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  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 07 January 2014, Vol.111(1), pp.355-60
    Description: Antibiotic-resistant isolates of Salmonella enterica were selected on plates containing lethal concentrations of rifampicin, kanamycin, and nalidixic acid. The stability of the resistance phenotype was scored after nonselective growth. Rifampicin-resistant (Rif(r)) isolates were stable, suggesting that they had arisen by mutation. Mutations in the rpoB gene were detected indeed in Rif(r) mutants. In contrast, a fraction of kanamycin-resistant (Km(r)) and nalidixic acid-resistant (Nal(r)) isolates showed reduced resistance after nonselective growth, suggesting that mechanisms other than mutation had contributed to bacterial survival upon lethal selection. Single-cell analysis revealed heterogeneity in expression of the porin gene ompC, and subpopulation separation provided evidence that reduced ompC expression confers adaptive resistance to kanamycin. In the case of Nal(r) isolates, mutations in the gyrA gene were present in most nalidixic acid-resistant isolates. However, the efflux pump inhibitor Phe-Arg-β-naphtylamide (PAβN) reduced the level of resistance in Nal(r) mutants, indicating that active efflux contributes to the overall level of nalidixic acid resistance. Heterogeneous efflux pump activity was detected in single cells and colonies, and a correlation between high efflux and increased resistance to nalidixic acid was found. These observations suggest that fluctuations in the expression and the activity of critical functions of the bacterial cell, alone or combined with mutations, can contribute to adaptive resistance to antibiotics.
    Keywords: Anti-Bacterial Agents -- Pharmacology ; Drug Resistance, Bacterial -- Genetics ; Kanamycin -- Pharmacology ; Nalidixic Acid -- Pharmacology ; Rifampin -- Pharmacology ; Salmonella Enterica -- Genetics
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 2
    Language: English
    In: PLoS ONE, 2012, Vol.7(3), p.e32823
    Description: Cell polarization is key for the function of most eukaryotic cells, and regulates cell shape, migration and tissue architecture. Fission yeast, Schizosaccharomyces pombe cells are cylindrical and polarize cell growth to one or both cell tips dependent on the cell cycle stage. Whereas microtubule cytoskeleton contributes to the positioning of the growth sites by delivering polarity factors to the cell ends, the Cdc42 GTPase polarizes secretion via actin-dependent delivery and tethering of secretory vesicles to plasma membrane. How growth is restricted to cell tips and how re-initiation of tip growth is regulated in the cell cycle remains poorly understood. In this work we investigated the function of protein phosphatase type 2A (PP2A) in S. pombe morphogenesis by deleting the evolutionary conserved PTPA-type regulatory subunit that we named pta2 . pta2 -deleted cells showed morphological defects and altered growth pattern. Consistent with this, actin patches and active Cdc42 were mislocalized in the pta2 deletion. These defects were additive to the lack of Cdc42-GAP Rga4. pta2 Δ cells show upregulated Cdc42 activity and pta2 interacts genetically with polarisome components Tea1, Tea4 and For3 leading to complete loss of cell polarity and rounded morphology. Thus, regulation of polarity by PP2A requires the polarisome and involves Pta2-dependent control of Cdc42 activity.
    Keywords: Research Article ; Biology ; Genetics And Genomics ; Microbiology ; Biochemistry
    E-ISSN: 1932-6203
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  • 3
    Language: English
    In: The Biochemical journal, 01 January 2012, Vol.441(1), pp.481-5
    Description: In the present paper, we report that transcription affects the location of a DNA target in Escherichia coli K-12. A strain whose chromosome had been engineered to encode a lac repressor-GFP (green fluorescent protein) fusion was used as a host for a low copy number plasmid that carries an array of five lac operator sites. Individual cells of this strain exhibited a diffuse fluorescence signal, suggesting that the plasmid is distributed throughout the cell cytoplasm. However, a derivative of this plasmid carrying a cloned constitutive promoter is targeted to a location at the edge of the nucleoid towards the pole of the host cell. We conclude that transcription from the cloned promoter is driving the location of the plasmid and that specific locations in bacterial cells may favour gene expression.
    Keywords: Escherichia Coli K12 -- Metabolism ; Escherichia Coli Proteins -- Metabolism ; Gene Expression Regulation, Bacterial -- Physiology ; Promoter Regions, Genetic -- Genetics
    ISSN: 02646021
    E-ISSN: 1470-8728
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  • 4
    Language: English
    In: Microbiology (Reading, England), August 2011, Vol.157(Pt 8), pp.2220-5
    Description: Ribonucleoside diphosphate reductase (RNR) is located in discrete foci in a number that increases with the overlapping of replication cycles in Escherichia coli. Comparison of the numbers of RNR, DnaX and SeqA protein foci with the number of replication forks at different growth rates reveals that fork : focus ratios augment with increasing growth rates, suggesting a higher cohesion of the three protein foci with increasing number of forks per cell. Quantification of NrdB and SeqA proteins per cell showed: (i) a higher amount of RNR per focus at faster growth rates, which sustains the higher cohesion of RNR foci with higher numbers of forks per cell; and (ii) an equivalent amount of RNR per replication fork, independent of the number of the latter.
    Keywords: Cell Division ; DNA Replication ; Chromosomes -- Metabolism ; Escherichia Coli -- Growth & Development ; Ribonucleoside Diphosphate Reductase -- Metabolism
    ISSN: 13500872
    E-ISSN: 1465-2080
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  • 5
    Language: English
    In: Current Opinion in Microbiology, 2015, Vol.25, p.9(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.mib.2015.03.004 Byline: Maria A Sanchez-Romero, Ignacio Cota, Josep Casadesus Abstract: * Bacterial genomes contain C.sup.5-methyl-cytosine, N.sup.4-methyl-cytosine, and N.sup.6-methyl-adenine. * Base methylation controls DNA-protein interactions. * DNA methylation plays roles in bacterial virulence. * Methylome analysis may open a new era in bacterial epigenomics. Author Affiliation: Departamento de Genetica, Universidad de Sevilla, Apartado 1095, 41080 Seville, Spain
    Keywords: Genetic Research – Analysis ; Purines – Analysis ; Bacterial Genetics – Analysis ; Methylation – Analysis ; Bacteria – Analysis ; Virulence (Microbiology) – Analysis ; DNA – Analysis
    ISSN: 1369-5274
    Source: Cengage Learning, Inc.
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  • 6
    Language: English
    In: Current Opinion in Microbiology, June 2015, Vol.25, pp.9-16
    Description: Formation of C -methyl-cytosine, N -methyl-cytosine, and N -methyl-adenine in bacterial genomes is postreplicative, and occurs at specific targets. Base methylation can modulate the interaction of DNA-binding proteins with their cognate sites, and controls chromosome replication, correction of DNA mismatches, cell cycle-coupled transcription, and formation of epigenetic lineages by phase variation. During four decades, the roles of DNA methylation in bacterial physiology have been investigated by analyzing the contribution of individual methyl groups or small methyl group clusters to the control of DNA–protein interactions. Nowadays, single-molecule real-time sequencing can analyze the DNA methylation of the entire genome (the ‘methylome’). Bacterial methylomes provide a wealth of information on the methylation marks present in bacterial genomes, and may open a new era in bacterial epigenomics.
    Keywords: Biology
    ISSN: 1369-5274
    E-ISSN: 1879-0364
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  • 7
    Language: English
    In: Scientific Reports, 01 October 2018, Vol.8(1), pp.1-11
    Description: Abstract Salmonella enterica pathogenicity island 1 (SPI-1) is a gene cluster that encodes a type III secretion system and effectors involved in epithelial cell invasion. SPI-1 undergoes bistable expression, with concomitant formation of SPI-1 ON and SPI-1 OFF lineages. This study describes single cell analysis of SP1-1 bistability and epithelial cell invasion, and reports the unsuspected observation that optimal invasion of epithelial cells requires the presence of both SPI-1 ON and SPI-1 OFF subpopulations. The contribution of SPI-1 OFF cells to optimal invasion may rely on their ability to invade epithelial cells if a SPI-1 ON subpopulation is present. In fact, Salmonella SPI-1 mutants are also able to invade epithelial cells in the presence of SPI-1 ON Salmonellae, a phenomenon described in the 1990’s by Galán and co-workers. Invasion by SPI-1 OFF cells does not seem to involve a diffusible factor. A small number of SPI-1 ON cells is sufficient to endow the bacterial population with invasion capacity, a feature that may permit host colonization regardless of the bottlenecks encountered by Salmonella populations inside animals.
    Keywords: Biology
    E-ISSN: 2045-2322
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  • 8
    Language: English
    In: 2015, Vol.11(11), p.e1005667
    Description: The Salmonella enterica opvAB operon is a horizontally-acquired locus that undergoes phase variation under Dam methylation control. The OpvA and OpvB proteins form intertwining ribbons in the inner membrane. Synthesis of OpvA and OpvB alters lipopolysaccharide O-antigen chain length and confers resistance to bacteriophages 9NA (Siphoviridae), Det7 (Myoviridae), and P22 (Podoviridae). These phages use the O-antigen as receptor. Because opvAB undergoes phase variation, S . enterica cultures contain subpopulations of opvAB OFF and opvAB ON cells. In the presence of a bacteriophage that uses the O-antigen as receptor, the opvAB OFF subpopulation is killed and the opvAB ON subpopulation is selected. Acquisition of phage resistance by phase variation of O-antigen chain length requires a payoff: opvAB expression reduces Salmonella virulence. However, phase variation permits resuscitation of the opvAB OFF subpopulation as soon as phage challenge ceases. Phenotypic heterogeneity generated by opvAB phase variation thus preadapts Salmonella to survive phage challenge with a fitness cost that is transient only. ; A tradeoff can increase the adaptive capacity of an organism at the expense of lowering the fitness conferred by specific traits. This study describes a tradeoff that confers bacteriophage resistance in Salmonella enterica at the expense of reducing its pathogenic capacity. Phase variation of the opvAB operon creates two subpopulations of bacterial cells, each with a distinct lipopolysaccharide structure. One subpopulation is large and virulent but sensitive to phages that use the lipopolysaccharide O-antigen as receptor, while the other is small and avirulent but phage resistant. In the presence of a phage that targets the O-antigen, only the avirulent subpopulation survives. However, phase variation permits resuscitation of the virulent opvAB OFF subpopulation as soon as phage challenge ceases. This transient tradeoff may illustrate the adaptive value of epigenetic mechanisms that generate bacterial subpopulations in a reversible manner.
    Keywords: Research Article
    ISSN: 1553-7390
    E-ISSN: 1553-7404
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  • 9
    Language: Spanish
    In: Revista internacional administración finanzas : RIAF, 2010, Vol.3(1), pp. 49-59
    ISSN: 1933608X
    Source: Deutsche Zentralbibliothek für Wirtschaftswissenschaften
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  • 10
    Language: Spanish
    In: Enfermedades Infecciosas y Microbiologia Clinica, 2010, Vol.28, pp.16-24
    Description: El programa de formación de los residentes en microbiología y parasitología recoge su proyección clínica, desde la orientación diagnóstica del paciente y obtención de muestras adecuadas para el diagnóstico de las enfermedades infecciosas, hasta las medidas de tratamiento y control de infección. Asimismo, aborda los nuevos retos de la microbiología clínica y asegura su participación en programas de control de las infecciones asociadas a instituciones de cuidados de salud, la resolución de problemas en salud pública y la aplicación de los nuevos métodos de microbiología molecular. La docencia de la especialidad se realiza a licenciados en medicina, farmacia, biología, bioquímica y química mediante el sistema de residencia (4 años) en 61 unidades docentes acreditadas, presentes en casi todas las comunidades autónomas (CC.AA.). En los últimos años, se han producido desequilibrios importantes entre la oferta de plazas (0,17 por 100.000 habitantes) y los especialistas que terminan su residencia (0,13 por 100.000 habitantes), con una distribución poco homogénea por CC.AA. La tendencia actual en Europa refuerza la figura del microbiólogo clínico como eje central en el área del diagnóstico de las enfermedades infecciosas y su función en el terreno de la microbiología de salud pública. La derivación de pruebas microbiológicas a laboratorios externalizados polivalentes, con escasa participación de especialistas en microbiología y proyectos no sedimentados de troncalidad dificulta la aplicación de los programas de formación. La cercanía a la clínica, en colaboración con otros especialistas, son actitudes inherentes e irrenunciables en la formación de los especialistas en microbiología y parasitología. The training program of residents in microbiology and parasitology in Spain includes clinical skills, ranging from the diagnostic approach to the patient and adequate sample collection for diagnosis of infectious diseases to antimicrobial therapy and infection control measures. Training also includes new challenges in clinical microbiology that ensure residents’ participation in infection control programs of health-care associated infections, training in the resolution of public health problems, and application of new molecular microbiology methods. Specialization in clinical microbiology may be undertaken by graduates in Medicine, Biology, Biochemistry and Chemistry. The training is performed in accredited microbiology laboratories at different hospitals (n = 61) across the country through 4-year residency programs. In the last few years, there has been a major imbalance between the number of intended residents (0.17 per 100,000 inhabitants) and those graduating as specialists in clinical microbiology (0.13 per 100,000 inhabitants), with wide variations across the country. The current tendency in Europe is to strengthen the role of clinical microbiologists as key figures in the diagnosis of infectious diseases and in public health microbiology. Training programs have been hampered by the practice of sending samples for microbiological tests to external, centralized multipurpose laboratories with few clinical microbiologists and without a core curriculum. Essential elements in the training of specialists in clinical microbiology are a close relationship between the laboratory and the clinical center and collaboration with other specialists.
    Keywords: Microbiología Y Parasitología ; Microbiología Clínica ; Programa de Formación ; Troncalidad ; Microbiology and Parasitology ; Clinical Microbiology ; Training Program ; Core Curriculum ; Medicine
    ISSN: 0213-005X
    E-ISSN: 15781852
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