1,720,977 research outputs found
PCR-genotyping of cyanobacteria from Roman hypogea biofilms and their associated bacteria
No full textEpilithic phototrophic biofilms develop inside Roman Necropolis and Catacombs on rock surfaces exposed to artificial light sources and are composed by a microbial consortium dominated by cyanobacteria. In this work, six non-axenic cultures of Leptolyngbya sp. strains isolated frombiofilms from different Romanhypogea and maintained in cultures from 11 to 20 years were analysed along with their associated bacteria isolated in culture. The employment of PCR-fingerprinting techniques, using HIP1 and ERIC derived primers, allowed the clustering in three groups of the six Leptolyngbya strains and the typing of their isolated bacteria. The bacterial fingerprinting patterns were in agreement with the 16S rRNA gene sequencing and showed the presence in Leptolyngbya isolates of Pseudomonas, Stenotrophomonas, Agrobacterium and Bacillus representatives that were detected also in biofilms sampled from catacombs
A study for monitoring and conservation in the Roman Catacombs of St. Callistus and Domitilla, Rome (Italy).
No full textEffects of biocide treatments on the biofilm community in Domitilla's catacombs in Rome.
No full textDifferent types of biofilms are widespread on lithic faces of the Catacombs of Domitilla (Rome, Italy) due to the
favorable microclimatic conditions (temperature, high RH% and low irradiance). The biofilm, once established,
becomes particularly dangerous due to the coverage of valuable surfaces causing spoilage, softening of materials
and mineral precipitation. It is common practice to treat these surfaceswith biocides in order to eradicate the microorganisms
present. The aim of the present research was to compare the changes occurring to the microbial
community present in the biofilm in one site of the Catacombs of Domitilla (CD15) before and after a biocide
treatment (a mixture of quaternary ammonium compounds and octylisothiazolone, OIT), applied for a one
month period. A multistep approach was followed, based on microscopy, cultural methods and molecular techniques
(f-ITS and 16S rDNA sequencing), for the phenotypic and genetic analysis of the culturable microbial population.
Our results highlighted that the biocide treatments had little effect against cyanobacteria, while the
bacterial population increased in numbers but changed drastically in terms of diversity. In fact, some bacteria
proliferate at the expense of the organic matter released by dead microorganisms as demonstrated by laboratory
tests. Further, our data describe howthe microbial interaction can have different responses depending on the favorable
conditions for one kind of microorganism in respect to the others.
This study exemplifies the real risks of applying biocide treatments on complex microbial communities and pinpoints
the necessity of subjecting treatments to monitoring and reassessment. Moreover, the work showed the potential of bacteria isolated after the treatment for use, under controlled conditions, in combatting unwanted
microbial growth in that they possess a positive tropismtoward stressed microorganisms and high hydrolytic enzymatic
activity against cell components (e.g. cellulose, chitin and pectin). A tentative protocol is proposed
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
Recent Advances in the Application of Metal Oxide Nanomaterials for the Conservation of Stone Artefacts, Ecotoxicological Impact and Preventive Measures
No full textVariations 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
Methodological approaches to the control of phototrophic biofilms colonizing subterranean sites in the Mediterranean area
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