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Biological Sciences Faculty Publications

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Articles 1381 - 1410 of 1571

Full-Text Articles in Life Sciences

Crystal Structure Of The Adenylyl Cyclase Activator G(Sα), Roger K. Sunahara, John J.G. Tesmer, Alfred G. Gilman, Stephen R. Sprang Dec 1997

Crystal Structure Of The Adenylyl Cyclase Activator G(Sα), Roger K. Sunahara, John J.G. Tesmer, Alfred G. Gilman, Stephen R. Sprang

Biological Sciences Faculty Publications

The crystal structure of G(sα), the heterotrimeric G protein α subunit that stimulates adenylyl cyclase, was determined at 2.5 Å in a complex with guanosine 5'-O-(3-thio-triphosphate) (GTPγS). G(sα) is the prototypic member of a of GTP-binding proteins that regulate the activities of effectors in a hormone-dependent manner. Comparison of the structure of G(sα)·GTPγS with that of G(iα)·GTPγS suggest that their effector specificity is primarily dictated by the shape of the binding surface formed by the switch II helix and the α3-β5 loop, despite the high sequence homology of these elements. In contrast, sequence divergence explains the inability of regulators of …

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Crystal Structure Of The Catalytic Domains Of Adenylyl Cyclase In A Complex With G(Sα)·Gtpγς, John J.G. Tesmer, Roger K. Sunahara, Alfred G. Gilman, Stephen R. Sprang Dec 1997

Crystal Structure Of The Catalytic Domains Of Adenylyl Cyclase In A Complex With G(Sα)·Gtpγς, John J.G. Tesmer, Roger K. Sunahara, Alfred G. Gilman, Stephen R. Sprang

Biological Sciences Faculty Publications

The crystal structure of a soluble, catalytically active form of adenylyl cyclase in a complex with its stimulatory heterotrimeric G protein α subunit (G(sα)) and forskolin was determined to a resolution of 2.3 angstroms. When P-site inhibitors were soaked into native crystals of the complex, the active site of adenylyl cyclase was located and structural elements important for substrate recognition and catalysis were identified. On the basis of these and other structures, a molecular mechanism is proposed for the activation of adenylyl cyclase by G(sα).

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Ecophysiological Responses Of Three Riparian Graminoids To Changes In The Soil Water Table, Anna Sala, Robert S. Nowak Nov 1997

Ecophysiological Responses Of Three Riparian Graminoids To Changes In The Soil Water Table, Anna Sala, Robert S. Nowak

Biological Sciences Faculty Publications

We examined the effect of changes in soil water table on the water relations, leaf gas exchange, and aboveground biomass of three riparian graminoids native to the semiarid western United States: Carex lanuginosa, Juncus balticus, and Carex nebrascensis. All three species co-occur at the wettest microhabitats within riparian corridors, but J. balticus and C. nebrascensis extend into drier areas. Lowering the water table to 1 m had little effect on the leaf gas exchange characteristics of the three graminoids. In the greenhouse, experimental reductions of the water table when plants had three fully mature leaves did not affect gas exchange …

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Competition And Facilitation: A Synthetic Approach To Interactions In Plant Communities, Ragan M. Callaway, Lawrence R. Walker Oct 1997

Competition And Facilitation: A Synthetic Approach To Interactions In Plant Communities, Ragan M. Callaway, Lawrence R. Walker

Biological Sciences Faculty Publications

Interactions among organisms take place within a complex milieu of abiotic and biotic processes, but we generally study them as solitary phenomena. Complex combinations of negative and positive interactions have been identified in a number of plant communities. The importance of these two processes in structuring plant communities can best be understood by comparing them along gradients of abiotic stress, consumer pressure, and among different life stages, sizes, and densities of the interacting species. Here, we discuss the roles of life stage, physiology, indirect interactions, and the physical environment on the balance of competition and facilitation in plant communities.

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Characterization Of The Sediment Bacterial Community In Groundwater Discharge Zones Of An Alkaline Fen: A Seasonal Study, Timothy C. Gsell, William E. Holben, Roy M. Ventullo Aug 1997

Characterization Of The Sediment Bacterial Community In Groundwater Discharge Zones Of An Alkaline Fen: A Seasonal Study, Timothy C. Gsell, William E. Holben, Roy M. Ventullo

Biological Sciences Faculty Publications

The cell density, activity, and community structure of the bacterial community in wetland sediments were monitored over a 13-month period. The study was performed at Cedar Bog, an alkaline fen. The objective was to characterize the relationship between the sediment bacterial community in groundwater upwelling zones and the physical and chemical factors which might influence the community structure and activity. DNA, protein, and lipid synthesis were measured at three different upwelling zones by using [H-3]thymidine, [C-14]leucine, and [C-14]glucose incorporation, respectively. The physiological status (apparent stress) of the consortium was assessed by comparing [C-14]glucose incorporation into membrane and that into storage …

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Structure Of Rgs4 Bound To Alf4--Activated G(Iα1): Stabilization Of The Transition State For Gtp Hydrolysis, John J.G. Tesmer, David M. Berman, Alfred G. Gilman, Stephen R. Sprang Apr 1997

Structure Of Rgs4 Bound To Alf4--Activated G(Iα1): Stabilization Of The Transition State For Gtp Hydrolysis, John J.G. Tesmer, David M. Berman, Alfred G. Gilman, Stephen R. Sprang

Biological Sciences Faculty Publications

RGS proteins are GTPase activators for heterotrimeric G proteins. We report here the 2.8 Å resolution crystal structure of the RGS protein RGS4 complexed with G(iα1)-Mg2+-GDP-AlF4. Only the core domain of RGS4 is visible in the crystal. The core domain binds to the three switch regions of G(iα1), but does not contribute catalytic residues that directly interact with either GDP or AlF4. Therefore, RGS4 appears to catalyze rapid hydrolysis of GTP primarily by stabilizing the switch regions of G(iα1), although the conserved Asn-128 from RGS4 could also play a catalytic role by interacting with …

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A Carboxy-Terminal Processing Protease Gene Is Located Immediately Upstream Of The Invasion-Associated Locus From Bartonella Bacilliformis, Samuel J. Mitchell, Michael F. Minnick Apr 1997

A Carboxy-Terminal Processing Protease Gene Is Located Immediately Upstream Of The Invasion-Associated Locus From Bartonella Bacilliformis, Samuel J. Mitchell, Michael F. Minnick

Biological Sciences Faculty Publications

A gene with homology to those encoding an unusual class of C-terminal processing proteases that flanks the invasion-associated locus ialAB of Bartonella bacilliformis has been identified. The 1302 bp gene, termed ctpA, is located immediately upstream of the ialA gene and encodes a predicted nascent product of 434 amino acids, producing a mature protein of 411 amino acid residues. The Bartonella CtpA appears to undergo autolysis in vitro, producing multiple products of 43-46 kDa, and a second group of products of 36-37 kDa. Production of CtpA in vivo gives a single product of 41.8 kDa. In addition to a computer-predicted …

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Reversion Rates In A Leub Auxotroph Of Escherichia Coli K-12 Correlate With Ppgpp Levels During Exponential Growth, Barbara E. Wright, Michael F. Minnick Mar 1997

Reversion Rates In A Leub Auxotroph Of Escherichia Coli K-12 Correlate With Ppgpp Levels During Exponential Growth, Barbara E. Wright, Michael F. Minnick

Biological Sciences Faculty Publications

Two isogenic strains of Escherichia coli K-12 differing only in relA, as well as two spoT transductants of the relA- strain, were examined with respect to ppGpp levels and reversion rates of a leuB- allele under nine different conditions. A positive correlation was established between reversion rates and the steady-state concentration of ppGpp during exponential growth. The leuB genes from two leuB- strains (isogenic except for relA) were cloned and sequenced and found to contain a single mutation, namely, a C-to-T transition at nucleotide 857. This mutation resulted in a serine-to-leucine substitution at amino acid residue 286 of the LeuB …

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Do Biochemical Exaptations Link Evolution Of Defense And Pollination Systems? Historical Hypotheses And Experimental Tests With Dalechampia Vines, Jerome J. Howard Mar 1997

Do Biochemical Exaptations Link Evolution Of Defense And Pollination Systems? Historical Hypotheses And Experimental Tests With Dalechampia Vines, Jerome J. Howard

Biological Sciences Faculty Publications

Mapping resin secretion and pollination ecology onto the estimated phylogeny of species of the euphorb vine Dalechampia generated two historical hypotheses: resin rewards offered to pollinators by Dalechampia flowers evolved by minor modification of a preexisting, resin-based, floral defense system, and resin defense of leaves in advanced species evolved by modification of the preexisting resin-reward system. From these hypotheses, we derived two predictions: floral reward resins are chemically similar to putative floral defense resins and exhibit antiherbivore activities, and foliar resins are chemically similar to reward resins and also exhibit antiherbivore activities. We tested these predictions by chemical analyses and …

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G Protein Mechanisms: Insights From Structural Analysis, Stephen R. Sprang Jan 1997

G Protein Mechanisms: Insights From Structural Analysis, Stephen R. Sprang

Biological Sciences Faculty Publications

This review is concerned with the structures and mechanisms of a superfamily of regulatory GTP hydrolases (G proteins). G proteins include Ras and its close homologs, translation elongation factors, and heterotrimeric G proteins. These proteins share a common structural core, exemplified by that of p21(ras) (Ras), and significant sequence identity, suggesting a common evolutionary origin. Three-dimensional structures of members of the G protein superfamily are considered in light of other biochemical findings about the function of these proteins. Relationships among G protein structures are discussed, and factors contributing to their low intrinsic rate of GTP hydrolysis are considered. Comparison of …

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Conservation Implications Of A Multi-Scale Study Of Flammulated Owl (Otus Flammeolus) Habitat Use In The Northern Rocky Mountains, Usa, Vita Wright, Sallie J. Hejl, Richard L. Hutto Jan 1997

Conservation Implications Of A Multi-Scale Study Of Flammulated Owl (Otus Flammeolus) Habitat Use In The Northern Rocky Mountains, Usa, Vita Wright, Sallie J. Hejl, Richard L. Hutto

Biological Sciences Faculty Publications

Our multi-scale analysis of Flammulated Owl (Otus flammeolus) habitat use in the northern Rocky Mountains indicates some landscapes may be unsuitable for this species. As a result, there may be less habitat available for Flammulated Owls than thought based on the results of microhabitat studies. Thus, we suggest Flammulated Owl habitat conservation measures be based on the results of landscape-level, as well as microhabitat studies. Habitat conservation and restoration efforts in the ponderosa pine ecosystem should retain large trees, large snags, understory tree thickets, and grassland openings within landscapes that contain an abundance of suitable forest types.

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Recovery Of Crenarchaeotal Ribosomal Dna Sequences From Freshwater-Lake Sediments, Christa Schleper, William E. Holben, Hans-Peter Klenk Jan 1997

Recovery Of Crenarchaeotal Ribosomal Dna Sequences From Freshwater-Lake Sediments, Christa Schleper, William E. Holben, Hans-Peter Klenk

Biological Sciences Faculty Publications

We report several novel environmental sequences of archaea from the kingdom Crenarchaeota, recovered from anaerobic freshwater-lake sediments in Michigan. A nested PCR approach with Archaea- and Crenarchaeota-specific primers was used to amplify partial Small-subunit ribosomal DNAs. Phylogenetic analysis of seven sequences shows that these DNAs represent a monophyletic lineage diverging prior to all recently identified crenarchaeotal phylotypes isolated from temperate environments. Including our lineage, all uncultured crenarchaeotal sequences recovered from moderate or told environments form a distinct, monophyletic group separate from the ''genuine'' thermophilic crenarchaeota. Our finding extends the emerging picture that crenarchaeota, thought until recently to be solely extreme …

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Factors Affecting The Recruitment Of Juvenile Caribbean Spiny Lobsters Dwelling In Macroalgae, Mark J. Butler Iv, William F. Herrnkind, John H. Hunt Jan 1997

Factors Affecting The Recruitment Of Juvenile Caribbean Spiny Lobsters Dwelling In Macroalgae, Mark J. Butler Iv, William F. Herrnkind, John H. Hunt

Biological Sciences Faculty Publications

In south Florida, Caribbean spiny lobsters (Panulirus argus) settle and spend their first few months in macroalgae or seagrass. After a few months, these ''algal-phase'' juveniles emerge from vegetation and, as ''postalgal-phase'' juveniles, seek refuge in crevices, often dwelling in groups. The importance of crevice shelters in determining the abundance of postalgal-phase juvenile spiny lobsters has been studied but we know little about the processes affecting lobster distribution and survival during their cryptic algal-dwelling phase. We found that postlarval supply varied independently of changes in the structure of macroalgal settlement habitat. For this reason, postlarval supply alone can not reliably …

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Problems With The Interpretation Of Mark-Release-Recapture Data In Subterranean Termites (Isoptera: Rhinotermitidae), Anthony D. Curtis, Deborah A. Waller Jan 1997

Problems With The Interpretation Of Mark-Release-Recapture Data In Subterranean Termites (Isoptera: Rhinotermitidae), Anthony D. Curtis, Deborah A. Waller

Biological Sciences Faculty Publications

The Lincoln index (Peterson method) is frequently used to estimate animal population size in mark-release-recapture studies. We tested the accuracy of this method to estimate termite colony size using logs infested with termites that were maintained in the laboratory. Termites were fed paper towels dyed either with 0.05% or 0.1% (w/w) of the dye marker Nile blue and released into their host logs in the laboratory. Following recapture a week later, estimates of termite population size for termites dyed with 0.05% Nile blue, and were approximately 3 times greater for termites dyed with 0.1% Nile blue. Concentrations of 0.1% Nile …

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Seasonal Abundance Of Autotrophic Picoplankton In The Pagan River, A Nutrient Enriched Subestuary Of The James River, Virginia, Lillian N. Davis, Karen A. Phillips, Harold G. Marshall Jan 1997

Seasonal Abundance Of Autotrophic Picoplankton In The Pagan River, A Nutrient Enriched Subestuary Of The James River, Virginia, Lillian N. Davis, Karen A. Phillips, Harold G. Marshall

Biological Sciences Faculty Publications

Autotrophic picoplankton had average monthly concentrations of 73.5 X 106 cells/L in the Pagan River, with summer-early fall maxima of 108 cells/L. The abundance peaks increased with rising water temperatures, declining to their least abundance in mid-winter (105 cells/L).

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A Quantitative Study Of Diet In Three Species Of Rodents In Natural And Irrigated Savanna Fields, Safianu Rabiu, Robert K. Rose Jan 1997

A Quantitative Study Of Diet In Three Species Of Rodents In Natural And Irrigated Savanna Fields, Safianu Rabiu, Robert K. Rose

Biological Sciences Faculty Publications

During July, 1990 - June, 1992 we collected stomach contents of necropsied rodents that totalled 494 Arvicanthis niloticus (Desmarest, 1822), 356 Mastomys natalensis (Smith, 1834) and 273 Tatera valida (Wroughton, 1906) from natural, savanna fields in Nigeria, and 528 Arvicanthis and 367 Mastomys from nearby irrigated fields, where Tatera was never trapped. The materials were processed and microscopically analyzed to determine patterns of diet selection. Sites were sampled for vegetative cover and rodent food resources. More than 90% of the stomach materials could be identified to one of four categories: dicots (vegetative), monocots (vegetative), seeds, and insects. Seeds constituted approximately …

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The Drosophila Melanogaster Rad54 Homolog, Dmrad54, Is Involved In The Repair Of Radiation Damage And Recombination, Rolf Kooistra, José B. M. Zonneveld, Anja De Jong, Jan C. J. Eeken, Chris J. Osgood, Jean-Marie Buerstedde, Paul H. M. Lohman, Albert Pastink Jan 1997

The Drosophila Melanogaster Rad54 Homolog, Dmrad54, Is Involved In The Repair Of Radiation Damage And Recombination, Rolf Kooistra, José B. M. Zonneveld, Anja De Jong, Jan C. J. Eeken, Chris J. Osgood, Jean-Marie Buerstedde, Paul H. M. Lohman, Albert Pastink

Biological Sciences Faculty Publications

The RAD54 gene of Saccharomyces cerevisiae plays a crucial role in recombinational repair of double-strand breaks in DNA. Here the isolation and functional characterization of the RAD54 homolog of the fruit fly Drosophila melanogaster, DmRAD54, are described. The putative Dmrad54 protein displays 46 to 57% identity to its homologs from yeast and mammals. DmRAD54 RNA was detected at all stages of fly development, but an increased level was observed in early embryos and ovarian tissue. To determine the function of DmRAD54, a null mutant was isolated by random mutagenesis. DmRAD54-deficient flies develop normally, but the females …

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Small-Scale Settlement Patterns Of The Oyster Crassostrea Virginica On A Constructed Intertidal Reef, Ian K. Bartol, Roger Mann Jan 1997

Small-Scale Settlement Patterns Of The Oyster Crassostrea Virginica On A Constructed Intertidal Reef, Ian K. Bartol, Roger Mann

Biological Sciences Faculty Publications

The construction of three-dimensional, intertidal reefs resembling those widely present during colonial times in the Chesapeake Bay, but now absent due to years of overharvesting, may provide a more ecologically advantageous environment for oyster settlement and subsequent survival than present subtidal, two-dimensional habitats. We examined settlement processes on a constructed, 210 x 30 m intertidal reef composed of oyster shell. The reef was destructively and non-destructively sampled weekly throughout the summer and fall at tidal heights ranging from 30 cm above to 90 cm below mean low water (MLW) and at two substrate levels (reef surface and 10 cm below …

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Pseudoreplication Revisited, Robert A. Heffner, Mark J. Butler Iv, Colleen Keelan Reilly Dec 1996

Pseudoreplication Revisited, Robert A. Heffner, Mark J. Butler Iv, Colleen Keelan Reilly

Biological Sciences Faculty Publications

No abstract provided.

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Structures Of The Extracellular Domain Of The Type I Tumor Necrosis Factor Receptor, James H. Naismith, Tracey Q. Devine, Tadahiko Kohno, Stephen R. Sprang Nov 1996

Structures Of The Extracellular Domain Of The Type I Tumor Necrosis Factor Receptor, James H. Naismith, Tracey Q. Devine, Tadahiko Kohno, Stephen R. Sprang

Biological Sciences Faculty Publications

Background: Tumor necrosis factor (TNF) is a powerful cytokine that is involved in immune and pro-inflammatory responses. Two TNF receptors that belong to the cysteine-rich low affinity nerve growth factor receptor family (TNF-R1 and TNF-R2) are the sole mediators of TNF signalling. Signalling is thought to occur when a trimer of TNF binds to the extracellular domains of two or three receptor molecules, which permits aggregation and activation of the cytoplasmic domains. The complex is then internalized within an endocytic vesicle, whereupon it dissociates at low pH. Structure of the soluble extracellular domain of the receptor (sTNF-R1) both in the …

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Structure Of The Gdp-Pi Complex Of Gly203→Ala G(Iα1): A Mimic Of The Ternary Product Complex Of Galpha-Catalyzed Gtp Hydrolysis, Albert M. Berghuis, Ethan Lee, André S. Raw, Alfred G. Gilman, Stephen R. Sprang Nov 1996

Structure Of The Gdp-Pi Complex Of Gly203→Ala G(Iα1): A Mimic Of The Ternary Product Complex Of Galpha-Catalyzed Gtp Hydrolysis, Albert M. Berghuis, Ethan Lee, André S. Raw, Alfred G. Gilman, Stephen R. Sprang

Biological Sciences Faculty Publications

Background: G proteins play a vital role in transmembrane signalling events. In their inactive form G proteins exist as heterotrimers consisting of an α subunit, complexed with GDP and a dimer of βγ subunits. Upon stimulation by receptors, G protein α subunits exchange GDP for GTP and dissociate from βγ. Thus activated, α subunits stimulate or inhibit downstream effectors. The duration of the activated state corresponds to the single turnover rate of GTP hydrolysis, which is typically in the range of seconds. In G(iα1), the Gly203→Ala mutation reduces the affinity of the substrate for Mg2+, inhibits a key …

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Directed Insertion Of A Selectable Marker Into A Circular Plasmid Of Borrelia Burgdorferi, Patricia Rosa, D. Scott Samuels, Daniel Hogan, Brian Stevenson, Sherwood Casjens, Kit Tilly Oct 1996

Directed Insertion Of A Selectable Marker Into A Circular Plasmid Of Borrelia Burgdorferi, Patricia Rosa, D. Scott Samuels, Daniel Hogan, Brian Stevenson, Sherwood Casjens, Kit Tilly

Biological Sciences Faculty Publications

Studies of the biology of Borrelia burgdorferi and the pathogenesis of Lyme disease are severely limited by the current lack of genetic tools. As an initial step toward facile genetic manipulation of this pathogenic spirochete, we have investigated gene inactivation by allelic exchange using a mutated borrelial gyrB gene that confers resistance to the antibiotic coumermycin A(1) as a selectable marker. We have transformed B. burgdorferi by electroporation with a linear fragment of DNA in which this selectable marker was flanked by sequences from a native borrelial 26-kb circular plasmid. We have identified coumermycin A(1)-resistant transformants in which gyrB had …

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Competition And Facilitation: Contrasting Effects Of Artemisia Tridentata On Desert Vs Montane Pines, Ragan M. Callaway, Eh Delucia, Darrin Moore, R Nowak, W. H. Schlesinger, Brenda J. Moor Oct 1996

Competition And Facilitation: Contrasting Effects Of Artemisia Tridentata On Desert Vs Montane Pines, Ragan M. Callaway, Eh Delucia, Darrin Moore, R Nowak, W. H. Schlesinger, Brenda J. Moor

Biological Sciences Faculty Publications

Circumstantial evidence suggests that Artemisia tridentata may out-compete Pinus ponderosa and P. jefferyi for water at ecotones between shrub steppe and montane forest vegetation in the Great Basin. Other studies indicate that within the shrub steppe Artemisia may act as a nurse plant for a third species of pine, P. monophylla. We used field experiments to study these contrasting effects of Artemisia on P, ponderosa and P. monophylla within the contest of the distributional patterns in western Nevada of all three species on andesite, and on sites where hydrothermal activity has altered the andesite. At intermediate elevations in the Great …

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A Protocol For Ecosystem Management, Jack A. Stanford, G. C. Poole Aug 1996

A Protocol For Ecosystem Management, Jack A. Stanford, G. C. Poole

Biological Sciences Faculty Publications

No abstract provided.

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Abiotic Stress And The Relative Importance Of Interference And Facilitation In Montane Bunchgrass Communities In Western Montana, John T. Greenlee, Ragan M. Callaway Aug 1996

Abiotic Stress And The Relative Importance Of Interference And Facilitation In Montane Bunchgrass Communities In Western Montana, John T. Greenlee, Ragan M. Callaway

Biological Sciences Faculty Publications

No abstract provided.

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Evidence For Acquisition In Nature Of A Chromosomal 2,4-Dichlorophenoxyacetic Acid/(Alpha)-Ketoglutarate Dioxygenase Gene By Different Burkholderia Spp., V. Grace Matheson, Larry J. Forney, Yuichi Suwa, Cindy H. Nakahatsu, Alan J. Sexstone, William E. Holben Jul 1996

Evidence For Acquisition In Nature Of A Chromosomal 2,4-Dichlorophenoxyacetic Acid/(Alpha)-Ketoglutarate Dioxygenase Gene By Different Burkholderia Spp., V. Grace Matheson, Larry J. Forney, Yuichi Suwa, Cindy H. Nakahatsu, Alan J. Sexstone, William E. Holben

Biological Sciences Faculty Publications

We characterized the gene required to initiate the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by the soil bacterium Burkholderia sp. strain TFD6, which hybridized to the tfdA gene of the canonical 2,4-D catabolic plasmid pJP4 under low-stringency conditions. Cleavage of the ether bond of 2,4-D by cell extracts of TFD6 proceeded by an (alpha)-ketoglutarate-dependent reaction,characteristic of TfdA (F. Fukumori and R. P. Hausinger, J. Bacteriol. 175:2083-2086, 1993). The TFD6 tfdA gene was identified in a recombinant plasmid which complemented a tfdA transposon mutant of TFD6 created by chromosomal insertion of Tn5. The plasmid also expressed TfdA activity in Escherichia coli …

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Characterization Of A Chromosomally Encoded 2,4-Dichlorophenoxyacetic Acid/A-Ketoglutarate Dioxygenase From Burkholderia Sp. Strain Rasc, Yuichi Suwa, Alice D. Wright, Fumitasu Fukimori, Kathy A. Nummy, Robert P. Hausinger, William E. Holben, Larry J. Forney Jul 1996

Characterization Of A Chromosomally Encoded 2,4-Dichlorophenoxyacetic Acid/A-Ketoglutarate Dioxygenase From Burkholderia Sp. Strain Rasc, Yuichi Suwa, Alice D. Wright, Fumitasu Fukimori, Kathy A. Nummy, Robert P. Hausinger, William E. Holben, Larry J. Forney

Biological Sciences Faculty Publications

The findings of previous studies indicate that the genes required for metabolism of the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) are typically encoded on broad-host-range plasmids. However, characterization of plasmid-cured strains of Burkholderia sp. strain RASC, as well as mutants obtained by transposon mutagenesis, suggested that the 2,4-D catabolic genes were located on the chromosome of this strain. Mutants of Burkholderia strain RASC unable to degrade 2,4-D (2,4-D- strains) were obtained by insertional inactivation with Tn5. One such mutant (d1) was shown to have Tn5 inserted in tfdARASC, which encodes 2,4-D/alpha-ketoglutarate dioxygenase. This is the first reported example of a …

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Impact Of A Parasitic Plant On The Structure And Dynamics Of Salt Marsh Vegetation, Steven C. Pennings, Ragan M. Callaway Jul 1996

Impact Of A Parasitic Plant On The Structure And Dynamics Of Salt Marsh Vegetation, Steven C. Pennings, Ragan M. Callaway

Biological Sciences Faculty Publications

We investigated the effect of a native parasitic plant, Cuscuta salina, on the structure and dynamics of the plant community in a California salt marsh. Cuscuta was common in the middle marsh zones. The abundance of Cuscuta was positively correlated with the abundance of Limonium californicum at two sampling scales (0.25— and ≈\approx40—m2 quadrats). Sampling at the scale of individual plants indicated that the dominant plant in the marsh, Salicornia virginica, was preferred by Cuscuta as a host over Arthrocnemum subterminale, Limonium californicum, and Frankenia salina. This result was confirmed with host—choice experiments in the field. Based on spatial …

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Temperature-Driven Variation In Substrate Oxygenation And The Balance Of Competition And Facilitation, Ragan M. Callaway, Leah King Jun 1996

Temperature-Driven Variation In Substrate Oxygenation And The Balance Of Competition And Facilitation, Ragan M. Callaway, Leah King

Biological Sciences Faculty Publications

Emergent wetland plants often alleviate the effects of anaerobic soils on root respiration by passively transporting oxygen belowground through continuous air spaces (aerenchyma) in leaves and roots. Oxygen leaked from the roots into the rhizosphere may oxidize minerals in the soil or become available to other plants. Some spatial patterns in marsh plant communities suggest interspecific facilitative interactions, but there is little experimental evidence for interplant facilitation via soil oxygenation. We investigated the capability of the widespread, highly aerenchymous wetland plant, Typa latifolia, to aerate sediments and affect the growth of two non—aerenchymous neighbors, Salix exigua and Myosotis laxa, both …

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Analysis Of Linear Plasmid Dimers In Borrelia Burgdorferi Sensu Lato Isolates: Implications Concerning The Potential Mechanism Of Linear Plasmid Replication, Richard T. Marconi, Sherwood Casjens, Ulrike G. Munderloh, D. Scott Samuels Jun 1996

Analysis Of Linear Plasmid Dimers In Borrelia Burgdorferi Sensu Lato Isolates: Implications Concerning The Potential Mechanism Of Linear Plasmid Replication, Richard T. Marconi, Sherwood Casjens, Ulrike G. Munderloh, D. Scott Samuels

Biological Sciences Faculty Publications

The Borrelia genome is composed of a linear chromosome and a number of variable circular and linear plasmids. Atypically large linear plasmids of 92 to 105 kb have been identified in several Borrelia burgdorferi sensu lato isolates and characterized. These plasmids carry the p27 and ospAB genes, which in other isolates reside on a 50-kb plasmid. Here we demonstrate that these plasmids are dimers of the 50-kb ospAB plasmid (pAB50). The 94-kb plasmid from isolate VS116, pVS94, was an exception and did not hybridize with any plasmid gene probes. When this plasmid was used as a probe, homologous sequences in …

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