1,720,987 research outputs found
Acinetobacter baumannii biofilm formation in Human serum and disruption by gallium
Full text linkBiofilm-associated infections caused by Acinetobacter baumannii are extremely recalcitrant to antibiotic treatment. We report that A. baumannii develops a mature biofilm when grown in complement-free human serum (HS). We demonstrate that 16 μM gallium nitrate (GaN) drastically reduces A. baumannii growth and biofilm formation in HS, whereas 64 μM GaN causes massive disruption of preformed A. baumannii biofilm. These findings pave the way to the repurposing of GaN as an antibiofilm agent for A. baumannii
Cell aggregation promotes pyoverdine-dependent iron uptake and virulence in Pseudomonas aeruginosa
Full text linkIn Pseudomonas aeruginosa the Gac signaling system and the second messenger cyclic diguanylate (c-di-GMP) participate in the control of the switch between planktonic and biofilm lifestyles, by regulating the production of the two exopolysaccharides Pel and Psl. The Gac and c-di-GMP regulatory networks also coordinately promote the production of the pyoverdine siderophore, and the extracellular polysaccharides Pel and Psl have recently been found to mediate c-di-GMP-dependent regulation of pyoverdine genes. Here we demonstrate that Pel and Psl are also essential for Gac-mediated activation of pyoverdine production. A pel psl double mutant produces very low levels of pyoverdine and shows a marked reduction in the expression of the pyoverdine-dependent virulence factors exotoxin A and PrpL protease. While the exopolysaccharide-proficient parent strain forms multicellular planktonic aggregates in liquid cultures, the Pel and Psl-deficient mutant mainly grows as dispersed cells. Notably, artificially induced cell aggregation is able to restore pyoverdine-dependent gene expression in the pel psl mutant, in a way that appears to be independent of iron diffusion or siderophore signaling, as well as of recently described contact-dependent mechanosensitive systems. This study demonstrates that cell aggregation represents an important cue triggering the expression of pyoverdine-related genes in P. aeruginosa, suggesting a novel link between virulence gene expression, cell-cell interaction and the multicellular community lifestyle
Serotype and clonal evolution of penicillin-nonsusceptible invasive Streptococcus pneumoniae in the 7-valent pneumococcal conjugate vaccine era in Italy.
No full textThe percentage of invasive penicillin-nonsusceptible pneumococci (PNSSP) isolated
in Italy in the seven-valent pneumococcal conjugate vaccine (PCV7) era moderately
increased in comparison to the pre-PCV7 era. Increase of nonvaccine serotypes was
observed among PNSSP. The most frequent PNSSP clones were the same as those
identified in the pre-PCV7 era, although they were present in different
proportions. Clonal expansion, emergence of new clones, and acquisition of
penicillin resistance by established clones contributed to the maintenance of
penicillin resistance
Genome diversity of domesticated Acinetobacter baumannii ATCC 19606T strains
Full text link: Acinetobacter baumannii has emerged as an important opportunistic pathogen worldwide, being responsible for large outbreaks for nosocomial infections, primarily in intensive care units. A. baumannii ATCC 19606T is the species type strain, and a reference organism in many laboratories due to its low virulence, amenability to genetic manipulation and extensive antibiotic susceptibility. We wondered if frequent propagation of A. baumannii ATCC 19606T in different laboratories may have driven micro- and macro-evolutionary events that could determine inter-laboratory differences of genome-based data. By combining Illumina MiSeq, MinION and Sanger technologies, we generated a high-quality whole-genome sequence of A. baumannii ATCC 19606T, then performed a comparative genome analysis between A. baumannii ATCC 19606T strains from several research laboratories and a reference collection. Differences between publicly available ATCC 19606T genome sequences were observed, including SNPs, macro- and micro-deletions, and the uneven presence of a 52 kb prophage belonging to genus Vieuvirus. Two plasmids, pMAC and p1ATCC19606, were invariably detected in all tested strains. The presence of a putative replicase, a replication origin containing four 22-mer direct repeats, and a toxin-antitoxin system implicated in plasmid stability were predicted by in silico analysis of p1ATCC19606, and experimentally confirmed. This work refines the sequence, structure and functional annotation of the A. baumannii ATCC 19606T genome, and highlights some remarkable differences between domesticated strains, likely resulting from genetic drift
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
Microscopy Direct Escherichia coli Live/Dead Cell Counting
No full textWe propose an accurate automated image processing suitably developed for Escherichia coli direct cell counting. We use two fluorescent dyes to discriminate live/dead bacteria and confocal microscopy single-cell analysis
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
Expanding the microbiologist toolbox via new far-red-emitting dyes suitable for bacterial imaging
No full text: By harnessing the versatility of fluorescence microscopy and super-resolution imaging, bacteriologists explore critical aspects of bacterial physiology and resolve bacterial structures sized beyond the light diffraction limit. These techniques are based on fluorophores with profitable photochemical and tagging properties. The paucity of available far-red (FR)-emitting dyes for bacterial imaging strongly limits the multicolor choice of bacteriologists, hindering the possibility of labeling multiple structures in a single experiment. The set of FR fluorophores characterized in this study expands the palette of dyes useful for microbiologists, as they can be used for bacterial LIVE/DEAD staining and for tagging the membranes of viable Escherichia coli and Bacillus subtilis cells. The absence of toxicity makes these dyes suitable for live-cell imaging and allows monitoring of bacterial membrane biogenesis. Moreover, a newly synthesized FR-fluorophore can be employed for imaging bacterial membranes with stimulated emission depletion microscopy, a super-resolution technique capable of increasing the resolving power of conventional microscopes
- …
