hyphopodia turgo, permeability, and wall rigidity in Gaeumannomyces graminis var. graminis. Fungal Genetics Biology 24:240-251.

  • Caesar-TonThat, T. C., and J. E. Cutler. 1997. Enhancement of mouse neutrophil candidacidal activity by a protective monoclonal antibody. Infection Immunity 65:5354-5357.

  • Henson, J. M., and T. C. Caesar-TonThat. 1995. Mitochondrial plasmids of Gaeumannomyces-Phialophora fungi and their detection by primed, in situ fluorescent labelling. Experimental Mycology 19:263-274.

  • Caesar-TonThat, T. C., F. Van Ommen Kloeke, G. G. Geesey, and J. M. Henson. 1995. Melanin production by a filamentous soil fungi in response to copper and localization of copper sulfide by sulfide-silver staining. Applied and Environmental Microbiology 61:1968-1975.

  • Caesar-TonThat, and D. C. Sands. 1994. Oil and absorbent coated granules containing encapsulated living organisms for controlling agricultural pests. US Patent number: 5,358,863.

  • Caesar-TonThat, T. C., W. E. Dyer, P. C. Quimby, and S. S. Rosenthal. 1993. Formulation of an endoparasitic nematode Subanguina picridis Brzeski, a biocontrol agent for Russian knapweed (Acroptilon repens (L.) (DC). Biological Control 5:262-266. Quimby, Jr. P. C., J. L. Birdsall, A. J. Caesar, W. J. Connick Jr., C. D. Boyette, T. C.

  • Liebman, J. A., T. C. Caesar-TonThat, and L. Epstein. 1993. Ultrastructure of Cochliobolus victoriae conidia incubated on fungistatic soil. Mycological Research 97:1419-1429.

  • Turian, G., F. Barja, and T. C. Caesar-TonThat . 1992. Nucleolar dense granules in cytochalasin-treated conidia of Neurospora crassa. Cell Biology International Reports. 16:1265-1266.

  • Caesar-TonThat, T. C., W. E. Dyer, S. S. Rosenthal, P. C. Quimby, and S. W. Chaney. 1992. Cooperative research efforts to develop the use of a nematode for Russian knapweed biocontrol. The Georges Wright Forum 9 (1):45-48.

  • Caesar-TonThat, T. C., and L. Epstein. 1990. Freeze-substituted fungal cells of Nectria haematococca: a comparison of the macroconidial walls of the adhesion-competent wild-type with an adhesion-reduced mutant. Experimental Mycology 15:193-205.

  • Caesar-TonThat, T. C., C. Rossier, F. Barja, G. Turian, and U. P. Roos. 1988. Induction of multiple germ tubes in Neurospora crassa by antitubulin agents. European Journal of Cell Biology 46:68-79.

  • Caesar-TonThat, T. C., K. Hoang Van, G. Turian, and H. C. Hoch. 1987. Isolation and characterization of coated vesicles from filamentous fungi. European Journal of Cell Biology 43:189-194.

  • Turian, G., and T. C. Caesar-TonThat. 1987. Multipolar germination of conditionally produced conidia in an "amycelial" mutant of Neurospora crassa. Journal General Applied Microbiology 33:543-545.

  • Turian, G., T. C. TonThat, and R. Ortega-Perez. 1985. Acid tip linear growth in fungi: requirements for H+/Ca2+ inverse gradients in cytoskeleton integrity. Botanica Helvetica 95:311-322.

  • Turian, G., C.-L. Geisler, and T. C. TonThat . 1985. Ribosomal exclusion from the most acidic tip-zone of fungal hyphae. Microbios Letters 30:19-22.

  • TonThat, T. C., and G. Turian. 1984. High-resolution autoradiography of nuclear modifications during and after heat induction of microcyclic conidiation in Neurospora crassa. Protoplasma 120:165-171.

  • TonThat, T. C., M. Michea-Hamzehpour, and G. Turian. 1983. Ultrastuctural demonstration of loss and recovery of cytochrome oxidase activity during and after heat-induction of microcyclic conidiation in Neurospora crassa. Protoplasma 116:149-154.

  • TonThat, T. C., G. Turian, J. Fakan, and A. Gautier. 1981. Ultrastructural cytochemistry of perinucleolar dense spots in heat-treated macroconidia of Neurospora crassa. European Journal of Cell Biology 24:317-319.

  • Michea-Hamzehpour, M., F. Grange, T. C. TonThat, and G. Turian. 1980. Heat-induced changes in respiratory pathway and mitochondrial structure during microcyclic conidiation. Archives Microbiology 125:53-58.

  • Michea-Hamzehpour, M., R. Ortega-Perez, A. Rougemont, F. Vanderhaeghe, E. Khandjian, T. C. TonThat, and G. Turian. 1979. Isolation of two mitochondrial populations with differential hydroxamate sensitivity from the poky mutant of Neurospora crassa. FEMS Microbiology Letters 6:213-218.

  • TonThat, T. C., and G. Turian. 1978. Ultrastructural study of microcyclic macroconidiation in Neurospora crassa. Archives Microbiology 125:53-58.

  • Rossier, C., T. C. TonThat, and G. Turian. 1977. Microcyclic conidiation in Neurospora crassa. Experimental Mycology 1:52-62.

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Last Modified: 09/26/2008