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Full-Text Articles in Life Sciences
Antigen Polymorphism In Borrelia Hermsii, A Clonal Pathogenic Bacterium, Stephen M. Rich, Stanley A. Sawyer, Alan G. Barbour
Antigen Polymorphism In Borrelia Hermsii, A Clonal Pathogenic Bacterium, Stephen M. Rich, Stanley A. Sawyer, Alan G. Barbour
Stephen M. Rich
The relapsing fever spirochete, Borrelia hermsii, escapes immune selection by alternating expression of surface lipoprotein alleles. The switch results from a duplicative transposition of one of several surface lipoprotein-encoding nucleotide sequences into the singular expression site. These nucleotide sequences constitute a large gene family whose diversity originated, in some cases, before the major divergences of Borrelia species. We have examined the B. hermsii vsp subfamily of alleles, which are carried on linear plasmids within each cell and maintained in several diverse copies as an antigenic archive. Each encodes a distinct serotype-specific protein. We sequenced more than 90% of the alleles …
Protective Killed Leptospira Borgpetersenii Vaccine Induces Potent Th1 Immunity Comprising Responses By Cd4 And Gammadelta T Lymphocytes, B. M. Naiman, D. Alt, C. A. Bolin, R. Zuerner, Cynthia Baldwin
Protective Killed Leptospira Borgpetersenii Vaccine Induces Potent Th1 Immunity Comprising Responses By Cd4 And Gammadelta T Lymphocytes, B. M. Naiman, D. Alt, C. A. Bolin, R. Zuerner, Cynthia Baldwin
Cynthia Baldwin
Leptospira borgpetersenii serovar hardjo is the most common cause of bovine leptospirosis and also causes zoonotic infections of humans. A protective killed vaccine against serovar hardjo was shown to induce strong antigen-specific proliferative responses by peripheral blood mononuclear cells (PBMC) from vaccinated cattle by 2 months after the first dose of vaccine. This response was absent from nonvaccinated control cattle. The mean response peaked by 2 months after completion of the two-dose vaccination regimen, and substantial proliferation was measured in in vitro cultures throughout the 7 months of the study period. Variations in magnitude of the response occurred among the …
Reductive Presipitation Of Gold By Dissimilatory Fe(Iii)-Reducing Bacteria And Archaea, Kazem Kashefi, Jason M. Tor, Kelly P. Nevin, Derek Lovley
Reductive Presipitation Of Gold By Dissimilatory Fe(Iii)-Reducing Bacteria And Archaea, Kazem Kashefi, Jason M. Tor, Kelly P. Nevin, Derek Lovley
Kelly Nevin
Studies with a diversity of hyperthermophilic and mesophilic dissimilatory Fe(III)-reducing Bacteria andArchaea demonstrated that some of these organisms are capable of precipitating gold by reducing Au(III) to Au(0) with hydrogen as the electron donor. These studies suggest that models for the formation of gold deposits in both hydrothermal and cooler environments should consider the possibility that dissimilatory metal-reducing microorganisms can reductively precipitate gold from solution.
Isolation And Characterization Of A Soluble Nadph-Dependant Fe(Iii) Reductase From Geobacter Sulfurreducens, Franz Kaufmann, Derek Lovley
Isolation And Characterization Of A Soluble Nadph-Dependant Fe(Iii) Reductase From Geobacter Sulfurreducens, Franz Kaufmann, Derek Lovley
Derek Lovley
NADPH is an intermediate in the oxidation of organic compounds coupled to Fe(III) reduction in Geobacter species, but Fe(III) reduction with NADPH as the electron donor has not been studied in these organisms. Crude extracts of Geobacter sulfurreducens catalyzed the NADPH-dependent reduction of Fe(III)-nitrilotriacetic acid (NTA). The responsible enzyme, which was recovered in the soluble protein fraction, was purified to apparent homogeneity in a four-step procedure. Its specific activity for Fe(III) reduction was 65 micromol. min(-1). mg(-1). The soluble Fe(III) reductase was specific for NADPH and did not utilize NADH as an electron donor. Although the enzyme reduced several forms …
Cobra Encodes A Putative Gpi-Anchored Protein, Which Is Polarly Localized And Necessary For Oriented Cell Expansion In Arabidopsis, Tobias Baskin, G. Schindelman, A. Morikami, J. Jung, N.C. Carpita, P. Derbyshire, M.C. Mccann, P.N. Benfey
Cobra Encodes A Putative Gpi-Anchored Protein, Which Is Polarly Localized And Necessary For Oriented Cell Expansion In Arabidopsis, Tobias Baskin, G. Schindelman, A. Morikami, J. Jung, N.C. Carpita, P. Derbyshire, M.C. Mccann, P.N. Benfey
Tobias Baskin
To control organ shape, plant cells expand differentially. The organization of the cellulose microfibrils in the cell wall is a key determinant of differential expansion. Mutations in the COBRA (COB) gene of Arabidopsis, known to affect the orientation of cell expansion in the root, are reported here to reduce the amount of crystalline cellulose in cell walls in the root growth zone. The COB gene, identified by map-based cloning, contains a sequence motif found in proteins that are anchored to the extracellular surface of the plasma membrane through a glycosylphosphatidylinositol (GPI) linkage. In animal cells, this lipid linkage is known …
Development Of A Genetic System For Geobacter Sulfurreducens, Maddalena V. Coppi, Ching Leang, Steven J. Sandler, Derek Lovley
Development Of A Genetic System For Geobacter Sulfurreducens, Maddalena V. Coppi, Ching Leang, Steven J. Sandler, Derek Lovley
Derek Lovley
Members of the genus Geobacter are the dominant metal-reducing microorganisms in a variety of anaerobic subsurface environments and have been shown to be involved in the bioremediation of both organic and metal contaminants. To facilitate the study of the physiology of these organisms, a genetic system was developed forGeobacter sulfurreducens. The antibiotic sensitivity of this organism was characterized, and optimal conditions for plating it at high efficiency were established. A protocol for the introduction of foreign DNA into G. sulfurreducens by electroporation was also developed. Two classes of broad-host-range vectors, IncQ and pBBR1, were found to be capable of replication …
Reductive Presipitation Of Gold By Dissimilatory Fe(Iii)-Reducing Bacteria And Archaea, Kazem Kashefi, Jason M. Tor, Kelly P. Nevin, Derek Lovley
Reductive Presipitation Of Gold By Dissimilatory Fe(Iii)-Reducing Bacteria And Archaea, Kazem Kashefi, Jason M. Tor, Kelly P. Nevin, Derek Lovley
Derek Lovley
Studies with a diversity of hyperthermophilic and mesophilic dissimilatory Fe(III)-reducing Bacteria andArchaea demonstrated that some of these organisms are capable of precipitating gold by reducing Au(III) to Au(0) with hydrogen as the electron donor. These studies suggest that models for the formation of gold deposits in both hydrothermal and cooler environments should consider the possibility that dissimilatory metal-reducing microorganisms can reductively precipitate gold from solution.
Application Of The 5' Fluorogenic Exonuclease Assay (Taqman) For Quantitative Ribosomal Dna And Rrna Analysis In Sediments, Jennie R. Stults, Oona Snoeyenbos-West, Barbara Methѐ, Derek Lovley, Darrell P. Chandler
Application Of The 5' Fluorogenic Exonuclease Assay (Taqman) For Quantitative Ribosomal Dna And Rrna Analysis In Sediments, Jennie R. Stults, Oona Snoeyenbos-West, Barbara Methѐ, Derek Lovley, Darrell P. Chandler
Derek Lovley
In this study, we report on the development of quantitative PCR and reverse transcriptase PCR assays for the 16S rRNA ofGeobacter spp. and identify key issues related to fluorogenic reporter systems for nucleic acid analyses of sediments. The lower detection limit of each assay was 5 to 50 fg of genomic DNA or ≤2 pg of 16S rRNA. TaqMan PCR spectral traces from uncontaminated, amended aquifer sediments were significantly lower (P < 0.0002) than traces for the external standard curve. We also observed a similar, significant decrease in mean quencher emissions for undiluted extracts relative to those for diluted extracts (P < 0.0001). If PCR enumerations were based solely upon the undiluted sample eluant, the TaqMan assay generated an inaccurate result even though the threshold cycle (C t) measurements were precise and reproducible in the sediment extracts. Assay accuracy was significantly improved by employing a system of replicate dilutions and replicate analyses for both DNA and rRNA quantitation. Our results clearly demonstrate that fluorescence quenching and autofluorescence can significantly affect TaqMan PCR enumeration accuracy, with subsequent implications for the design and implementation of TaqMan PCR to sediments and related environmental samples.
Temperature-Sensitive Alleles Of Radially Swollen2 Link The Korrigan Endo-1,4-Fl-Glucanase To Cellulose Synthesis And Cytokinesis, Tobias Baskin, D.R. Lane, A. Wiedemeier, L. Peng, H. H^Fte, C.H. Hocart, R.J. Birch, J.E. Burn, T. Arioli, A.S. Betzner, R.E. Williamson
Temperature-Sensitive Alleles Of Radially Swollen2 Link The Korrigan Endo-1,4-Fl-Glucanase To Cellulose Synthesis And Cytokinesis, Tobias Baskin, D.R. Lane, A. Wiedemeier, L. Peng, H. H^Fte, C.H. Hocart, R.J. Birch, J.E. Burn, T. Arioli, A.S. Betzner, R.E. Williamson
Tobias Baskin
An 8.5-kb cosmid containing the KORRIGAN gene complements the cellulose-deficient rsw2-1 mutant of Arabidopsis. Three temperature-sensitive alleles of rsw2show single amino acid mutations in the putative endo-1,4-β-glucanase encoded by KOR. The F1 from crosses betweenkor-1 and rsw2 alleles shows a weak, temperature-sensitive root phenotype. The shoots ofrsw2-1 seedlings produce less cellulose and accumulate a short chain, readily extractable glucan resembling that reported forrsw1 (which is defective in a putative glycosyltransferase required for cellulose synthesis). The double mutant (rsw2-1 rsw1) shows further reductions in cellulose production relative to both single mutants, constitutively slow root growth, and enhanced temperature-sensitive responses that are …
Temperature-Dependent Oxygen And Carbon Isotopes Fractionations Of Biogenic Siderite, Derek Lovley, Chuanlun L. Zhang, Juske Horita, David R. Cole, Jizhong Zhou, Tommy J. Phelps
Temperature-Dependent Oxygen And Carbon Isotopes Fractionations Of Biogenic Siderite, Derek Lovley, Chuanlun L. Zhang, Juske Horita, David R. Cole, Jizhong Zhou, Tommy J. Phelps
Derek Lovley
Isotopic compositions of biogenic iron minerals may be used to infer environmental conditions under which bacterial iron reduction occurs. The major goal of this study is to examine temperature-dependent isotope fractionations associated with biogenic siderite (FeCO3). Experiments were performed by using both mesophilic (<35°C) and thermophilic (>45°C) iron-reducing bacteria. In addition, control experiments were performed to examine fractionations under nonbiologic conditions. Temperature-dependent oxygen isotope fractionation occurred between biogenic siderite and water from which the mineral was precipitated. Samples in thermophilic cultures (45–75°C) gave the best linear correlation, which can be described as 103 lnαsid-wt = 2.56 × 106 T−2 (K) + 1.69. …
Direct And Indirect Effects Of Alkaloids On Plant Fitness Via Herbivory And Pollination, Lynn Adler, Richard Karban, Sharon Y. Strauss
Direct And Indirect Effects Of Alkaloids On Plant Fitness Via Herbivory And Pollination, Lynn Adler, Richard Karban, Sharon Y. Strauss
Lynn Adler
Herbivores and pollinators can simultaneously exert selective pressures on plant traits via direct and indirect effects. Net selection on plant traits, such as defensive chemistry, may be difficult to predict from studying either of these interactions in isolation. In this study, alkaloids were manipulated experimentally in the hemiparasitic annual plant Castilleja indivisa (Scrophulariaceae; Indian paintbrush) by growing these parasites with bitter (high-alkaloid) or sweet (low-alkaloid) near-isogenic lines of the host Lupinus albus (Fabaceae) in the field. To evaluate the effect of herbivores, half of the Indian paintbrush plants were randomly assigned to a reduced-herbivory treatment using insecticide, and the other …