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CONTACT INFORMATION
Research Microbiologist
Phone: 406.433.9415
Fax: 406.433.5038
E-mail: caesart[at]sidney.ars.usda.gov
EDUCATION
M.S. Microbiology 1974
University of Geneva, Switzerland
Ph. D. Microbiology 1979
University of Geneva, Switzerland |
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CURRENT RESEARCH |
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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. |
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RESEARCH EXPERIENCE |
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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.
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RELATED WEBPAGES |
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 Biological Control of Cercospora Leaf Spot of
Sugar Beets
Enzyme May Protect Sugar Beets From Leaf
Spot Disease (.pdf)
Hydrophobicity of
Basidiomycetes as a Factor in Soil Structure
Managing to Improve Soil Quality
Molecular Tools for
Bio Control, Soil Quality, and Insect Research
Plant
Pathogen/Insect Synergisms are the Key to the Bio Control of Rangeland
Weeds
Russuloid
Basidiomycete Fungi as Bio Indicators for Soil Quality |
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SELECTED PUBLICATIONS |
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Rossier, C., T. C.
TonThat, and G. Turian. 1977. Microcyclic conidiation in
Neurospora crassa. Experimental Mycology 1:52-62.
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TonThat, T. C., and
G. Turian. 1978. Ultrastructural study of microcyclic macroconidiation
in Neurospora crassa. Archives Microbiology 125:53-58.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Cochran V. L. and
Caesar-TonThat, T. C. 2001. Soil quality factors and grain yields
16 years after top soil removal. (Submitted paper).
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Caesar-TonThat, T. C.
2002. Soil binding properties of mucilage produced by a
basidiomycete fungus in a model system. Mycological Research
106:930-937.
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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).
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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.
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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).
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CONTACT INFORMATION
Biological Science Technician
Phone: 406.433.9433
Fax: 406.433.5038
E-mail: lsolberg[at]sidney.ars.usda.gov
EDUCATION
B.S. Range Management
- 1975 - North Dakota State
University
M.S. Range Ecosystems
- 1977 - South Dakota State
University
Ph.D. Agronomy with
emphasis in protein biochemistry and plant physiology - 1992 - South
Dakota State University |
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USDA-ARS-NPARL
P.O. Box 463 Sidney, MT 59270 PH: 406.433.2020 FAX: 406.433.5038
For accessibility
questions or other concerns, please e-mail: webmaster[at]sidney.ars.usda.gov
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