1,720,971 research outputs found
GAINING INSIGHTS IN THE MICROBIAL DEGRADATION OF POLYETHYLENE PLASTICS
No full textIl polietilene (PE) rappresenta più del 60% di tutte le plastiche derivate dal petrolio a livello mondiale, e si sta accumulando ad un tasso di diversi milioni di tonnellate per anno a causa della sua riluttanza alla degradazione biotica e abiotica. La degradazione microbica è stata proposta come possibile strada alternativa nella riduzione dei rifiuti plastici.
Lo scopo generale di questo lavoro è stata l'identificazione di ceppi batterici in grado di metabolizzare il PE e di identificare le vie metaboliche coinvolte in tale processo di biodegradazione.
Abbiamo analizzato mediante approccio metagenomico diversi campioni di plastica raccolti in una discarica abbandonata, ed è stata scoperta una forte relazione tra le proprietà della plastica (inclusa la presenza di coloranti) e la comunità microbica
Analizzando la comunità microbica esposta al PE nell’ ambiente, abbiamo isolato 10 ceppi batterici in grado di crescere utilizzando il PE come unica fonte di energia e di carbonio.
Uno di questi ceppi, Pseudomonas aeruginosa UC4003, ha mostrato la più alta capacità di crescere in terreno minimo e polietilene. Quando cresce su PE, questo ceppo produce un enzima extracellulare, proteina-attivatore per l’ossidazione degli n-alcani (PA), coinvolto nelle prime fasi di degradazione di polietilene.Plastics production, use and degradation are hot topics that have come to the forefront over recent years. Polyethylene (PE) represents more than 60% of all petroleum-derived plastics worldwide and is accumulating at rates of several millions of tons per year because of its strong recalcitrance to biotic and abiotic degradation. Microbial degradation has been proposed as a possible alternative way to reduce plastic wastes.
The general aim of this work was the identification of bacterial strains able to metabolize PE and to identify the biochemical pathways of this biodegradation process.
In an abandoned landfill we collected different plastic samples; using a metagenomic approach, we found a strong relationship between the plastic properties (including the presence of colorants) and the microbial community
By screening the natural microbial community exposed to PE in environment, we isolated 10 bacteria which revealed the ability to grow on PE as only energy and carbon source.
A bacterium, Pseudomonas aeruginosa UC4003, showed the highest growth rate in minimal salt medium and polyethylene. When grown on PE, this strain produced an extracellular enzyme, protein-like activator for n-alkane oxidation (PA), involved in the first step of polyethylene degradation
Selective colonization processes of plastic-loving bacteria in an abandoned landfill site
No full textPolyethylene (PE), the most common petroleum-based plastic, is strongly recalcitrant to degradation. Despite this, recent evidences showed that a few microbial strains can partially degrade PE pre-oxidized by abiotic processes.
Here, we investigated plastic samples from an abandoned landfill, with the aim of elucidating the ecology of soil microorganisms able to grow on the plastics and to correlate them with plastic degradation levels.
Isolations were carried after detachment of the biofilm from the plastic surfaces and se- rial dilutions on selective agar plates of mineral medium with paraffin as the only carbon source. Microbial DNA derived from the plastic surfaces, the landfill soil and an uncontam- inated neighboring agricultural soil was also analyzed by Illumina sequencing of 16S rRNA amplicons.
A total of 49 strains growing on paraffin were identified: the most representative genus is Bacillus genus with 12 different species represented, followed by Pseudomonas, Lysini- bacillus, Comanomonas and Acinetobacter.
Differential scanning calorimetric analysis of the plastic samples showed an additional shoul- der melting peak with various enthalpies besides the main melting peak, implying the plastic exhibited different degrees of degradation. In parallel, Illumina 16S rRNA analyses showed that the different plastics hosted different microbial communities, and that the bacterial community derived from plastic sample with the highest degradation level was the most similar to that of the soil derived from contaminated landfill. Results point to an interesting correlation between the level of plastic degradation and the composition of the microbial biofilm
Selective bacterial colonization processes on polyethylene waste samples in an abandoned landfill site
Full text linkThe microbial colonization of plastic wastes has been extensively studied in marine environments, while studies on aged terrestrial wastes are scarce, and mostly limited to the isolation of plastic-degrading microorganisms. Here we have applied a multidisciplinary approach involving culturomics, next-generation sequencing analyses and fine-scale physico-chemical measurements to characterize plastic wastes retrieved in landfill abandoned for more than 35 years, and to assess the composition of bacterial communities thriving as biofilms on the films’ surfaces. All samples were characterized by different colors but were all of polyethylene; IR and DSC analyses identified different level of degradation, while FT-Raman spectroscopy and X-ray fluorescence further assessed the degradation level and the presence of pigments. Each plastic type harbored distinct bacterial communities from the others, in agreement with the differences highlighted by the physico-chemical analyses. Furthermore, the most degraded polyethylene films were found to host a bacterial community more similar to the surrounding soil as revealed by both α- and β-diversity NGS analyses. This work confirms the novel hypothesis that different polyethylene terrestrial waste samples select for different bacterial communities, and that structure of these communities can be correlated with physico-chemical properties of the plastics, including the degradation degree
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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