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  • 1
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    Microbial oxidative sulfur metabolism: biochemical evidence of the membrane-bound heterodisulfide reductase-like complex of the bacterium Aquifex aeolicus (2016)
    Oxford University Press
    Details
    Publication Date: 2016-07-03
    Description: The Hdr (heterodisulfide reductase)-like enzyme is predicted, from gene transcript profiling experiments previously published, to be essential in oxidative sulfur metabolism in a number of bacteria and archaea. Nevertheless, no biochemical and physicochemical data are available so far about this enzyme. Genes coding for it were identified in Aquifex aeolicus , a Gram-negative, hyperthermophilic, chemolithoautotrophic and microaerophilic bacterium that uses inorganic sulfur compounds as electron donor to grow. We provide biochemical evidence that this Hdr-like enzyme is present in this sulfur-oxidizing prokaryote (cultivated with thiosulfate or elemental sulfur). We demonstrate, by immunolocalization and cell fractionation, that Hdr-like enzyme is associated, presumably monotopically, with the membrane fraction. We show by co-immunoprecipitation assay or partial purification, that the Hdr proteins form a stable complex composed of at least five subunits, HdrA, HdrB1, HdrB2, HdrC1 and HdrC2, present in two forms of high molecular mass on native gel (~240 and 450 kDa). These studies allow us to propose a revised model for dissimilatory sulfur oxidation pathways in A. aeolicus , with Hdr predicted to generate sulfite.
    Keywords: Physiology & Biochemistry
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 2
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    Determinants of Occupational Safety for Agribusiness Workers (2014)
    Oxford University Press
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    Publication Date: 2014-09-06
    Description: Increases in crop yields and changing cropping patterns have placed stress on agribusiness handling and storage facilities. The objective of this research is to gain insight into the relationship between safety culture and safety performance, and to identify the determinants of safety culture in agribusinesses. The research suggests that investments in labor inputs such as increased training, consistent discipline, and recognition of safety achievements all increase safety culture. Furthermore, improvements in employee perceptions of safety culture have a positive impact on reducing employee injuries. Congress has recently funded nine centers to work on occupational health and safety research in agriculture, fisheries, and forestry.
    Keywords: J43 - Agricultural Labor Markets, L66 - Food ; Beverages ; Cosmetics ; Tobacco ; Wine and Spirits, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by Oxford University Press
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  • 3
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    D-serine transporter in Staphylococcus saprophyticus identified (2016)
    Oxford University Press
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    Publication Date: 2016-06-23
    Description: Among staphylococci Staphylococcus saprophyticus is the only species that is typically uropathogenic and an important cause of urinary tract infections in young women. The amino acid D-serine occurs in relatively high concentrations in human urine and has a bacteriostatic or toxic effect on many bacteria. In uropathogenic Escherichia coli and S. saprophyticus , the amino acid regulates the expression of virulence factors and can be used as a nutrient. The ability of uropathogens to respond to or to metabolize D-serine has been suggested as a factor that enables colonization of the urinary tract. Until now nothing is known about D-serine transport in S.   saprophyticus . We generated mutants of putative transporter genes in S.   saprophyticus 7108 that show homology to the D-serine transporter cyc A of E. coli and tested them in a D-serine depletion assay to analyze the D-serine uptake rate of the cells. The mutant of SPP1070 showed a strong decrease in D-serine uptake. Therefore, SSP1070 was identified as a major D-serine transporter in S. saprophyticus 7108 and was named D-serine transporter A (DstA). D-serine caused a prolonged lag phase of S. saprophyticus in a chemically defined medium. This negative effect was dependent on the presence of DstA.
    Keywords: Physiology & Biochemistry
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 4
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    Following Up on Smallholder Farmers and Supermarkets in Kenya (2015)
    Oxford University Press
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    Publication Date: 2015-07-10
    Description: In many developing countries, supermarkets are expanding rapidly. This affects farmers’ marketing options. Previous studies have analyzed welfare effects of smallholder participation in supermarket channels from a static perspective, using cross-section data. We develop a conceptual framework and use panel data to better understand participation and impact dynamics. The analysis focuses on vegetable producers in Kenya. Participation in supermarket channels is associated with income gains. However, many farmers have dropped out of the supermarket channel due to various constraints. The initial income gains cannot be sustained when returning to the traditional market. Organizational support may be needed to avoid widening income disparities.
    Keywords: L24 - Contracting Out ; Joint Ventures ; Technology Licensing, O12 - Microeconomic Analyses of Economic Development, O13 - Agriculture ; Natural Resources ; Energy ; Environment ; Other Primary Products, Q12 - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by Oxford University Press
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  • 5
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    CrAgDb--a database of annotated chaperone repertoire in archaeal genomes (2016)
    Oxford University Press
    Details
    Publication Date: 2016-03-02
    Description: Chaperones are a diverse class of ubiquitous proteins that assist other cellular proteins in folding correctly and maintaining their native structure. Many different chaperones cooperate to constitute the ‘proteostasis’ machinery in the cells. It has been proposed earlier that archaeal organisms could be ideal model systems for deciphering the basic functioning of the ‘protein folding machinery’ in higher eukaryotes. Several chaperone families have been characterized in archaea over the years but mostly one protein at a time, making it difficult to decipher the composition and mechanistics of the protein folding system as a whole. In order to deal with these lacunae, we have developed a database of all archaeal chaperone proteins, CrAgDb ( C haperone r epertoire in A rchaeal g enomes). The data have been presented in a systematic way with intuitive browse and search facilities for easy retrieval of information. Access to these curated datasets should expedite large-scale analysis of archaeal chaperone networks and significantly advance our understanding of operation and regulation of the protein folding machinery in archaea. Researchers could then translate this knowledge to comprehend the more complex protein folding pathways in eukaryotic systems. The database is freely available at http://14.139.227.92/mkumar/cragdb/ .
    Keywords: Physiology & Biochemistry
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 6
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    RNA transcript sequencing reveals inorganic sulfur compound oxidation pathways in the acidophile Acidithiobacillus ferrivorans (2016)
    Oxford University Press
    Details
    Publication Date: 2016-03-24
    Description: Acidithiobacillus ferrivorans is an acidophile implicated in low-temperature biomining for the recovery of metals from sulfide minerals. Acidithiobacillus ferrivorans obtains its energy from the oxidation of inorganic sulfur compounds, and genes encoding several alternative pathways have been identified. Next-generation sequencing of At. ferrivorans RNA transcripts identified the genes coding for metabolic and electron transport proteins for energy conservation from tetrathionate as electron donor. RNA transcripts suggested that tetrathionate was hydrolyzed by the tetH1 gene product to form thiosulfate, elemental sulfur and sulfate. Despite two of the genes being truncated, RNA transcripts for the SoxXYZAB complex had higher levels than for thiosulfate quinone oxidoreductase ( doxDA genes). However, a lack of heme-binding sites in soxX suggested that DoxDA was responsible for thiosulfate metabolism. Higher RNA transcript counts also suggested that elemental sulfur was metabolized by heterodisulfide reductase ( hdr genes) rather than sulfur oxygenase reductase ( sor ). The sulfite produced as a product of heterodisulfide reductase was suggested to be oxidized by a pathway involving the sat gene product or abiotically react with elemental sulfur to form thiosulfate. Finally, several electron transport complexes were involved in energy conservation. This study has elucidated the previously unknown At. ferrivorans tetrathionate metabolic pathway that is important in biomining.
    Keywords: Physiology & Biochemistry
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 7
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    Making Sustainability Tangible: Land O'Lakes and the Dairy Supply Chain (2016)
    Oxford University Press
    Details
    Publication Date: 2016-03-31
    Description: This case study examines the challenges of implementing a vaguely defined concept called sustainability in a large organization that also has a cooperative structure. Stakeholder theory is described and applied to a multinational dairy firm. The case firm, Land O'Lakes, must balance the needs of multiple constituencies: the general public, employees, cooperative members, external funding organizations, and the management team. One challenge is to define sustainability for the entire dairy industry. The case discusses the strategies used by firms in developing a sustainability response where the tradeoffs between different strategies are between credibility and autonomy and using an industry rather than a firm-level response.
    Keywords: L15 - Information and Product Quality ; Standardization and Compatibility, L66 - Food ; Beverages ; Cosmetics ; Tobacco ; Wine and Spirits, M14 - Corporate Culture ; Social Responsibility, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by Oxford University Press
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  • 8
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    Lipoprotein-like particles in a prokaryote: quinone droplets of Thermoplasma acidophilum (2016)
    Oxford University Press
    Details
    Publication Date: 2016-09-09
    Description: Cytosolic, globular droplets with an average diameter of 50 nm were observed in vitrified Thermoplasma acidophilum cells by means of cryo-electron tomography. These droplets were isolated by column chromatography and immunoprecipitation protein purification methods. Subsequent chemical and biochemical analyses identified lipid and protein components, respectively. Two major lipid components, comigrating menaquinones at the solvent front and the slower migrating Thermoplasma polar lipid U4, were detected by TLC experiments. The major protein component was identified as the 153 amino acid long Ta0547 vitellogenin-N domain protein. This domain has been found so far exclusively in large lipid transport proteins of vertebrates and non-vertebrates. Blast protein database homology searches with Ta0547 did not return any eukaryal hits; homologous sequences were found only in thermo-acidophilic archaeons. However, a profile-sequence domain search performed with the vitellogenin-N domain (PF01347) hmm-profile against the T. acidophilum proteome returned Ta0547 as hit. Electron microscopy appearance of isolated droplets resembled to lipoprotein particles. However, no (tetraether) lipid layer could be detected on the droplets surface, rather hydrophobic compounds of the electron dense lumen were surrounded by a denser discontinuous protein boundary. Based on described features, these particles qualify for a novel lipoprotein particle category, what we nominated Thermoplasma Quinone Droplet.
    Keywords: Physiology & Biochemistry
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 9
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    Impact of Third-party Contract Enforcement in Agricultural Markets--A Field Experiment in Vietnam (2014)
    Oxford University Press
    Details
    Publication Date: 2014-07-23
    Description: We study the effect of alleviating the information asymmetry regarding product quality that is widespread in contracts between agricultural producers and buyers in developing countries. Opportunistic buyers may underreport quality levels to farmers to reduce the price that they have to pay. In response, farmers may curb investment, thereby negatively affecting farm productivity. In an experiment, we entitle randomly selected smallholder dairy farmers in Vietnam, who are contracted by a large company, to independently verify milk testing results. Results indicate that treatment farmers use 12% more inputs, and they also increase their output significantly. Some wider research and policy implications are discussed.
    Keywords: C93 - Field Experiments, D82 - Asymmetric and Private Information, O13 - Agriculture ; Natural Resources ; Energy ; Environment ; Other Primary Products, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by Oxford University Press
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  • 10
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    A Framework to Analyze the Performance of Thinly Traded Agricultural Commodity Markets (2016)
    Oxford University Press
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    Publication Date: 2016-03-31
    Description: Thinly traded agricultural commodity markets are a concern for farmers and policy markers due to the belief that prices in these settings will be highly volatile, subject to manipulation, and incapable of efficiently allocating resources. Analysis of thin agricultural markets has to date been impeded by lack of an appropriate analytical framework from which to study their behavior. In this paper we propose the modern agricultural markets (MAM) framework as an appropriate paradigm through which to view and evaluate thin markets. We argue that thinly traded markets that meet key conditions required for a MAM will generate maximum economic surplus and enable farmers to earn at least a competitive return on their investments. In the absence of these conditions, however, the concerns known as the "thin market problem" have validity. We set forth the MAM framework, interpret it in a thin-market context, and conduct several brief case studies of thin markets to illustrate use of the approach and draw some key inferences about these markets' behavior. The analysis indicates that appropriate government policies directed to thin markets are those that facilitate their convergence to MAM status, but in reality key policies under recent consideration would have the opposite effect.
    Keywords: L10 - General, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by Oxford University Press
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