Fiscal
Year 2002 Awards
Microbial Postdoctoral Research Fellowships
Fellow’s Name Host Institution Research Area/Training Plan NSF Award #
Title of Research & Training Plan
Abstract
Anne E. Arnold
Duke University
Systematic Biology 0200413
"Diversity
of fungi within living leaves: molecular insights into ecology and evolution of
endophytic fungi in leaves of tropical trees."
Fungal endophytes,
fungi inhabiting plants without causing disease, are highly diverse in tropical
trees, yet are poorly known. This research assesses tropical endophyte
diversity using (a) traditional isolations and multilocus sequencing and (b)
direct amplification of endophyte DNA from leaves. Its overall goal is to
integrate endophytes into the broader fungal phylogeny and explore the
evolution of fungus-photobiont associations.
Anne E. Bernhard
University of Washington
Metabolic Biochemistry 0200512
"Measuring
activity and diversity of ammonia-oxidizing bacteria in estuarine
sediments."
This research
focuses on ammonia-oxidizing bacteria as a model system to study the relationship between microbial diversity
and community processes in estuarine sediments. It employs real-time reverse
transcription polymerase chain reaction (PCR) to measure changes in the
expression of the enzyme responsible for ammonia oxidation, that is, ammonia
monooxygenase (AMO).
Jennifer A. Bieszke
Michigan State University Cell Biology 0200228
"Role
of histone deacetylases in the virulence of a plant pathogenic fungus."
Histone deacetylases (HDACs) are important regulators of many cellular
processes. Four HDAC genes have been identified in the maize pathogen,
Cochliobolus carbonum, and one of them has been shown to be important for
virulence. Biochemical, immunological, and genetic techniques are being used to
study the role of these HDACs in development and pathogenicity.
Alison Buchan
Yale University Metabolic
Biochemistry 0200164
"Retrieving
novel bacterial genes involved in aromatic compound degradation from natural
environments using Acinetobacter as a host."
Many naturally
occurring aromatic compounds are broken down by microbes via the
beta-ketoadipate pathway. This research manipulates the genetic system of a
naturally transformable soil bacterium and uses it as a vehicle for
understanding the versatility and diversity of this ecologically important
pathway in uncultivated natural bacterial assemblages.
Sherry L. Dollhopf
Florida State University
Ecology 0200203
"The
microbiology of iron reduction in the salt marsh."
This research is
investigating the importance of microorganisms that use iron to obtain energy
for growth in the salt marsh ecosystem. Comprehensive geochemical and
microbiological laboratory techniques are being used to quantify the
contribution of microbial iron respiration to total organic matter decomposition
in different salt marsh environments to estimate the importance of iron
respiration to carbon cycling on a marsh-wide scale. The diversity and
community structure of iron-reducing microorganisms is being investigated using
serial dilution cultures, 16S rRNA based techniques, fluorescent in situ
hybridization, and microscopy. This research could lead to the discovery of new
iron-reducing organisms that are important in coastal marine environments.
Melinda Duplessis
University of Washington Evol
& Ecol Physiology 0200104
"Chloroplast
gene experssion studies on the toxic bloom-forming organism Heterosigma
akashiwo during resting cell formation and activation."
Massive blooms of
the toxic golden-brown alga Heterosigma akashiwo negatively impact all levels
of the food web. It can form a resting stage that allows it to withstand
stressful environmental conditions. This research examines chloroplast genes
involved in environmental recognition and the regulatory processes that enable
Heterosigma to enter and escape dormancy.
Katherine E. Gibson
Stanford University Cell Biology 0200482
"Symbiotic regulation and function of proteins in Sinorhizobium melilota Outer Membrane."
Sinorhizobium
melilota, a gram negative bacterium, and the legume Medicago truncatula are
partners in a symbiosis that requires coordinated differentiation for
productive nodulation. This research seeks to identify bacterial outer membrane
proteins (OMPs) differentially expressed in plant-associated bacteroids
compared to free-living bacteria, to be followed by a genetic and physiological
analyses of the role these proteins play at the interface of the bacterium and
plant. This will enhance our understanding of the complex metabolic coupling
between bacteria and plant required for nitrogen fixation.
David E. Graham
Virginia Tech University Biochemistry 0200122
"Biosynthesis
of two coenzymes in methanogenic microorganisms."
The methanogenic microorganism Methanococcus jannaschii grows in hydrothermal vents, using hydrogen and carbon dioxide to make methane gas. This project seeks to identify how M. jannaschii produces two coenzymes, Coenzyme M and Coenzyme B, which cooperate in the final steps of methanogenesis to release methane and conserve energy for the cell.
Christine V. Hawkes University of California-Berkeley Ecology 0200720
"Effects of plant roots, mycorrhizal fungi, and rhizosphere bacteria on soil carbon cycling."
The aim of this research
is to elucidate how interactions among plants, arbuscular mycorrhizae, and
rhizosphere bacteria affect carbon cycling both locally and at the ecosystem
level. This requires a combination of DNA-based microbial community
characterization, engineered bacterial reporter gene systems to detect specific
carbon compounds, traditional isotope techniques and 13C PLFA for following the
flow and fate of carbon, and an experimental design incorporating different
rhizosphere communities from congeneric native and introduced plant species in
CA and the UK. The results of this work will add to our understanding of
microbial interactions in the rhizosphere and their consequences, improve our
ability to predict system-level responses to global change, and add to our
capacity to manage biological invasions.
Jason D. Hoeksema U
California-Santa Cruz Ecol & Evol
Physiology 0200129
"Does
coniferous forest plant community composition
influence the evolution of host specificity in mycorrhizal fungi?
We have little understanding of spatio-temporal variation in the
interactions of mycorrhizal fungi with their host plants. This research
investigates the impact of large-scale variation in plant community composition
in the Pacific Northwest on the evolution of host specificity of
ectomycorrhizal fungi in the genus Rhizopogon.
Nicole T. Liberati-Moore
Massachusetts General Hospital
Cell Biology 0200718
"Pseudomonas
aeruginosa Multi-Host Virulence."
Using a novel
system of invertebrate hosts to rapidly identify Pseudomonas aeruginosa genes
that confer virulence, significant overlap in the genes required for
pathogenesis in both invertebrate and mammalian hosts has been discovered,
suggesting that the mechanisms that direct pathogenesis are common among the
many hosts of P. aeruginosa. To dissect the molecular events of pathogenesis
the role of the fatty acid biosynthesis gene, fabF, a gene isolated by
multi-host screening, is being examined. Novel virulence factors are also being
identified using a library of non-redundant mutants with a disruption in every
non-essential open reading frame in the P. aeruginosa genome. The defined
nature of this library allows exhaustive screening for all genes required for
P. aeruginosa pathogenesis. Such analyses will provide a comprehensive view of
the universal mechanisms employed by P. aeruginosa to infect its many hosts.
Timothy I. McLean
University of Southern California
Genetics 0200212
"Molecular
analysis to identify genes that contribute to the
establishment and maintenance of a protistan symbiosis."
Little is known at
the molecular level about the mechanisms underlying symbiotic associations.
This project seeks to identify the genes involved in the symbiosis between two
protistan species. Biological screens for symbiosis using mutagenized symbionts
and 2D gel electrophoresis will yield mutants or proteins, respectively, which
can be used ultimately to derive DNA sequence. The sequence data will allow for
the identification of the involved genes.
Charles E. Mitchell Cornell University
Population Biology 0200469
"Effects
of environmental change on a generalist microbial pathogen: barley yellow dwarf
virus in wild grass communities."
A major challenge for
microbial biology is to understand how environmental change affects microbes.
Pathogenic microbes infecting multiple host species are influenced by altered
host community composition. This research is testing how three other components
of environmental change - nitrogen deposition, decreased species diversity, and
land-use change - interact with host community composition to affect barley
yellow dwarf virus, a generalist viral pathogen of grasses.
Karyn Lynn Newman
Univ California-Berkeley Integrated
Plant Biology 0200493
"Investigating
the Role of Cell-to-Cell Communication by the Endophytic Bacterium Xylella
fastidiosa in the Colonization of Grapevines."
Bacterial cells
can communicate using signaling molecules, allowing them to monitor population
size and to coordinate behavior as a group. Xylella fastidiosa colonizes the
xylem vessels of plants, causing blockage and water-stress symptoms in some
hosts. The role of cell-cell signaling and community behavior in successful
colonization of the xylem is being investigated.
Jean J. Pan
University of Minnesota
Population Biology
0200378
"The fungal community on corn (Zea
mays) resistant and susceptible to smut (Ustilago maydis)."
The effects of selective breeding and
changing host genetic environment on non-target, potentially beneficial
microorganisms are often overlooked. This research investigates these effects
by studying the fungal microbial community on corn plants resistant or
susceptible to one its major pathogens, smut. It will have important
implications for understanding how altering the host plant genetic environment
can affect species diversity and genetic structure of non-target
microorganisms.
Jennifer A. Rudgers
Indiana University Population
Biology 0200485
"Do
fungal endosymbionts of grasses structure community diversity and modify food
web dynamics?"
Endophytic fungi
form symbioses with grasses and produce toxic alkaloids that reduce herbivory
to their hosts. This research evaluates how grass endophytes modify the
diversity and dynamics of plant, pathogen, and arthropod assemblages and asks
how fungal alkaloid chemistry influences these effects. This investigation will
expand our understanding of how plant-microbe mutualisms influence community
dynamics and biodiversity.
Chad W. Saltikov
Calif Institute of Technology
Metabolic Biochemistry 0200145
"Molecular
characterization of microbial respiratory arsenate reduction: diversity and
environmental expression of metalloid reductase genes."
Microbial
respiratory arsenate reduction can significantly alter the mobility and
toxicity of arsenic in the environment. Little is known about the molecular
mechanisms for arsenic respiration. The research goals of this research are to
identify genes involved in arsenate respiration in a variety of species,
including Sulfurospirillum and Shewanella strains, and measure arsenate
respiratory activity in contaminated sites.
Emily L. Stowe-Evans
Indiana University Biochemistry
of Gene Expression 0204235
"Microarray
analysis to discover light-quality regulated genes in the cyanobacteria
Fremyella diplosiphon."
Microarrays allow
researchers to analyze global gene expression. Fremyella diplosiphon has an adaptive
response to light color called complementary chromatic adaptatio(CCA). However,
only three operons have been identified as regulated by light color. This
research uses microarrays of PCR amplified genomic fragments to discover novel
genes that are light color regulated and then uses gene-specific microarrays to
examine the expression kinetics of these genes.
Paul D. Straight
Harvard University
Genetics 0200307
"Bacterial-fungal
interactions: novel signals and response mechanisms that influence development
of bacterial communities in the presence of fungi."
In the natural
environment, many microorganisms construct complex communities known as
biofilms. This research focuses on signaling interactions between bacteria and
fungi in the context of biofilms through characterization of multiple
bacterial-fungal pairs. Genetic techniques and microarray analyses are being
used to identify genes involved in dual-species interactions to define
signaling mechanisms important to bacterial-fungal communities.
Alexis S. Templeton
Scripps Inst Oceanography
Metabolic Biochemistry
0200505
"Molecular
and biogeochemical investigations of microbial communities associated with
ocean-ridge basalts."
The proposed
research is directed towards identifying which microorganisms are involved in
the initial stages of basalt weathering reactions, their phylogeny and modes of
metabolic activity, and how transient these microbial communities may be. The
research combines sampling of marine, ocean-ridge environments with laboratory
enrichment culturing techniques and molecular biology methods.
John C. Wertz
Yale University Ecol & Evol Physiology 0200631
"Have colicin type antibiotic genes evolved to increase their
host bacteria
competitiveness, or
are they selfish addictive genes?"
Colicin type
bacteriocins are believed to have evolved as allelopathic agents that confer a
competitive advantage to bacterial strains that harbor them. This research
investigates an alternative hypothesis that colicin plasmids are selfish
elements and utilize a form of post
segregational killing to insure their maintenance by host bacteria.