1,720,963 research outputs found
Bacterial Lipodepsipeptides and Some of Their Derivatives and Cyclic Dipeptides as Potential Agents for Biocontrol of Pathogenic Bacteria and Fungi of Agrarian Plants
No full textBiotic stresses (fungi, bacteria, insects, weeds, etc.) are some of the most important causes of the decrease in the quality and quantity of crops that could become an emergency due to a noteworthy increase in the world population. Thus, to overcome these problems, massive use of chemical pesticides has been carried out with heavy consequences for environmental pollution and food safety. An eco-friendly alternative can be using natural compound-based biopesticides with high efficacy and selectivity. Some bacterial lipodepsipeptides (tolaasins I, II, A, D, and E and WLIP together with hexacetyl- and tetrahydro-tolaasin I and WLIP methyl ester) and cyclic dipeptides (cyclo(l-Pro-l-Tyr), cyclo(d-Pro-l-Tyr), cyclo(l-Pro-l-Val), and cyclo(l-Pro-l-Leu)) were assayed against several pathogenic bacteria and fungi of important agrarian plants. Lipodepsipeptides showed strong growth inhibition of all microorganisms tested in the range of 0.1-0.8 μg/mL, while cyclodipeptides, despite preserving this ability, showed a noteworthily reduced antimicrobial activity being active only in the range of 15-900 μg/mL. Among the lipodepsipeptides and cyclic dipeptides assayed, tolaasin d and cyclo(l-Pro-l-Tyr) (also named maculosin-1) appeared to be the most toxic compounds. Some structure-activity relationships of lipodepsipeptides were also discussed along with their practical application as biopesticides in agriculture
The triterpenoid curcumene mediates the relative hydrophilicity of Bacillus subtilis spores
No full text: Spores of Bacillus subtilis are surrounded and protected by the coat and the crust, multi-layered structures mainly made of proteins and polysaccharides. These polysaccharides are covalently linked to some of the coat and crust proteins and influence some spore properties, such as surface adhesion and hydrophilicity. This study reports that a mutant strain lacking the spsA-L operon, encoding 11 enzymes involved in the synthesis of spore surface polysaccharides, produced spores exposing on their surface hydrophobic molecules that were responsible for the drastic reduction of hydrophilicity of the mutant spores. Biochemical and genetic data support the identification of the C35-terpenoid curcumene, a precursor of the spore-associated lipid sporulene, as the highly hydrophobic molecule present on the surface of mutant spores.IMPORTANCEBacterial spores are the most resistant cell forms on Earth. The metabolically quiescent spores withstand conditions that would be lethal for other cells, maintaining the capacity to sense the environment and respond to the presence of favorable conditions by germinating. Such remarkable resistance is also due to the complex layers that surround the spore cytoplasm and protect it against damaging factors. Altogether, the spore surface layers form a complex cell structure composed of proteins, polysaccharides, and, as highlighted by this study, also of lipids. Understanding the complexity of the spore surface and the specific molecules involved in its structure is an essential step for unraveling the mechanisms underlying the spore's resistance to environmental assaults
Structural studies on the O-specific polysaccharide of the lipopolysaccharide from Pseudomonas donghuensis strain SVBP6, with antifungal activity against the phytopathogenic fungus Macrophomina phaseolina
No full textAn O-specific polysaccharide (OPS) was isolated from the lipopolysaccharide (LPS) of Pseudomonas donghuensis SVBP6, a bacterium with a broad-spectrum antifungal activity in vitro, particularly that against Macrophomina phaseolina. This latter is one of the most virulent and dangerous pathogens of plants, including soybean which is an economically important crop in Argentina today. The OPS was studied by sugar analysis and spectroscopy (1D and 2D 1H and 13C NMR) showing the following trisaccharide repeating unit: →6)-ɑ-D-ManpNAc-(1 → 3)-β-L-Rhap-(1 → 4)-β-D-Glcp-(1→. The crude LPS, the purified LPS and the O-chain were assayed for their antifungal activity against M. phaseolina at 25, 50, 100, and 200 μg plug−1. The results showed that the crude LPS best inhibition was at 200 μg plug−1, able to inhibit the fungus growth by about 45%, while purified LPS and the corresponding OPS, in the same condition, reduced fungus growth by 65%, and 75%, respectively. Furthermore, the purified LPS and OPS significantly reduced the growth of M. phaseolina already at 100 μg plug−1 compared to the crude LPS. The structure of the O-chain is unique among the bacterial LPS and this is the first time that both the antifungal activity of a bacterial LPS and its corresponding O-chain were described.Fil: Zdorovenko, Evelina L.. Università degli Studi di Napoli Federico II; ItaliaFil: Dmitrenok, Andrey S.. Università degli Studi di Napoli Federico II; ItaliaFil: Masi, Marco. Università degli Studi di Napoli Federico II; ItaliaFil: Castaldi, Stefany. Università degli Studi di Napoli Federico II; ItaliaFil: Muzio, Federico Matías. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Isticato, Rachele. Università degli Studi di Napoli Federico II; ItaliaFil: Valverde, Claudio Fabián. Universidad Nacional de Quilmes; ArgentinaFil: Knirel, Yuriy A.. Università degli Studi di Napoli Federico II; ItaliaFil: Evidente, Antonio. Università degli Studi di Napoli Federico II; Itali
Use of halotolerant Bacillus amyloliquefaciens RHF6 as a bio-based strategy for alleviating salinity stress in Lotus japonicus cv Gifu
No full text: Halotolerant (HT) bacteria are a group of microorganisms able to thrive in environments with relatively high salt concentrations. HT-microorganisms with plant growth-promoting (PGP) characteristics have been proposed to increase plant tolerance in salty soil. Here, we evaluated the PGP properties at increasing NaCl concentrations of HT-Bacillus strains, previously shown to have beneficial effects under physiological conditions. Most of the isolated showed indole acetic acid and ammonia production and were able to solubilize phosphate and suppress the proliferation of the phytopathogenic fungus Macrophomina phaseolina 2013-1 at high salt concentrations. One of the selected strains, Bacillus amyloliquefaciens RHF6, which retained its beneficial properties up to 400 mM NaCl in vitro, was tested on the legume model plant Lotus japonicus cv Gifu under salt stress. The inoculation with RHF6 significantly improved the survival of plants under high salinity conditions, as reflected in seedling root and shoot growth and total fresh weight (increased by 40%) when compared with non-inoculated plants. The ability of RHF6 to induce a plant antioxidant response, secrete the osmoprotectant proline and reduce ethylene level via the enzymatic ACC deaminase activity indicated this strain as a potentially helpful PGPB for the treatment of degraded soils
Truncatenolide, a Bioactive Disubstituted Nonenolide Produced by Colletotrichum truncatum, the Causal Agent of Anthracnose of Soybean in Argentina: Fungal Antagonism and SAR Studies
No full text[Image: see text] A bioactive disubstituted nonenolide, named truncatenolide, was produced by Colletotrichum truncatum, which was collected from infected tissues of soybean showing anthracnose symptoms in Argentina. This is a devastating disease that drastically reduces the yield of soybean production in the world. The fungus also produced a new trisubstituted oct-2-en-4-one, named truncatenone, and the well-known tyrosol and N-acetyltyramine. Truncatenolide and truncatenone were characterized by spectroscopic (essentially one-dimensional (1D) and two-dimensional (2D) (1)H and (13)C NMR and HR ESIMS) and chemical methods as (5E,7R,10R)-7-hydroxy-10-methyl-3,4,7,8,9,10-hexahydro-2H-oxecin-2-one and (Z)-6-hydroxy-3,5-dimethyloct-2-en-4-one, respectively. The geometry of the double bond of truncatenolide was assigned by the value of olefinic proton coupling constant and that of truncatenone by the correlation observed in the corresponding NOESY spectrum. The relative configuration of each stereogenic center was assigned with the help of (13)C chemical shift and (1)H–(1)H scalar coupling DFT calculations, while the absolute configuration assignment of truncatenolide was performed by electronic circular dichroism (ECD). When tested on soybean seeds, truncatenolide showed the strongest phytotoxic activity. Tyrosol and N-acetyltyramine also showed phytotoxicity to a lesser extent, while truncatenone weakly stimulated the growth of the seed root in comparison to the control. When assayed against Macrophomina phaseolina and Cercospora nicotianae, other severe pathogens of soybean, truncatenolide showed significant activity against M. phaseolina and total inhibition of C. nicotianae. Thus, some other fungal nonenolides and their derivatives were assayed for their antifungal activity against both fungi in comparison with truncatenolide. Pinolidoxin showed to a less extent antifungal activity against both fungi, while modiolide A selectively and totally inhibited only the growth of C. nicotianae. The SAR results and the potential of truncatenolide, modiolide A, and pinolidoxin as biofungicides were also discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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