Three essays on stigma

In order to complete this doctoral dissertation, I acknowledge the financial assistance from the Business Administration department at Universidad Carlos III de Madrid (PIPF UC3M 01-1920). I also gratefully acknowledge the funds provided by the CAM project 2018/00064/004 and from the Spanish FEDER/Ministerio de Ciencia e Innovación – Agencia Estatal de Investigación (Grant PID2021-123450OB-I00).Doctorado en Empresa y Finanzas. Mención InternacionalPresidente: Giacomo Fabrizio Negro.- Secretario: Luis Diestre Martín.- Vocal: Marta María Elvira Roj

Del rey filosofo al pez torpedo: metáforas sobre la enseñanza de la filosofia

ResumenDel rey filósofo al pez torpedo: metáforas sobre la enseñanza de la filosofía. La presencia de la filosofía como asignatura en la educación secundaria parece estar amenazada en algunos países. Es importante defender esa presencia, aunque eso sólo es posible si defendemos un específico modelo de enseñanza yaprendizaje de la Filosofía, que no suele ser el más compartido en la actualidad. Ahora hay un cierto predominio delmodelo basado en lametáfora platónica del Rey Filósofo, que acentúa el valor de la sabiduría filosófica y el papel del profesorado como transmisor de lamisma. Frente a estemodelo, se defiende otro basado en lamétaforadel pez torpedo, en la que se describe eldiálogo socrático como lamanera de hacer filosofía en el aula orientada a despertar y desarrollar en el alumnado la capacidadde pensar por símismo de forma crítica ycreativa.Así entendido, el aprendizaje de la filosofía debe estar presente en la educación formal desde el principio, a los tres años, hasta el final, cuando se termina la adolescencia.Palabras clave: enseñanza de la filosofía, diálogo socrático, rey filósofo.AbstractFrom the philosopher king to the torpedo fish: metaphors on the teaching of philosophy. The presence of philosophy as a discipline in secondary education seems to be endangered in some countries. It is important to defend its presence, nevertheless this is onlypossible ifwe defend a specificmodelofteaching and learning philosophy,which isnot usuallythemost popular today.There isnowa certain dominance ofthe model based on the Platonicmetaphor of the philosopher king,which emphasizesthe value of philosophicalwisdomand the role of the teacher as the personwho hands down all this tradition to students. This article defends a different model, based upon themetaphor of the torpedo fish,which describes Socratic dialogue as thewayof enacting philosophyinthe classroom, aimed at waking students'minds and fostering their abilityto think for themselves in a critical and creativeway.Thus understood, the learning of philosophyneeds to be introduced into formaleducation frombeginning: fromthe age ofthree until the end of adolescence.Keywords: philosophyteaching, Socratic dialogue, philosopher king

Release of outer membrane fragments by exponentially growing Brucella melitensis cells

Rough and smooth strains of Brucella melitensis released a membranous material that was devoid of detectable NADH oxidase and succinic dehydrogenase activity (cytoplasmic membrane markers) but that contained lipopolysaccharide, proteins, and phospholipids. This material was composed of two fractions that had similar chemical compositions but that were of different sizes which were separated by differential ultracentrifugation. Electron microscopy showed that both fractions are made of unit membrane structures. The membrane fragments were released during the exponential phase of growth, and no leakage of malic dehydrogenase activity (cytosol marker) was detected. Thus, the fragments were unlikely a result of cell lysis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis showed that, although group 2 Brucella outer membrane proteins and lipoprotein were not detected, the proteins in the membranous material were outer membrane proteins. Gas-liquid chromatography analysis showed a similar fatty acid profile for the cell envelope and the outer membrane fragments of the smooth strain B. melitensis 16M. In contrast, the outer membrane fragments from the rough 115 strain were enriched in palmitic and stearic acids. With respect to the unfractionated cell envelope, outer membrane fragments were enriched in phosphatidylcholine, a phospholipid that is unusual in bacterial membranes

Structure and properties of the outer membranes of Brucella abortus and Brucella melitensis

The brucellae are Gram-negative bacteria characteristically able to multiply facultatively within phagocytic cells and which cause a zoonosis of world-wide importance. This article reviews the structure and topology of the main components (lipopolysaccharide, native hapten polysaccharide, free lipids and proteins) of the outer membranes of Brucella abortus and B. melitensis, as well as some distinctive properties (permeability and interactions with cationic peptides) of these membranes. On these data, an outer membrane model is proposed in which, as compared to other Gram-negatives, there is a stronger hydrophobic anchorage for the lipopolysaccharide, free lipids, porin proteins and lipoproteins, and a reduced surface density of anionic groups, which could be partially or totally neutralized by ornithine lipids. This model accounts for the permeability of Brucella to hydrophobic permeants and for its resistance to the bactericidal oxygen-independent systems of phagocytes

The outer membranes of Brucella spp. are not barriers to hydrophobic permeants

The patterns of susceptibility to hydrophobic and hydrophilic drugs and the uptake of the fluorescent probe N-phenyl-naphthylamine in Brucella spp., Haemophilus influenzae, Escherichia coli, and deep rough Salmonella minnesota mutants were compared. The results show that the outer membranes of smooth and naturally rough Brucella spp. do not represent barriers to hydrophobic permeants and that this absence of a barrier relates at least in part to the properties of Brucella lipopolysaccharide

Immunological identity of brucella native hapten, polysaccharide B, and yersinia enterocolitica serotype 9 native hapten

Yersinia enterocolitica serotype 9 contained an antigenic component giving a reaction of total identity with Brucella native hapten and polysaccharide B. This component was present in a phenol-water extract (fraction 5; M. Redfearn, Ph.D. Thesis, University of Wisconsin, Madison, 1960) along with the smooth lipopolysaccharide. The native hapten could be purified free of lipopolysaccharide and proteins by gel filtration

Glucose Oxidation to Pyruvate Is Not Essential for Brucella suis Biovar 5 Virulence in the Mouse Model

Brucella species cause brucellosis, a worldwide extended zoonosis. The brucellae are related to free-living and plant-associated alpha 2-Proteobacteria and, since they multiply within host cells, their metabolism probably reflects this adaptation. To investigate this, we used the rodent-associated Brucella suis biovar 5, which in contrast to the ruminant-associated Brucella abortus and Brucella melitensis and other B. suis biovars, is fast-growing and conserves the ancestral Entner-Doudoroff pathway (EDP) present in the plant-associated relatives. We constructed mutants in Edd (glucose-6-phosphate dehydratase; first EDP step), PpdK (pyruvate phosphate dikinase; phosphoenolpyruvate pyruvate), and Pyk (pyruvate kinase; phosphoenolpyruvate -> pyruvate). In a chemically defined medium with glucose as the only C source, the Edd mutant showed reduced growth rates and the triple Edd-PpdK-Pyk mutant did not grow. Moreover, the triple mutant was also unable to grow on ribose or xylose. Therefore, B. suis biovar 5 sugar catabolism proceeds through both the Pentose Phosphate shunt and EDP, and EDP absence and exclusive use of the shunt could explain at least in part the comparatively reduced growth rates of B. melitensis and B. abortus. The triple Edd-PpdK-Pyk mutant was not attenuated in mice. Thus, although an anabolic use is likely, this suggests that hexose/pentose catabolism to pyruvate is not essential for B. suis biovar 5 multiplication within host cells, a hypothesis consistent with the lack of classical glycolysis in all Brucella species and of EDP in B. melitensis and B. abortus. These results and those of previous works suggest that within cells, the brucellae use mostly 3 and 4 C substrates fed into anaplerotic pathways and only a limited supply of 5 and 6 C sugars, thus favoring the EDP loss observed in some species

Isolation of brucella strains in cattle from sedentary and nomadic communities and its public health implication

Brucellosis is a highly infectious disease caused by bacteria of the genus brucella affecting animals leading to high economic loss and an impediment to livestock exportation. It also infects man with serious public health consequences. The disease is one of the world’smost important neglected tropical zoonoses. Brucellosis is considered endemic in Nigeria and current information on isolation in sedentary and nomadic cattle is required. We carried out an active surveillance in sedentary cattle in Kachia Grazing Reserve (KGR), Kaduna State and in nomadic communities on the Jos Plateau to isolate brucella organisms and carry out phenotypic and molecular characterization of the isolates to species leve

Molecular recognition of lipopolysaccaride by the lantibiotic nisin

Nisin is a lanthionine antimicrobial effective against diverse Gram-positive bacteria and is used as a food preservative worldwide. Its action is mediated by pyrophosphate recognition of the bacterial cell wall receptors lipid II and undecaprenyl pyrophosphate. Nisin/receptor complexes disrupt cytoplasmic membranes, inhibit cell wall synthesis and dysregulate bacterial cell division. Gram-negative bacteria are much more tolerant to antimicrobials including nisin. In contrast to Gram-positives, Gram-negative bacteria possess an outer membrane, the major constituent of which is lipopolysaccharide (LPS). This contains surface exposed phosphate and pyrophosphate groups and hence can be targeted by nisin. Here we describe the impact of LPS on membrane stability in response to nisin and the molecular interactions occurring between nisin and membrane-embedded LPS from different Gram-negative bacteria. Dye release from liposomes shows enhanced susceptibility to nisin in the presence of LPS, particularly rough LPS chemotypes that lack an O-antigen whereas LPS from microorganisms sharing similar ecological niches with antimicrobial producers provides only modest enhancement. Increased susceptibility was observed with LPS from pathogenic Klebsiella pneumoniae compared to LPS from enteropathogenic Salmonella enterica and gut commensal Escherichia coli. LPS from Brucella melitensis, an intra-cellular pathogen which is adapted to invade professional and non-professional phagocytes, appears to be refractory to nisin. Molecular complex formation between nisin and LPS was studied by solid state MAS NMR and revealed complex formation between nisin and LPS from most organisms investigated except B. melitensis. LPS/nisin complex formation was confirmed in outer membrane extracts from E. coli