1,720,962 research outputs found
Inhibitory Mechanisms by Chlorobenzoate Mixtures in Chlorobenzoate-degrading Microorganisms
No full textA microbial consortium selected on 2-chlorobenzoate was shown to be able to also utilise 4-chlorobenzoate and 2,5-dichlorobenzoate as sole carbon source. The consortium adapted to grow on 4-chlorobenzoate, degraded the carbon source via protocatechuate, whereas the same consortium degraded 2-chlorobenzoate and 2,5-dichlorobenzoate via 1,2- or 1,6-dioxygenation of the chlorinated ring. Moreover, no significant effects on the microbial growth due to the presence of chlorobenzoate mixtures were observed when 4-chlorobenzoate was the carbon source. Instead, when meta-substituted chlorobenzoates were added as co-substrates to 2,5-dichlorobenzoate, the growth of the consortium was totally inhibited, just as when the culture utilised for growth 2-chlorobenzoate. Uptake experiments with 2-chlorobenzoate-grown resting cells showed that 3-chlorobenzoate, 2,3-dichlorobenzoate and 2,3,5-trichlorobenzoate competed with 2-chlorobenzoate, entering the resting cells both preferentially and faster than the growth substrate, that was also impeded to enter. Also 3,4-dichlorobenzoate and 3,5-dichlorobenzoate hindered the uptake of the growth substrate (2-chlorobenzoate and 2,5-dichlorobenzoate, respectively), but they did not enter themselves the cells. Finally, 3,5-dichlorobenzoate neither entered the 4-chlorobenzoate-grown cells nor hindered 4-chlorobenzoate uptake. The relationships between growth inhibiting effects and chlorosubstituent position on the aromatic ring of the chlorobenzoates supplied as co-substrates are discussed
Metabolismo microbico
No full textIl termine metabolismo definisce l’insieme delle reazioni chimiche che si svolgono a livello cellulare e che sono necessarie alla vita dei microrganismi. Il metabolismo può essere considerato suddiviso in due fasi, tra loro strettamente interdipendenti: il catabolismo, comprendente le reazioni chimiche che portano alla produzione di energia, e l’anabolismo, comprendente le reazioni endoergoniche che portano alla sintesi delle macromolecole complesse a partire da composti semplici (precursori metabolici). Se l’anabolismo è per molti aspetti abbastanza simile nei procarioti e negli eucarioti, il catabolismo nei batteri presenta una varietà di meccanismi implicati nella conservazione dell’energia, che li rende paragonabili a “catalizzatori biologici”, capaci di innumerevoli reazioni e trasformazioni. Questo aspetto della vita microbica rende i procarioti responsabili dei cicli biologici dei principali elementi, che condizionano la vita sulla terra
Chlorophenol removal from soil suspensions : effects of a specialised microbial inoculum and a degradable analogue
No full textTwo soils of different contamination history were tested in slurry for their self-remediability towards mono-, diand trisubstituted chlorophenols. The landfill soil showed poor ability in removing the compounds. Instead, the soil from the golf course, treated for many years with a 2,4,6-trichlorophenol derivative (Prochloraz), remediated different concentrations of the same 2,4,6TCP, 2,4-dichlorophenol and monochlorophenol isomers, singly and in mixtures, at varying degradation rates. Ralstonia eutropha TCP, a specialised microorganism capable of degrading 2,4,6TCP, proved highly efficient in removing the compound from both tested soils. The same microbial inoculum allowed total removal of the ternary mixture of monochlorophenol isomers from the golf course soil, but it did not accelerate the removal of the same compounds when singly supplied. The addition of phenol as a degradable analogue was more effective in co-metabolically removing not only the single monochlorophenols,but also their mixtures, the removal occurring faster and independently of the presence of the microbial inoculum. From the golf course soil, a microorganism, phenotypically and genetically identical to R. eutropha TCP, was isolated and classified as R. eutropha TCP II
Co-metabolic degradation of mixtures of monochlorophenols by phenol-degrading microorganism
No full textTwo phenol-degrading organisms, Ralstonia eutropha TCP and a Pseudomonas aeruginosa strain, were studied for their co-metabolic capabilities towards chlorophenol (CP) isomers at different substitution grade. R. eutropha TCP resting cells, grown on different substrates, oxidised to varying degrees and regardless the growth substrate, some CP, while the dechlorinating activity/ies of the strain was/were repressed when grown on glutamate. 4MCP was co-metabolised via meta-fission of the aromatic nucleus with the formation of a product with the same spectrophotometric features of 5-chloro-2-hydroxymuconic semialdehyde. The co-metabolites of 2,6-dichlorophenol (2,6DCP) and 2,3,6-trichlorophenol (2,3,6TCP), not yet identified, are probably related to hydroxylated derivatives of the parent CP and/or their condensation products. The growth of R. eutropha TCP was differently affected by the presence of CPs depending on CP type and concentration. After an initial exposure to monochlorophenol (MCP) isomers at 10 mg 1-1 the strain succeeded in tolerating up to 30 mg 1-1 of 2MCP and 50 mg 1-1 of 3- and 4MCP. Viable counts, on comparison with those of other isomers, confirmed the highest toxicity of 2MCP towards R. eutropha TCP adapted cells. However, the organism was capable of totally degrading all the three MCPs, each at 10 mg 1-1, also in binary and ternary combinations in mixture with phenol (POH). P. aeruginosa totally degraded 3- and 4MCP, both singly and in mixture, when supplied at 25 mg 1-1. Differently from R. eutropha TCP, this strain did not cometabolise 2MCP which remained in the cultural broths without inhibiting microbial activities
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
Effects of the herbicide molinate on the metabolic activities of a degradative Streptomyces griseus strain
No full textCometabolic degradation of the herbicide molinate was tested using two microorganisms, Arthrobacter sp., strain M3 and Streptomyces griseus strain M2; the latter classified on the basis of the presence of the enzymatic cofactor SF-420. The strains M3 and M2, inoculated in a basic salts medium with glucose as carbon source and added with 100 mg L(-1) of molinate, degraded respectively 35 and 51% of the herbicide in 36 days.
Increasing concentrations of molinate, ranging from 50 to 200 mg L(-1) in glucose medium, did not affect the final ATP yield ofthe strain M2, but decreased the final growth yield and the ATP synthesis rate. Moreover, the onset of coenzyme SF-420 synthesis was progressively delayed.
In contrast, surprisingly, SF-420 final yield and production rate were increased by progressive increasing concentrations of molinate in the mineral mediu
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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