1,720,968 research outputs found
PCR primers based on different portions of insertion elements can assist phylogeny studies, strain fingerprinting and species identification in rhizobia.
No full textUsing the sequence of an insertion element originally found in Rhizobium sullae, the nitrogen-fixing bacterial symbiont of the legume Hedysarum coronarium, we devised three primer pairs (inbound, outbound and internal primers) for the following applications: (a) tracing genetic relatedness within rhizobia using a method independent of ribosomal inheritance, based on the presence and conservation of IS elements; (b) achieve sensitive and reproducible bacterial fingerprinting; (c) enable a fast and unambiguous detection of rhizobia at the species level. In terms of taxonomy, while in line with part of the 16S rRNA gene- and glutamine synthetase I-based clustering, the tools appeared nonetheless more coherent with the actual geographical ranges of origin of rhizobial species, strengthening the European-Mediterranean connections and discerning them from the asian and american taxa. The fingerprinting performance of the outward-pointing primers, designed upon the inverted repeats, was shown to be at least as sensitive as BOX PCR, and to be functional on a universal basis with all 13 bacterial species tested. The primers designed on the internal part of the transposase gene instead proved highly species-specific for R. sullae, enabling selective distinction from its most related species, and testing positive on every R. sullae strain examined, fulfilling the need of PCR-mediated species identification. A general use of other IS elements for a combined approach to rhizobial taxonomy and ecology is proposed
Novel IS elements-based PCR approaches for species identification and strain fingerprinting in rhizobia and other bacteria
No full textCharacterization of endophytic and symbiotic bacteria within plants of the endemic association Centaureetum horridae Mol.
No full textWe investigated the internal association of bacteria with Astragalus terraccianoi and Centaurea horrida, two endemic plants of the Mediterranean islands, forming the phytosociological association Centaureetum horridae, typical of windswept cliffs on the rocky shores of Asinara (Sardinia, Italy) and other limited locations. Sampling occurred in the protected natural park of the Asinara island. Roots and stems of the two plants and the root nodules of A. terraccianoi were surface sterilized in order to remove external and rhizospheric microbiota and to subsequently isolate the culturable bacterial communities. Plate counts revealed densities of endophytes between 3.7 × 102 and 2.8 × 104 colony forming units per gram of fresh weight. 16S rDNA sequencing revealed the occurrence of bacteria displaying high similarity with Actinobacterium sp., Paenibacillus sp., Rhizobium sp., Methylobacterium sp., Pedobacter panaciterrae, Aerococcus viridans, Stenotrophomonas rhizophila, Bacillus sporothermodurans, Bacillus pumilus, Bacillus simplex, Bacillus flexus, Streptomyces ciscaucasicus and Dyella sp. The putative nitrogen-fixing rhizobium symbiont of A. terraccianoi was identified for the first time. It turned out to belong to the slow-growing Bradyrhizobium genus and to share a 97% similarity with Bradyrhizobium canariense. It was found to be nonculturable and to coexist in nodules with a number of different endophytes
Molecular signals in Pseudomonas tolaasii/Pleurotus eryngii host/pathogen interactions;
No full textP. tolaasii strain P12 has been found in association with brown blotch disease on Pleurotus eryngii, one of the more extensively cultivated mushrooms in the Mediterranean area. Bacterial population density represents a key factor as the infected basidiocarps develop disease symptoms when the pathogen concentration is higher than 104 cfu/g d.w. Virulence of P. tolaasii, mainly due to tolaasin production, may be regulated by quorum sensing (QS) cell-density-dependent regulatory mechanism related to N-acyl homoserine lactones (AHLs). The capacity of P12 to produce AHLs has been investigated. Very low signals related to the production of AHLs were obtained in P12 and other five P. tolaasii strains. Moreover, the capacity to enter the viable but not culturable (VBNC) state was observed under low nutrient anaerobic conditions. As in others bacteria the ability to enter the VBNC state has been associated to the production of QS signals, the above conditions were adopted for QS signal production experiments. Data obtained suggest that specific conditions must be needed to activate QS genes in P12. The involvement of these specific factors in the occurrence of the disease has to be elucidated
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
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