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Role of the glutamine-dependent acid resistance system of Brucella spp. in response to extreme acid stress
No full textThe Federation of European Microbiological Societies (FEMS) and the Spanish Society for Microbiology (SEM) have joined forces to give you the best of microbiology. Come to the modern and friendly Mediterranean city Valencia, meet fellow microbiologists and update your knowledge with the state of the art on antimicrobial resistance and infections, food microbiology, sustainability, climate change and many more topics.
Key disciplines including molecular approaches, biodiversity, bioremediation, eukaryotic microbes, virology and others will be examined in order to advance our understanding of current and future challenges.Background: The glutamate-dependent decarboxylase (GAD) system is the most potent acid resistance system (AR2) described in Escherichia coli. It consists of a glutamate decarboxylase enzyme and a glutamate/GABA antiporter. Our group showed that the GAD system is also operative in newly described and atypical Brucella species, among which Brucella microti. Recently, an AR2-Q system, based on deamination of glutamine to glutamate by the glutaminase YbaS, was also described in E. coli. In the genome of Brucella, a glsA gene homologous to ybaS is located just upstream and in same orientation as the gadB and gadC genes encoding the GAD system.
Objectives: Using a panel of genus-representative strains, our aim was to demonstrate the existence of a functional AR2-Q system in Brucella spp and its contribution to survival at an extreme acid stress.
Methods and Results: In contrast to the classical Brucella species studied, only the new and atypical strains were found AR in the presence of glutamine and glutamate. By RT-PCR experiments, the genes of the gadBC-glsA locus were found expressed as an operon. Functional complementation of a glsA mutant of B. microti with the ybaS gene of E. coli demonstrated strong homologies between the 2 enzymes. Acid resistance phenotypes of mutant strains of B. microti confirmed the role of the AR2-Q system in extreme glutamine-dependent AR at pH 2.5.
Conclusion: The GAD and AR2-Q systems are functional in new and atypical species of Brucella. This study provides insight into the adaptation of these strains to extremely acidic environments
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Role of the glutamate decarboxylase(GAD)-dependent system of Brucella spp. in the resistance to extreme acid stess
No full textBrucella is the causative agent of brucellosis, the major bacterial zoonosis worldwide. This infection is transmitted to humans primarily by ingestion of contaminated/unpasteurized dairy products. In the last years, new species and atypical strains of Brucella (as B. microti, B. inopinata and isolates from bullfrog) have been isolated. These are more acid-resistant (AR) than the classical Brucella species (as B. abortus, B. melitensis, B. suis). In several food-borne pathogens such as Escherichia coli, the GAD-dependent system is the most efficient for survival under extreme acid stress. Our team has demonstrated that also in B. microti this system allows survival at pH 2.5 and contributes to murine infection by oral route [Occhialini A. et al, 2012].
The existence of a potentially functional GAD system in the new Brucella species, hypothesized by an in silico analysis of their genome sequences, was investigated by bacteriological, biochemical and genetic approaches. In contrast to the classical Brucella species, new and atypical strains were GAD-positive, able to export GABA and AR in the presence of glutamate or glutamine. Functional complementation of an E. coli gad mutant with the gad loci from Brucella strains demonstrated strong homologies between the two systems.
We suggest that a functional GAD system may contribute to improve the adaptability of new species of Brucella in certain natural habitats and/or in the gastrointestinal tract of their hosts [Damiano MA et al. Appl. Environ. Microbiol. 2015]
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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