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Biological Sciences Faculty Publications

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Articles 1201 - 1230 of 1571

Full-Text Articles in Life Sciences

Rapid Evolution Of An Invasive Plant, John L. Maron, Montserrat Vilà, Riccardo Bommarco, Sarah Elmendorf, Paul Beardsley May 2004

Rapid Evolution Of An Invasive Plant, John L. Maron, Montserrat Vilà, Riccardo Bommarco, Sarah Elmendorf, Paul Beardsley

Biological Sciences Faculty Publications

Exotic plants often face different conditions from those experienced where they are native. The general issue of how exotics respond to unfamiliar environments within their new range is not well understood. Phenotypic plasticity has historically been seen as the primary mechanism enabling exotics to colonize large, environmentally diverse areas. However, new work indicates that exotics can evolve quickly, suggesting that contemporary evolution may be more important in invasion ecology than previously appreciated. To determine the influence of contemporary evolution, phenotypic plasticity, and founder effects in affecting phenotypic variation among introduced plants, we compared the size, fecundity, and leaf area of …

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Role Of Hydrophobic Residues In The Central Ectodomain Of Gp41 In Maintaining The Association Between Human Immunodeficiency Virus Type 1 Envelope Glycoprotein Subunits Gp120 And Gp41, Joanne York, Jack H. Nunberg May 2004

Role Of Hydrophobic Residues In The Central Ectodomain Of Gp41 In Maintaining The Association Between Human Immunodeficiency Virus Type 1 Envelope Glycoprotein Subunits Gp120 And Gp41, Joanne York, Jack H. Nunberg

Biological Sciences Faculty Publications

The interaction between the gp120 and gp41 subunits of the human immunodeficiency virus envelope glycoprotein serves to stabilize the virion form of the complex and to transmit receptor-induced conformational changes in gp120 to trigger the membrane fusion activity of gp41. In this study, we used site-directed mutagenesis to identify amino acid residues in the central ectodomain of gp41 that contribute to the stability of the gp120-gp41 association. We identified alanine mutations at six positions, including four tryptophan residues, which result in mutant envelope glycoprotein complexes that fail to retain gp120 on the cell surface. These envelope glycoproteins readily shed their …

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Seasonal Dynamics Of Shallow-Hyporheic-Zone Microbial Community Structure Along A Heavy-Metal Contamination Gradient, Kevin P. Feris, Philip W. Ramsey, Chris Frazar, Matthias Rillig, Johnnie N. Moore, William E. Holben Apr 2004

Seasonal Dynamics Of Shallow-Hyporheic-Zone Microbial Community Structure Along A Heavy-Metal Contamination Gradient, Kevin P. Feris, Philip W. Ramsey, Chris Frazar, Matthias Rillig, Johnnie N. Moore, William E. Holben

Biological Sciences Faculty Publications

Heavy metals contaminate numerous freshwater streams and rivers worldwide. Previous work by this group demonstrated a relationship between the structure of hyporheic microbial communities and the fluvial deposition of heavy metals along a contamination gradient during the fall season. Seasonal variation has been documented in microbial communities in numerous terrestrial and aquatic environments, including the hyporheic zone. The current study was designed to assess whether relationships between hyporheic microbial community structure and heavy-metal contamination vary seasonally by monitoring community structure along a heavy-metal contamination gradient for more than a year. No relationship between total bacterial abundance and heavy metals was …

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Gc Fractionation Enhances Microbial Community Diversity Assessment And Detection Of Minority Populations Of Bacteria By Denaturing Gradient Gel Electrophoresis, William Holben, Keving P. Feris, Anu Kettunen, Juha H. A. Apajalahti Apr 2004

Gc Fractionation Enhances Microbial Community Diversity Assessment And Detection Of Minority Populations Of Bacteria By Denaturing Gradient Gel Electrophoresis, William Holben, Keving P. Feris, Anu Kettunen, Juha H. A. Apajalahti

Biological Sciences Faculty Publications

Effectively and accurately assessing total microbial community diversity is one of the primary challenges in modern microbial ecology. This is particularly true with regard to the detection and characterization of unculturable populations and those present only in low abundance. We report a novel strategy, GC fractionation combined with denaturing gradient gel electrophoresis (GC-DGGE), which combines mechanistically different community analysis approaches to enhance assessment of microbial community diversity and detection of minority populations of microbes. This approach employs GC fractionation as an initial step to reduce the complexity of the community in each fraction. This reduced complexity facilitates subsequent detection of …

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Soil Fungi Alter Interactions Between The Invader Centaurea Maculosa And North American Natives, Ragan M. Callaway, Giles C. Thelen, Sara Barth, Philip W. Ramsey, James E. Gannon Apr 2004

Soil Fungi Alter Interactions Between The Invader Centaurea Maculosa And North American Natives, Ragan M. Callaway, Giles C. Thelen, Sara Barth, Philip W. Ramsey, James E. Gannon

Biological Sciences Faculty Publications

Soil microbes may affect the way exotic invasive plants interact with native neighbors. We investigated the effects of soil fungi on interactions between the invasive weed Centaurea maculosa (spotted knapweed) and six species native to the intermountain prairies of the northwestern United States. We also compared the effect of C. maculosa on the composition of the soil microbial community to that of the native species. In the field, fungicide (Benomyl) reduced AM mycorrhizal colonization of C. maculosa roots by >80%. Fungicide did not significantly reduce non-AM fungi. When grown alone, the biomass of C. maculosa was not affected by the …

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Variation In Sulfide Tolerance Of Photosystem Ii In Phylogenetically Diverse Cyanobacteria From Sulfidic Habitats, Scott R. Miller, Brad M. Bebout Feb 2004

Variation In Sulfide Tolerance Of Photosystem Ii In Phylogenetically Diverse Cyanobacteria From Sulfidic Habitats, Scott R. Miller, Brad M. Bebout

Biological Sciences Faculty Publications

Physiological and molecular phylogenetic approaches were used to investigate variation among 12 cyanobacterial strains in their tolerance of sulfide, an inhibitor of oxygenic photosynthesis. Cyanobacteria from sulfidic habitats were found to be phylogenetically diverse and exhibited an approximately 50-fold variation in photosystem II performance in the presence of sulfide. Whereas the degree of tolerance was positively correlated with sulfide levels in the environment, a strain's phenotype could not be predicted from the tolerance of its closest relatives. These observations suggest that sulfide tolerance is a dynamic trait primarily shaped by environmental variation. Despite differences in absolute tolerance, similarities among strains …

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Splicing Affects Presentation Of Rna Dimerization Signals In Hiv-2 In Vitro, Jean-Marc Lanchy, Quenna N. Szafran, J. Stephen Lodmell Jan 2004

Splicing Affects Presentation Of Rna Dimerization Signals In Hiv-2 In Vitro, Jean-Marc Lanchy, Quenna N. Szafran, J. Stephen Lodmell

Biological Sciences Faculty Publications

During retroviral replication, full-length viral RNAs are encapsidated into new virus particles, while spliced RNAs are excluded. The Retroviridae are unique among viruses in that infectious viral particles contain a dimer of two identical genomic RNA strands. A variety of experimental data has suggested that dimerization and encapsidation of full-length viral RNAs are linked processes, although whether dimerization is a prerequisite for encapsidation, or conversely, dimerization follows encapsidation, has not been firmly established. If dimerization was the sole determinant for encapsidation, then spliced viral RNAs might be expected to display a reduced capacity for dimerization, resulting in their exclusion from …

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Chemical Defenses In Garlic Mustard (Alliaria Petiolata) And Their Potential Role In Species Interactions In Forest Understories, Don Cipollini Jan 2004

Chemical Defenses In Garlic Mustard (Alliaria Petiolata) And Their Potential Role In Species Interactions In Forest Understories, Don Cipollini

Biological Sciences Faculty Publications

Garlic mustard [Alliaria petiolata [(M. Bieb) Cavara & Grande; Brassicaceae] is a European native biennial herb, first recorded on Long Island, NY in the 1860s, and is expanding rapidly in northeastern and midwestern forests in the U.S. and in southern Canada. Garlic mustard flourishes in moist woodlands with moderate exposure to light, but it can grow in a diversity of other habitats. It is found in natural areas, woodlots, and along edges of agricultural fields and lawns throughout North America. Several life history traits likely contribute to the invasiveness of this species. It has a high inbreeding rate and can …

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Comparative Life Histories Of Georgia And Virginia Cotton Rats, Bradley J. Bergstrom, Robert K. Rose Jan 2004

Comparative Life Histories Of Georgia And Virginia Cotton Rats, Bradley J. Bergstrom, Robert K. Rose

Biological Sciences Faculty Publications

Adult hispid cotton rats (Sigmodon hispidus) were collected from the field monthly for >2 years from populations near the northern edge of their range in Virginia and contemporaneously from south-central Georgia. Body measurements and weights were taken at capture, and after dissection embryos, corpora lutea, and placental scars were counted and measured; testes and seminal vesicles were dissected out, measured, and weighed. This allowed comparison of several life-history parameters between the populations and tests of several life-history hypotheses. The breeding season was up to 2 months longer in Georgia than in Virginia, where there was typically a 3-month …

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On The Ecological Status Of The Concept "Boundary Conditions" - A Few Methodological Remarks, Lubomira Burchardt, Krzystof Lastowski, Harold G. Marshall Jan 2004

On The Ecological Status Of The Concept "Boundary Conditions" - A Few Methodological Remarks, Lubomira Burchardt, Krzystof Lastowski, Harold G. Marshall

Biological Sciences Faculty Publications

Plant and animal populations are frequently found in habitats where the environmental conditions are considered extreme or challenging for life form to exist. These conditions may be classified as either: (1) Supreme: a situation characteristic of degradation conditions where only a few species live under stress, and (2) Extra-ordinary: habitats that provide high biodiversity that are under stress conditions. Due to the differences in what we consider extreme conditions, it is necessary to distinguish between these two categories, because they are not comparable. Our presentation will include examples of these two extreme environmental categories.

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Dissecting The Loci Of Low-Level Quinine Resistance In Malaria Parasites, Michael T. Ferdig, Roland A. Cooper, Jianbing Mu, Bingbing Deng, Deirdre A. Joy, Xin-Zhuan Su, Thomas E. Wellems Jan 2004

Dissecting The Loci Of Low-Level Quinine Resistance In Malaria Parasites, Michael T. Ferdig, Roland A. Cooper, Jianbing Mu, Bingbing Deng, Deirdre A. Joy, Xin-Zhuan Su, Thomas E. Wellems

Biological Sciences Faculty Publications

Quinine (QN) remains effective against Plasmodium falciparum, but its decreasing efficacy is documented from different continents. Multiple genes are likely to contribute to the evolution of QN resistance. To locate genes contributing to QN response variation, we have searched a P. falciparum genetic cross for quantitative trait loci (QTL). Results identify additive QTL in segments of chromosomes (Chrs) 13, 7 and 5, and pairwise effects from two additional loci of Chrs 9 and 6 that interact, respectively, with the QTL of Chrs 13 and 7. The mapped segments of Chrs 7 and 5 contain pfcrt, the determinant of …

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Virulence Factors Of The Group A Streptococci And Genes That Regulate Their Expression, Wayne Hines Jan 2004

Virulence Factors Of The Group A Streptococci And Genes That Regulate Their Expression, Wayne Hines

Biological Sciences Faculty Publications

Group A streptococci produce a wide variety of extracellular (cell-associated and released) virulence factors. The function of these factors varies and includes roles in adhesion, spreading, tissue destruction, immune system evasion, and cell toxicity. How these factors are regulated with regard to one another is important for this organism's ability to bring about the variety of diseases this microbe is capable of causing. Therefore, along with the multitude of virulence factors, there are a number of regulatory systems that regulate, either directly or indirectly, the production of these factors and therefore influence the pathogenesis of group A streptococcal infections.

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Phytoplankton Composition Within The Tidal Freshwater-Oligohaline Regions Of The Rappahannock And Pamunkey Rivers In Virginia, Harold G. Marshall, Lubomira Burchardt Jan 2004

Phytoplankton Composition Within The Tidal Freshwater-Oligohaline Regions Of The Rappahannock And Pamunkey Rivers In Virginia, Harold G. Marshall, Lubomira Burchardt

Biological Sciences Faculty Publications

The Rappahannock River is a major river system across north central Virginia prior to entering the Chesapeake Bay. In contrast, the Pamunkey River is smaller in size and joins the Mattoponi River to form the York River, which flows parallel to the Rappahannock before it also flows into Chesapeake Bay. A unique mixing area for both flora and environmental conditions exists in the tidal freshwater-oligohaline region of both rivers. This is a dynamic mixing section where freshwater and estuarine species are subject to the interaction of river flow and daily tidal rhythms. The phytoplankton composition in this region of the …

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A New Pathogenic Virus In The Caribbean Spiny Lobster Panulirus Argus From The Florida Keys, Jeffrey D. Shields, Donald C. Behringer Jr. Jan 2004

A New Pathogenic Virus In The Caribbean Spiny Lobster Panulirus Argus From The Florida Keys, Jeffrey D. Shields, Donald C. Behringer Jr.

Biological Sciences Faculty Publications

A pathogenic virus was diagnosed from juvenile Caribbean spiny lobsters Panulirus argus from the Florida Keys. Moribund lobsters had characteristically milky hemolymph that did not clot. Altered hyalinocytes and semigranulocytes, but not granulocytes, were observed with light microscopy. Infected hemocytes had emarginated, condensed chromatin, hypertrophied nuclei and faint eosinophilic Cowdry-type-A inclusions. In some cases, infected cells were observed in soft connective tissues. With electron microscopy, unenveloped, nonoccluded, icosahedral virions (182 +/- 9 nm SD) were diffusely spread around the inner periphery of the nuclear envelope. Virions also occurred in loose aggregates in the cytoplasm or were free in the hemolymph. …

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Metabolic Rate Models And The Substitutability Of Predator Populations, David R. Chalcraft, William J. Resetarits Jr. Jan 2004

Metabolic Rate Models And The Substitutability Of Predator Populations, David R. Chalcraft, William J. Resetarits Jr.

Biological Sciences Faculty Publications

1. Much of the debate surrounding the consequences of biodiversity loss centres around the issue of whether different species are functionally similar in their effects on ecological processes. In this study, we examined whether populations consisting of smaller, more abundant individuals are functionally similar to populations of the same species with larger, fewer individuals.
2. We manipulated the biomass and density of banded sunfish (Enneacanthus obesus) and measured their impact on populations of Southern leopard frog (Rana sphenocephala) larvae. We also evaluated the ability of models relating metabolic rate to body size to predict the relative …

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Identification And Characterization Of A Nontypeable Haemophilus Influenzae Putative Toxin-Antitoxin Locus, Dayle A. Daines, Justin Jarisch, Arnold L. Smith Jan 2004

Identification And Characterization Of A Nontypeable Haemophilus Influenzae Putative Toxin-Antitoxin Locus, Dayle A. Daines, Justin Jarisch, Arnold L. Smith

Biological Sciences Faculty Publications

Background: Certain strains of an obligate parasite of the human upper respiratory tract, nontypeable Haemophilus influenzae (NTHi), can cause invasive diseases such as septicemia and meningitis, as well as chronic mucosal infections such as otitis media. To do this, the organism must invade and survive within both epithelial and endothelial cells. We have identified a facilitator of NT(Hi) survival inside human cells, virulence-associated protein D (vapDHi, encoded by gene H10450). Both vapDHi and a flanking gene, H10451, exhibit the genetic and physical characteristics of a toxin/antitoxin ( TA) locus, with VapDHi serving as the …

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Ultrastructure Of Mycobacterium Marinum Granuloma In Striped Bass Morone Saxatilis, D. T. Gauthier, W. K. Vogelbein, C. A. Ottinger Jan 2004

Ultrastructure Of Mycobacterium Marinum Granuloma In Striped Bass Morone Saxatilis, D. T. Gauthier, W. K. Vogelbein, C. A. Ottinger

Biological Sciences Faculty Publications

An emerging epizootic of mycobacteriosis currently threatens striped bass Morone saxatilis populations in Chesapeake Bay, USA. Several species of mycobacteria, including Mycobacterium marinum, species resembling M. avium, M. gordonae, M. peregrinum, M. scrofulaceum and M. terrae, and the new species M. shottsii have been isolated from diseased and healthy bass. In this study, we describe the ultrastructure of developing M. marinum granulomas in experimentally infected bass over a period of 45 wk. The primary host response to injected mycobacteria was formation of large macrophage aggregations containing phagocytosed bacilli. M. marinum were always contained within phagosomes. Close …

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Isolation And Characterization Of Mycobacteria From Striped Bass Morone Saxatilis From The Chesapeake Bay, Martha W. Rhodes, Howard Kator, Ilsa Kaattari, David Gauthier, Wolfgang Vogelbein, Christopher A. Ottinger Jan 2004

Isolation And Characterization Of Mycobacteria From Striped Bass Morone Saxatilis From The Chesapeake Bay, Martha W. Rhodes, Howard Kator, Ilsa Kaattari, David Gauthier, Wolfgang Vogelbein, Christopher A. Ottinger

Biological Sciences Faculty Publications

Mycobacteriosis in striped bass Morone saxatilisof Chesapeake Bay, USA, was first diagnosed in 1997 based on the presence of granulomatous inflammation and acid-fast bacteria in skin and spleen. To confirm histopathology, bacteriological detection and identification of mycobacteria were begun using splenic tissue from fish with and without skin ulcerations. On the basis of initial studies using a variety of selective and nonselective media, decontamination, homogenization and incubation conditions, a simple and quantitative recovery method using aseptic necropsy of splenic tissue was developed. Optimal recovery was obtained by spread-plating homogenates on Middlebrook 7H10 agar with incubation for 3 mo at …

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Thermodynamic Characterization Of The Binding Of Activator Of G Protein Signaling 3 (Ags3) And Peptides Derived From Ags3 With G Alpha I1, Anirban Adhikari, Stephen R. Sprang Dec 2003

Thermodynamic Characterization Of The Binding Of Activator Of G Protein Signaling 3 (Ags3) And Peptides Derived From Ags3 With G Alpha I1, Anirban Adhikari, Stephen R. Sprang

Biological Sciences Faculty Publications

Activator of G protein signaling 3 (AGS3) is a guanine nucleotide dissociation inhibitor (GDI) that contains four G protein regulatory (GPR) or GoLoco motifs in its C-terminal domain. The entire C-terminal domain (AGS3-C) as well as certain peptides corresponding to individual GPR motifs of AGS3 bound to G alpha i1 and inhibited the binding of GTP by stabilizing the GDP-bound conformation of G alpha i1. The stoichiometry, free energy, enthalpy, and dissociation constant for binding of AGS3-C to G alpha i1 were determined using isothermal titration calorimetry. AGS3-C possesses two apparent high affinity (Kd approximately 20 nm) and two apparent …

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Mitogenic Effect Of Bartonella Bacilliformis On Human Vascular Endothelial Cells And Involvement Of Groel, Michael F. Minnick, Laura S. Smitherman, D. Scott Samuels Dec 2003

Mitogenic Effect Of Bartonella Bacilliformis On Human Vascular Endothelial Cells And Involvement Of Groel, Michael F. Minnick, Laura S. Smitherman, D. Scott Samuels

Biological Sciences Faculty Publications

Bartonellae are bacterial pathogens for a wide variety of mammals. In humans, bartonellosis can result in angioproliferative lesions that are potentially life threatening to the patient, including bacillary angiomatosis, bacillary peliosis, and verruga peruana. The results of this study show that Bartonella bacilliformis, the agent of Oroya fever and verruga peruana, produces a proteinaceous mitogen for human vascular endothelial cells (HUVECs) that acts in a dose-dependent fashion in vitro with maximal activity at >72 h of exposure and results in a 6- to 20-fold increase in cell numbers relative to controls. The mitogen increases bromodeoxyuridine (BrdU) incorporation into HUVECs …

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Aada Confers Streptomycin Resistance In Borrelia Burgdorferi, Kristi L. Frank, Sharyl F. Bundle, Michele E. Kresge, Christian H. Eggers, D. Scott Samuels Nov 2003

Aada Confers Streptomycin Resistance In Borrelia Burgdorferi, Kristi L. Frank, Sharyl F. Bundle, Michele E. Kresge, Christian H. Eggers, D. Scott Samuels

Biological Sciences Faculty Publications

To enhance genetic manipulation of the Lyme disease spirochete Borrelia burgdorferi, we assayed the aadA gene for the ability to confer resistance to the antibiotics spectinomycin and streptomycin. Using the previously described pBSV2 as a backbone, a shuttle vector, termed pKFSS1, which carries the aadA open reading frame fused to the B. burgdorferi flgB promoter was constructed. The hybrid flgB promoter-aadA cassette confers resistance to spectinomycin and streptomycin in both B. burgdorferi and Escherichia coli. pKFSS1 has a replication origin derived from the 9-kb circular plasmid and can be comaintained in B. burgdorferi with extant shuttle vector pCE320, which has …

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Evolution Of Avian Locomotion: Correlates Of Flight Style, Locomotor Modules, Nesting Biology, Body Size, Development, And The Origin Of Flapping Flight, Kenneth P. Dial Oct 2003

Evolution Of Avian Locomotion: Correlates Of Flight Style, Locomotor Modules, Nesting Biology, Body Size, Development, And The Origin Of Flapping Flight, Kenneth P. Dial

Biological Sciences Faculty Publications

No abstract provided.

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Differences In Hyporheic-Zone Microbial Community Structure Along A Heavy-Metal Contamination Gradient, Kevin P. Feris, Philip W. Ramsey, Frazar Chris, Johnnie N. Moore, James E. Gannon, William E. Holben Sep 2003

Differences In Hyporheic-Zone Microbial Community Structure Along A Heavy-Metal Contamination Gradient, Kevin P. Feris, Philip W. Ramsey, Frazar Chris, Johnnie N. Moore, James E. Gannon, William E. Holben

Biological Sciences Faculty Publications

Heavy metals contaminate numerous freshwater streams and rivers worldwide. Previous work by this group demonstrated a relationship between the structure of hyporheic microbial communities and the fluvial deposition of heavy metals along a contamination gradient during the fall season. Seasonal variation has been documented in microbial communities in numerous terrestrial and aquatic environments, including the hyporheic zone. The current study was designed to assess whether relationships between hyporheic microbial community structure and heavy-metal contamination vary seasonally by monitoring community structure along a heavy-metal contamination gradient for more than a year. No relationship between total bacterial abundance and heavy metals was …

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Selective Plating Underestimates Abundance And Shows Differential Recovery Of Bifidobacterial Species From Human Feces, Juha H. A. Apajalahti, Anu Kettunen, Päivi H. Nurminen, Hanna Jatila, William E. Holben Sep 2003

Selective Plating Underestimates Abundance And Shows Differential Recovery Of Bifidobacterial Species From Human Feces, Juha H. A. Apajalahti, Anu Kettunen, Päivi H. Nurminen, Hanna Jatila, William E. Holben

Biological Sciences Faculty Publications

The aim of the present work was to compare the efficacies and levels of selectivity of different culture-dependent and -independent methods for analyzing bifidobacteria in human stool samples. The three different culture media used here significantly differed from each other, particularly with regard to the recovery of Bifidobacterium adolescentis. Bifidobacterium medium failed to recover B. adolescentis; Beerens medium recovered some B. adolescentis organisms (17% of total bifidobacteria), whereas tomato-Eugon medium recovered mainly B. adolescentis organisms (58% of total bifidobacteria). A culture-independent method that combines GC fractionation of bacterial community DNA and 16S rRNA sequencing indicated that B. adolescentis organisms accounted …

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Monitoring Immediate-Early Gene Expression Through Firefly Luciferase Imaging Of Hrs/J Hairless Mice, Michael E. Geusz, Anne M. Collaco Aug 2003

Monitoring Immediate-Early Gene Expression Through Firefly Luciferase Imaging Of Hrs/J Hairless Mice, Michael E. Geusz, Anne M. Collaco

Biological Sciences Faculty Publications

Background: Gene promoters fused to the firefly luciferase gene (luc) are useful for examining gene regulation in live transgenic mice and they provide unique views of functioning organs. The dynamics of gene expression in cells and tissues expressing luciferase can be observed by imaging this enzyme's bioluminescent oxidation of luciferin. Neural pathways involved in specific behaviors have been identified by localizing expression of immediate-early genes such as c-fos. A transgenic mouse line with luc controlled by the human c-fos promoter (fos::luc) has enabled gene expression imaging in brain slice cultures. To optimize imaging of immediate-early gene expression throughout intact mice, …

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A Structural Linkage Between The Dimerization And Encapsidation Signals In Hiv-2 Leader Rna, J. M. Lanchy, J. D. Ivanovitch, J. Stephen Lodmell Aug 2003

A Structural Linkage Between The Dimerization And Encapsidation Signals In Hiv-2 Leader Rna, J. M. Lanchy, J. D. Ivanovitch, J. Stephen Lodmell

Biological Sciences Faculty Publications

The 5' untranslated leader region of retroviral RNAs contains noncoding information that is essential for viral replication, including signals for transcriptional transactivation, splicing, primer binding for reverse transcription, dimerization of the genomic RNA, and encapsidation of the viral RNA into virions. These RNA motifs have considerable structural and functional overlap. in this study, we investigate the conformational dynamics associated with the use and silencing of a sequence in HIV-2 RNA that is involved in genomic RNA dimerization called stem-loop 1 (SL1) and its relationship with a flanking sequence that is known to be important for encapsidation of viral RNAs. We …

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Ribosomal Localization Of Translation Initiation Factor If2, Stefano Marzi, William Knight, Letizia Brandi, Enrico Caserta, Natalia Soboleva, Walter E. Hill, Claudio O. Gualerzi, J. Stephen Lodmell Aug 2003

Ribosomal Localization Of Translation Initiation Factor If2, Stefano Marzi, William Knight, Letizia Brandi, Enrico Caserta, Natalia Soboleva, Walter E. Hill, Claudio O. Gualerzi, J. Stephen Lodmell

Biological Sciences Faculty Publications

Bacterial translation initiation factor IF2 is a GTP-binding protein that catalyzes binding of initiator fMet-tRNA in the ribosomal P site. The topographical localization of IF2 on the ribosomal subunits, a prerequisite for understanding the mechanism of initiation complex formation, has remained elusive. Here, we present a model for the positioning of IF2 in the 70S initiation complex as determined by cleavage of rRNA by the chemical nucleases Cu(II):1,10-orthophenanthroline and Fe(II):EDTA tethered to cysteine residues introduced into IF2. Two specific amino acids in the GII domain of IF2 are in proximity to helices H3, H4, H17, and H18 of 16S rRNA. …

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River Flows And Water Wars: Emerging Science For Environmental Decision Making, N. Leroy Poff, J. David Allan, Margaret A. Palmer, David D. Hart, Brian D. Richter, Angela H. Arthington, Kevin H. Rogers, Judy L. Meyer, Jack Arthur Stanford Aug 2003

River Flows And Water Wars: Emerging Science For Environmental Decision Making, N. Leroy Poff, J. David Allan, Margaret A. Palmer, David D. Hart, Brian D. Richter, Angela H. Arthington, Kevin H. Rogers, Judy L. Meyer, Jack Arthur Stanford

Biological Sciences Faculty Publications

Real and apparent conflicts between ecosystem and human needs for fresh water are contributing to the emergence of an alternative model for conducting river science around the world. The core of this new paradigm emphasizes the need to forge new partnerships between scientists and other stakeholders where shared ecological goals and river visions are developed, and the need for new experimental approaches to advance scientific understanding at the scales relevant to whole-river management. We identify four key elements required to make this model succeed: existing and planned water projects represent opportunities to conduct ecosystem-scale experiments through controlled river flow manipulations; …

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Effect Of Phosphorus Amendments On Present Day Plankton Communities In Pelagic Lake Erie, Steven W. Wilhelm, Jennifer M. Debruyn, Osnat Gillor, Michael R. Twiss, Kasey Livingston, Richard A. Bourbonniere, Lisa D. Pickell, Charles G. Trick, Amanda L. Dean, Robert Michael Mckay Jul 2003

Effect Of Phosphorus Amendments On Present Day Plankton Communities In Pelagic Lake Erie, Steven W. Wilhelm, Jennifer M. Debruyn, Osnat Gillor, Michael R. Twiss, Kasey Livingston, Richard A. Bourbonniere, Lisa D. Pickell, Charles G. Trick, Amanda L. Dean, Robert Michael Mckay

Biological Sciences Faculty Publications

To address questions regarding the potential impact of elevated total phosphorus (TP) inputs (due to relaxed regulations of TP loading), a series of TP enrichment experiments were conducted at pelagic stations in the 3 hydrologically distinct basins of Lake Erie. Results of nutrient assimilation measurements and assays for nutrient bioavailability suggest that the chemical speciation, and not concentration, of nitrogenous compounds may influence phytoplankton community structure; this in turn may lead to the selective proliferation of cyanobacteria in the eastern basin of the lake. Assays with cyanobacterial bioluminescent reporter systems for P and N availability as well as N-tot:P-tot assimilation …

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Differences In Cottonwood Growth Between A Losing And A Gaining Reach Of An Alluvial Floodplain, Mary J. Harner, Jack Arthur Stanford Jun 2003

Differences In Cottonwood Growth Between A Losing And A Gaining Reach Of An Alluvial Floodplain, Mary J. Harner, Jack Arthur Stanford

Biological Sciences Faculty Publications

Interstitial flow of river (hyporheic) water influences algal productivity, benthic assemblages, and locations of fish spawning. However, little is known of the effects of hyporheic flow on the growth of riparian vegetation. By increasing water availability and nutrient delivery, regional upwelling of hyporheic water may increase the growth of terrestrial vegetation. We tested and accepted the hypothesis that cottonwood trees (Populus trichocarpa) in a gaining reach of an alluvial floodplain grow faster than trees in a losing reach by comparing basal areas and ages on an expansive floodplain in western Montana (USA). Trees in the gaining reach had …

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