The Office of Biological and Environmental Research is an active participant
in the Interagency Working Group on Environmental Biotechnology (IWG – Environmental
Biotech.) This interagency working group operates under the auspices
of the Biotechnology Research Working Group (BRWG), Subcommittee on Biotechnology,
Committee on Science of the National Science and Technology Council (NSTC). Members
of the IWG – Environmental Biotechnology include DOE, the National
Science Foundation (NSF), the U.S. Environmental Protection Agency (EPA),
the Office of Naval Research (ONR) and the Strategic and Environmental
Research and Development Program (SERDP)
Over the past few years, the IWG – Environmental Biotechnology has
issued two solicitations for basic research in phytoremediation. The
focus of the program is on basic research projects that address the fundamental
mechanisms of interactions between plants, microorganisms, and contaminant
chemicals in soils, sediments and water (potentially marine, estuarine, or
freshwater systems) that result in the degradation, extraction, volatilization,
or stabilization of the contaminant. Contaminants of interest include organic
pollutants, radionuclides and metals.
Abstracts of currently funded projects
Genetic and Molecular Dissection of Arsenic Hyperaccumulation in the
Fern Pteris vittata. Jo Ann Banks, Purdue University
The goal of the proposed research is to identify the genes that are
necessary for arsenic hyperaccumulation in Pteris vittata using molecular
and genetic approaches. Specific objectives include: 1) identifying
P.
vittata genes that are involved in arsenic hyperaccumulation by
functional complementation in
S. cerevisiae, 2) using a genetics
approach to identify natural variants or mutations of
P. vittata genes
that negatively affect the plant's ability to tolerate or hyperaccumulate
arsenic, and 3) identifying and characterizing arsenic tolerant mutants
in
Ceratopteris richardii, a fern that is related to P. vittata
and is sensitive to arsenic. For objective 1, the function of
P.
vittata genes will be determined using a reverse genetics approach
recently developed for ferns, and then the appropriate genes will be
overexpressed in
Arabidopsis to see whether expression can confer
arsenic tolereance. For objective 2, a mutagenesis and genetic screening
approach will be used to identify the genes and mechanisms underlying
arsenic hyperaccumulation in
P. vittata. For objective 3, arsenic
resistant and accumulating
C. richardii ferns will be identified
and characterized to assist in providing genetic information on the
number and type of mutations needed to change an arsenic non-accumulator
into a hyperaccumulator.
DOE Project Officer: Paul E. Bayer
Project Period of Performance: Sept. 1, 2003 – Aug. 30, 2006
Project Award Total: $450,00
Key Words: phytoremediation, arsenic, ferns, Pteris vittata, genes, molecular
genetics, hyperaccumulation,
Arabidopsis,
Ceratopteris richardii
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Enhancement of Selenium Volatilization by Salicornia: Plant and Microbial
Interactions. Zhi-Qing Lin, Southern Illinois University
The proposed research aims to elucidate and manipulate the important environmental
and biological factors that limit the high production rates of volatile selenium
(Se). The following three hypotheses will be examined: 1) microbial volatilization
constitutes the most significant and effective pathway of Se removal in the
soil-
Salicornia system, 2)
Salicornia provides special microbial
habitats in support of the species-specific soil microbial populations with
accelerated ability for Se volatilization in the
Salicornia field,
and 3) phytotransformation of inorganic to organic Se and high availability
of organic Se from the decomposition of plant biomass are the key factors
facilitating the process of microbial Se production in a soil-plant system.
Specific objectives are: 1) to determine the respective contribution of
Salicornia plant
and soil microbes to the total Se volatilization in the soil-plant system,
2) to identify
Salicornia-associated microbial populations with accelerated
abilities for Se volatilization, and 3) to explore the interaction between
Salicornia and
associated microbes and the mechanisms underlying the enhancement of Se volatilization
in the
Salicornia phytoremediation system.
DOE Project Officer: Paul E. Bayer
Project Period of Performance: Sept. 1, 2003 – Aug. 30, 2006
Project Award Total: $81,951
Key Words: phytoremediation, selenium,
Salicornia, soil microbiology,
volatilization
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Pytoremediation Strategy for Arsenic. Richard B. Meagher, University of
Georgia
The proposed research will develop a genetics-based phytoremediation strategy
for arsenic removal that can be used in any plant species. The working hypothesis
is that organ-specific expression of genes controlling the transport, electrochemical
state, and binding of arsenic will result in the efficient extraction and
hyperaccummulation of arsenic into above ground plant tissues. The hypothesis
will be tested through the following research objectives: 1) enhance plant
resistance and expand sinks for arsenite by expressing elevated levels of
thiol-rich arsenic-binding peptides; 2) convert arsenate to arsenite in above
ground organs by expressing a bacterial arsenate reductase gene (ArsC) under
a light mediated leaf promoter; 3) characterize endogeneous root-specific
arsenic reductase (AtACR2) and enhance the transport of arsenate from roots
to shoots by suppressing the activity of the enzyme; 4) enhance arsenate
uptake via overexpression of high-affinity phosphate transporters; 5) enhance
intracellular transport of thiol-arsenate complexes into vacuoles in leaf
cells by elevating the expression of a glutathione conjugate pump in above
ground organs; and 6) combine these transgenic elements into test plants
(
Arabidopsis and tobacco) and demonstrate dramatic increases in arsenic
resistance and hyperaccumulation. The general approach will be to initiate
each experiment in
Arabidopsis and confirm the most informative experiments
in tobacco.
DOE Project Officer: Paul E. Bayer
Project Period of Performance: Sept. 1, 2003 – Aug. 30, 2006
Project Award Total: $450,000
Key Words: phytoremediation, arsenic, arsenate reductase,
Arabidopsis,
hyperaccumulation, molecular genetics
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Phytoremediation of Marine Sediments Contaminated with Polynuclear Aromatic
Hydrocarbons and Polychlorinated Biphenyls Using Eelgrass (Zostera marina). Michael
Huesemann, Pacific Northwest National Laboratory Marine Sciences Lab
The proposed research will examine the effects of eelgrass root zone aeration
on biodegradation of PAH’s and PCB’s. It is hypothesized that
eelgrass will increase photosynthesis-driven oxygen delivery to rhizosphere
microbes and will enhance aerobic degradation and increase the microbial
biomass and diversity. Using aquaria, the effects of eelgrass on the extent
of PAH/PCB removal will be studied as a function of sediment depth (and correlated
with root zone depth). In addition, microbial diversity and biomass will
be enumerated as both epiphytic and rhizosphere populations. Transfer of
PAHs/PCBs into the water column will be measured, as will uptake into eelgrass
tissues. The rate of oxygen release into the rhizosphere will be measured
over light and dark cycles to ascertain the role of photosynthesis. These
data will be used to semi-quantitatively identify the magnitude of eelgrass-enhanced
biodegradation of PAHs and PCB’s.
ONR Project Officer: Linda Chrisey; DOE Project Officer: Mr. Paul Bayer
Project Period of Performance: Oct. 15, 2003 – Oct. 14, 2007
Project Award Total: $493,926 (ONR) + $70,000 (DOE) = $563,926
Key Words:
Zostera marina, eelgrass, phytoremediation, marine sediments,
rhizosphere, polyaromatic hydrocarbons, polychlorinated biphenyls
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Mechanistic Role of Plant Root Exudates in the Phytoremediation of Persistent
Organic Pollutants. Jason White, MaryJane Incorvia Mattina, Martin Gent,
Barth Smets, Daniel Gage, Connecticut Agricultural Station, University of Connecticut
This proposal is designed to investigate the role of plant root exudates
in the phytoremediation of persistent organic pollutants in soil. Preliminary
data have shown that two weathered organic pollutants (p,p'-DDE, chlordane)
are readily translocated from soil to the tissues of certain plants. These
findings contradict a significant body of scientific evidence indicating
time-dependent reductions in contaminant availability in soil (i.e., sequestration).
We propose a novel mechanism of phytoremediation whereby plant root exudates
increase the bioavailability of weathered contaminants. The following hypotheses
will be tested: (1) The root exudates of certain plant species facilitate
the mobility and subsequent availability of weathered organic pollutants;
and (2) Contaminant solubilization by exudates occurs by direct or indirect
mechanisms. In direct enhancement, the exudate molecules directly induce
contaminant release from the soil. Possible mechanisms here include the formation
of exudate/contaminant complexes or the partial solubilization/reformation
of soil structure organic fractions through chelation of polyvalent metals
(iron and aluminum). A second hypothesis considers indirect enhancement,
where root exudates stimulate a microbial community that promotes contaminant
availability to the plant.
EPA Project Officer: Mitch Lasat
Project Period of Performance: Nov. 1, 2001 – Oct. 31, 2004
Project Award Total: $401,241
Key Words: phytoremediation, root exudates, organic pollutants, soil microbiology
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Evaluation of Monoterpene Producing Plants for Phytoremediation of PCB and
PAH Contaminated Soils. David Crowley, James Borneman, University of California-Riverside
Plants produce a variety of chemicals with structures that are analogous
to those of many commercially produced chemicals. Rhizodeposition of these
substances can beneficially affect xenobiotic degradation by promoting selective
enrichment of degrader organisms, enhancement of growth-linked metabolism,
and induction of genes for enzymes that facilitate cometabolism. In previous
research, we have exploited the ability of plant monoterpenes to induce bacteria
to cometabolize PCBs. Data from the literature and our prior research suggest
that terpenes produced in situ by plants also should be effective for promoting
degradation of many organic contaminants, including PAHs and other recalcitrant
contaminants. The objective of the proposed research is to evaluate monoterpene-producing
plant species for use in phytoremediation of PCBs and PAHs, and to investigate
the ecology of indigenous xenobiotic degrading bacteria in the rhizosphere
of monoterpene producing plants. Experiments will test four hypotheses: (1)
the rhizosphere selectively enriches for diverse populations of xenobiotic
degrading microorganisms that occur at higher population densities in the
rhizosphere as compared to the bulk soil; (2) plant and microbial substances
that are released into the rhizosphere enhance the expression and activity
of inducible enzymes that work in concert to degrade xenobiotic soil contaminants;
(3) monoterpene producing plants selectively enrich for diverse populations
of xenobiotic degrading microorganisms that will occur at higher population
densities in the rhizosphere as compared to the plants that do not produce
these substances; and (4) plant enhanced remediation of PAH and PCBs in the
rhizosphere can be enhanced by the addition of earthworms to improve soil
aeration for aerobic degradation processes.
EPA Project Officer: Mitch Lasat
Project Period of Performance: Nov. 1, 2001 – Oct. 31, 2004
Project Award Total: $393,135
Key Words: phytoremediation, biodegradation, rhizosphere, soil microbiology,
polycyclic aromatic hydrocarbons, polychlorinated biphenyls, monoterpenes
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Physiological Mechanisms of Estuarine Sediment Oxidation by Spartina Cordgrasses. Raymond
Lee, Washington State University
Cordgrasses of the genus
Spartina will be investigated for their potential
use as a phytoremediation tool in marine and estuarine sediments.
Spartina grasses
are adapted to saline, waterlogged sediments and exhibit vigorous growth,
forming dense monospecific stands in a variety of intertidal environments.
The capability of these plants to transport oxygen from the atmosphere to
the belowground rhizosphere has the potential to enhance microbial degradation
of organic pollutants, which can be limited by oxygen availability in anoxic
waterlogged soils. The specific objectives are as follows: (1) determine
rates of oxygen transport and release by
Spartina grasses; (2) identify
species and strains of
Spartina that have enhanced oxygen release
capabilities; (3) determine the mechanisms that facilitate oxygen transport,
and how transport is induced by environmental and hormonal signals. These
studies will assist in recovery of estuarine environments affected by pollution.
EPA Project Officer: Mitch Lasat
Project Period of Performance: Nov. 1, 2001 – Oct. 31, 2004
Project Award Total: $110,307
Key Words: phytoremediation, aquatic grasses,
Spartina, marine sediments,
rhizosphere
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The Molecular Basis for Heavy Metal Accumulation and Tolerance in the Hyperaccumulating
Plant Species, Thlaspi caerulescens. Leon V. Kochian, Cornell University
The goals of this research are to identify the basic mechanisms of heavy
metal hyperaccumulation in plants, and to isolate and characterize the suite
of genes that underly this hyperaccumulation trait in
Thlaspi caerulescens. Dr.
Kochian's group will use recent advances in plant molecular biology and genomics
to identify both metal transporter genes involved in metal accumulation and
tolerance, as well as genes involved in the production of low molecular weight
organic compounds (
e.g., peptides, organic genes, amino acids, metallothioneins,
phytochelatins) that can bind and detoxify Zn and Cd in plant cells. Based
on the recent sequencing and analysis of the
Arabidopsis genome, it
is now known that higher plants employ the same families of metal transporters
recently identified and characterized in yeast, bacteria and mammals for
metal accumulation and homeostasis. Dr. Kochian's group has cloned genes
in
T. caerulescens from these different metal transporter gene families
and will characterize these transporters to determine their role in metal
hyperaccumulation. This characterization will include determining in which
plant tissue and cell type different genes are expressed, the membrane localization
of transport proteins to help assign a potential role for each transporter,
and the elucidation of the physiological function of individual metal transporters.
They also are expressing
T. caerulescens genes in yeast to look for
genes conferring metal tolerance through the production of metal binding
organic ligands.
These approaches should allow the investigators to identify the suite
of genes that confer heavy metal hyperaccumulation in
T. caerulescens and
to elucidate the molecular mechanism(s) for this trait. The ultimate
goal of this research is to use these hyperaccumulation genes to develop
transgenic plants that both are metal hyperaccumulators and produce high
shoot biomass , and thus will be well suited for the phytoremediation
of metal contaminated soils.
NSF Program Manager: William E. Winner
Project Period: Sept. 1, 2001-Aug. 31, 2004
Award Total: $416,927
Key Words: phytoremediation, heavy metals,
Thlaspi, hyperaccumulator,
molecular genetics
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Genome-Wide Hunt For Metal Hyperaccumulation Genes. David E. Salt, Purdue
University
The overall objective of this project is to identify genes involved in metal
hyperaccumulation in metal-hyperaccumulating plants. These unique plant species
are able to accumulate between 0.1 and 3% of their shoot dry biomass as Cd,
Ni, Se or Zn depending on the species. Over 25% of the known hyperaccumulator
species are members of the
Brassicaceae family, and as such they are
related to Arabidopsis thaliana. By investigating the molecular genetics
of metal hyperaccumulation in species related to
A. thaliana, the
investigators will utilize the technical and genetic resources developed
during the
Arabidopsis genome project, harnessing powerful functional
genomics technologies to dissect metal hyperaccumulation at the genetic level.
Metal hyperaccumulators in the
Brassicaceae will be collected
from around the world, and genes important in hyperaccumulation will
be identified using three complementary approaches. Seeds from approximately
40 accessions of over 20 different species of hyperaccumulators in the
Brassicaceae family
will be collected from North America, France, Germany, Austria, Italy,
Greece and Turkey. Accessions of metal hyperaccumulators found to be
amenable to T-DNA insertional mutagenesis will be identified and over
100,000 genetic lines will be generated. In a forward genetic approach,
these lines will be screened for mutants exhibiting metal-sensitivity
and loss of metal-hyperaccumulation. T-DNA tagged genes from these mutants
will be isolated, and their role in metal hyperaccumulation determined.
In a reverse genetic approach, genomic DNA pools will be generated from
these lines and screened by PCR to identify lines containing T-DNA insertions
in genes already known or suspected to be involved in metal hyperaccumulation.
The
A. thaliana genome sequence will provide a rich source of
candidate genes for this reverse genetic approach. In a third approach,
cDNA expression libraries will be created in
E. coli and yeast
from hyperaccumulating species and screened for genes conferring heavy-metal
resistance and sensitivity. Taken together these approaches will provide
a comprehensive framework for the identification of genes involved in
metal hyperaccumulation in plants. The set of genes identified in this
project will provide a valuable resource for the future development of
plants ideally suited for the phytoremediation of metal polluted sites.
NSF Program Manager: William E. Winner
Project Period: Sept. 1, 2001 – Aug. 31, 2004
Award Amount: $450,000
Key Words: phytoremediation, metals, hyperaccumulator,
Arabidopsis, molecular
genetics
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Molecular Mechanism of Nickel Hyperaccumulation in Thlaspi goesingense. David
E. Salt, Purdue University
Intensive industrial and agricultural activity over the last 150 years has
imposed a large burden of heavy metals on the environment. Phytoextraction,
the use of plants for environmental cleanup of pollutants, including toxic
metals, from soils, holds the potential to allow the economic restoration
of these contaminated sites. For phytoextraction to be a viable alternative
to existing soil remediation strategies it will require the existence of
high biomass, rapidly growing metal-accumulating plants. Unfortunately, plants
do not exist at present that have all these desirable characteristics. There
are, however, a limited numbers of plants, collectively termed hyperaccumulators,
that grow on soils naturally enriched in various metals including Zn, Ni
and Se. These plants have the ability to naturally accumulate these metals
to between 0.1 and 3% of their shoot dry weight; this is at least 1000-fold
higher than most other plants. This unique ability makes these plants an
ideal starting point for the development of phytoextraction crops. One way
to develop such crops is to identify the genes responsible for metal accumulation
in these hyperaccumulator plants. Once identified and fully characterized
these genes could be transferred into high biomass, rapidly-growing plants
to generate crops ideally suited for phytoremediation. This grant will fund
the identification of such "metal hyperaccumulation" genes from
the nickel hyperaccumulator Thlaspi goesingense. Once identified, the usefulness
of these genes for phytoremediation will be rapidly assessed by their transfer
to
Arabidopsis thaliana, a convenient model plant. Genes identified
for enhanced metal tolerance and accumulation in this model plant will then
be selected for transfer to plants more suited to phytoremediation applications.
NSF Program Manager: Stephen Herbert
Project Period: April 15, 2001 - May 31, 2004
Award Amount: $329,806
Key Words: phytoremediation, phytoextraction, metals, hyperaccumulator,
Thlaspi,
molecular genetics
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Intraspecific Variation in Thlaspi caerulescens: The Key to Increasing
Metal Sequestration in Plants . Stephen D. Ebbs, Southern Illinois University
Carbondale
Metal hyperaccumulation and hypertolerance are unique traits observed in
a limited variety of plant species from around the world. A relatively understudied
aspect with respect to metal hyperaccumulating plant species is the natural
variation in hyperaccumulation and tolerance observed between populations
within a species (i.e., intraspecific variation). For example, recent studies
have shown marked differences in the hyperaccumulation of Cd and Zn across
populations of
Thlaspi caerulescens. The inherent variability in hyperaccumulation
displayed by
T. caerulescens and the unique cellular and subcellular
patterns of metal distribution (
e.g., epidermal and vacuolar sequestration)
in leaves provide a natural model system in which to examine the leaf-level
mechanisms that control metal homeostasis. Understanding the basis of this
variation will contribute to the ongoing efforts to develop more efficient
hyperaccumulators for metal phytoremediation and metal "bio-mining".
To examine these leaf-level mechanisms, this project will (1) use cell viability
assays to compare the metal tolerance of leaf mesophyll cells from different
populations of
T. caerulescens to determine the contribution of these
cells to the intraspecific variation in metal hyperaccumulation; (2) conduct
radiotracer transport studies with isolated vacuoles and/or vacuole membranes
from different populations to determine whether intraspecific variation in
the rate or extent of vacuolar sequestration contributes to hyperaccumulation;
and (3) use 2-D protein gel electrophoresis to determine if the more efficient
metal-accumulating plant populations possess novel proteins that contribute
to their ability to tolerate and sequester metals in leaves. Together the
results of this study will add to our understanding of the relationship between
metal distribution in leaves and the extent to which different populations
of
T. caerulescens hyperaccumulate Cd and Zn. This unique insight
into the metal dynamics in leaves will be instrumental in the development
of higher biomass plants for phytoremediation.
NSF Program Manager: William E. Winner
Project Period: Oct. 1, 2003 – Sept. 30, 2004
Award Amount: $100,000
Key Words:phytoremediation, metals, hyperaccumlator,
Thlaspi, molecular
biology
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Are Plant Root-Mycobacterium Interactions Beneficial in Remediation of Polyaromatic
Hydrocarbons? Anne J. Anderson, Utah State University
PAH-contaminated soils pose environmental and health hazards. Phytoremediation
is a cost effective method for on-site clean-up. It is well suited for large
surface areas such as those designated as “brownfields” within
urban settings or sites where soil excavation and removal is difficult. This
proposal focuses on understanding more of the ecology of mycobacteria that
have PAH-degrading potential. Currently there is little knowledge of how
such mycobacteria interact with plant roots and whether this association
has positive impacts on the metabolism of the plant and/or the microbe to
promote bioremediation. The hypotheses to be tested are: 1) The presence
of roots colonized by PAH-degrading mycobacteria improves the bioavailability
of a model, recalcitrant PAH, pyrene; 2) The mineralization of pyrene is
enhanced by the interaction of the roots with the mycobacteria; 3) Colonization
of the root requires discrete interactions between the mycobacteria and root
surface; 4) Colonization of the root permits the expression of the gene in
mycobacteria encoding the first enzyme involved in PAH degradation, dioxygenase;
5) Root phenoloxidases, which may participate in PAH-remodeling, are changed
in activity in the roots colonized by mycobacteria.
NSF Program Manager: William E. Winner
Project Period: October 1, 2003 - September 30, 2006
Award Amount: $398,336
Key Words: phytoremediation, plant-microbe interactions, polyaromatic hydrocarbons,
mycobacteria
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Molecular Genetics of Polycyclic Aromatic Hydrocarbon Stress Responses and
Remediation by Arabidopsis thaliana. Adan Colon-Carmona, University
of Massachusetts Boston
The proposed project explores the underlying molecular mechanisms for polycyclic
aromatic hydrocarbon (PAH)-induced responses in plants, as well as their
potential biodegradation pathways. PAHs are organic pollutants that cause
human health problems such as cancer. PAHs are contaminants resulting from
oil-based manufacturing. Some plant species, including crop plants such as
sunflower, soybean, pea and carrot, can grow on moderate levels of crude
oil-contaminated soil. Yet, very little is known at the molecular level about
the mechanisms of PAH uptake and degradation, or even cell signaling pathways
regulating PAH stress responses. A better understanding of PAH stress physiology
will lead to the generation of phytoremediation strategies in pollution clean-up
and biomonitoring. The aims of this proposal are the following: 1) to characterized
the physiological responses to PAHs in
Arabidopsis thaliana, 2) to
identify the signaling pathways that mediate the various PAH-induced plant
responses, 3) to screen genetically mutagenized populations for plants that
are defective in PAH-induced growth responses, and 4) to identify, through
bacterial screens, plant cDNAs that can be used in PAH degradation. The long
term goal of these studies are to utilize the information regarding PAH-induced
responses in
Arabidopsis to engineer trees or crop plants with extensive
root systems for their use in biodegradation and biomonitoring of PAH contamination.
NSF Program Manager: William E. Winner
Project Period: Sept. 1, 2003 – Aug. 31, 2006
Award Amount: $340,000
Key Words: phytoremediation, polyaromatic hydrocarbons,
Arabidopsis, molecular
genetics
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Understanding and Enhancement of Arsenic Hyperaccumulation by a Fern Plant. Jean-Francois
Gaillard, Northwestern University and Lena Q. Ma, University of Florida
The objective of this research is to understand the mechanisms of arsenic
uptake, translocation, distribution and detoxification by Brake fern. The
efficiency of arsenic uptake by Brake fern suggests the cost-effective use
of this plant for the remediation of arsenic contaminated soils. This research
focuses on elemental interactions of arsenic with calcium and phosphorus,
plant biochemical responses under arsenic stresses, speciation and characterization
of arsenic in the plant using analytical, microscopic and spectroscopic techniques,
and microbe-root-plant-arsenic interactions. Arsenic hyperaccumulation characteristics
in Brake fern growing in soils of different arsenic concentrations will be
investigated using arsenic spiked soils. The impacts of P (increases arsenic
availability yet competes with arsenic uptake) and Ca (increases plant arsenic
uptake and translocation) on arsenic accumulation, and biochemical responses
of Brake fern to elevated arsenic (detoxification) will be examined. Also,
the beneficial effects of mycorrhizal fungi for enhancing arsenic accumulation
by Brake fern will be explored. This is a collaborative research project
between the University of Florida and Northwestern University.
NSF Program Manager: Nicholas Clesceri
Project Period: Sept. 1, 2001 – Aug. 31, 2004
Award Amount: $376,672
Award Amount: $358,000
Key Words: phytoremediation, arsenic, Brake fern, hyperaccumulator
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Applications of 13 C tracer studies and stable isotope geochemistry
to determine rhizosphere alteration of PAH bioavailability in contaminated geomedia. Dr.
Elizabeth G. Nichols, North Carolina State University.
This proposal uses polycyclic aromatic hydrocarbons (PAHs) as model contaminants
to delineate how the rhizospheres of plant systems impact weathered contaminant
sequestration and bioavailability. We propose to use two isotopic tracer
approaches in which 13 CO2 photosynthetic labeled plant exudates or uniformly
labeled 13 C-PAHs are introduced into weathered PAH contaminated media vegetated
with Phragmites australis. Three field sites will be used to provide PAH
weathered geomedia. We will determine if organic matter composition in geomedia
fractions from the rhizosphere zone differs from non-rhizosphere geomedia
over time and if compositional differences alter PAH partitioning, desorption,
and toxicity in specific fractions such as particulate fractions and diagenetic
fractions such as black carbon and humic materials.
NSF Project Officer: Thomas Waite
Project Period of Performance: Sept. 1, 2003 – Aug. 31, 2006
Project Award Total: $434,103
Key Words: phytoremediation, rhizosphere, PAH
Involvement of an endosymbiotic Methylobacterium sp. in the biodegradation
of explosive RDX and HMX inside poplar tree (Populus deltoides). Dr.
Jerald Schnoor, University of Iowa
The main objective of the proposed research is to investigate the involvement
of endophytic pink pigmented facultative methylotrophic (PPFM) bacteria in the
bioremediation of the RDX and HMX inside poplar trees. A secondary objective
is to characterize the symbiotic plant-bacteria relationship and the extent of
poplar contamination by PPFM bacteria. The hypothesis is that endosymbiotic microbes,
such as PPFM, living inside woody plants are involved in and can improve significantly
phytoremediation of organic pollutants. Enhanced biodegradation originates either
directly from bacterial metabolism or from an improved plant metabolism due to
symbiotic association with the bacteria.
NSF Project Officer: Thomas Waite
Project Period of Performance: Sept. 1, 2003 – Aug. 31, 2006
Project Award Total: $247,441
Key Words: phytoremediation, RDX, HMX,
Populus, endosymbionts, methylotrophs
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