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

Sobre el origen del SARS-CoV-2

The current COVID-19 pandemic is arguably dividing the population between those who believe that SARS-CoV-2 has a natural origin and those who are convinced that it is a man-made virus that escaped from the laboratory. This article provides evidence for its likely natural origin. Only the Chinese government’s lack of transparency prevents the conspiracy and denialist hypotheses from being dismissed.Se puede decir que la pandemia de COVID-19 que estamos sufriendo divide a la población entre los que piensan que el SARS-CoV-2 tiene un origen natural y los que están convencidos de que es un virus artificial que se escapó del laboratorio. En este artículo se dan las pruebas que apuntan a que, con toda probabilidad, el origen del virus es natural. Solo la falta de trasparencia del gobierno chino impide descartar las hipótesis conspiranoicas y negacionistas

Identification of new IS711 insertion sites in Brucella abortus field isolates

<p>Abstract</p> <p>Background</p> <p>Brucellosis is a zoonosis caused by <it>Brucella </it>spp., a group of highly homogeneous bacteria. The insertion sequence IS<it>711 </it>is characteristic of these bacteria, and occurs in variable numbers and positions, but always constant within a given species. This species-associated polymorphism is used in molecular typing and identification. Field isolates of <it>B. abortus</it>, the most common species infecting cattle, typically carry seven IS<it>711 </it>copies (one truncated). Thus far, IS<it>711 </it>transposition has only been shown <it>in vitro </it>and only for <it>B. ovis </it>and <it>B. pinnipedialis</it>, two species carrying a high number of IS<it>711 </it>copies, but never in other <it>Brucella </it>species, neither <it>in vitro </it>nor in field strains.</p> <p>Results</p> <p>We found several <it>B. abortus </it>strains isolated from milk and aborted fetuses that carried additional IS<it>711 </it>copies in two hitherto undescribed insertion sites: one in an intergenic region near to the 3' end of a putative lactate permease gene and the other interrupting the sequence of a <it>marR </it>transcriptional regulator gene. Interestingly, the second type of insertion was identified in isolates obtained repeatedly from the same herd after successive brucellosis outbreaks, an observation that proves the stability and virulence of the new genotype under natural conditions. Sequence analyses revealed that the new copies probably resulted from the transposition of a single IS<it>711 </it>copy common to all <it>Brucella </it>species sequenced so far.</p> <p>Conclusions</p> <p>Our results show that the replicative transposition of IS<it>711 </it>can occur under field conditions. Therefore, it represents an active mechanism for the emergence of genetic diversity in <it>B. abortus </it>thus contributing to intra-species genetic polymorphism.</p

Disinformation in times of pandemic: typology of hoaxes on Covid-19

Drawing upon the misinformation stories debunked by the three accredited fact-checking platforms in Spain, a content analysis of all the hoaxes (N = 292) bound to the Covid-19 pandemic is performed, over the first month of the state of alarm decreed by the Spanish Government (March 14th, 2020 – April 13th, 2020). The study shows that the hoaxes about the coronavirus were disseminated mainly on social networks and, among them, especially in closed ones, such as the WhatsApp mobile messaging application. It also detects the most frequent formal and content peculiarities of misinformation. The results reveal that the pandemic, in addition to generating a large number of hoaxes on health and science, also led to the dissemination of many political fake news. The formats, sources and territories of origin of the hoaxes are also explored. Beyond the empirical results, this study makes theoretical contributions in the framework of the emerging studies on information disorders. Specifically, it provides a definition of hoax, as well as a typology in which four main types are identified: joke, exaggeration, decontextualization and deception. Based on these four types, a ‘hoax severity diagram’ is proposed

Desinformación en tiempos de pandemia: tipología de los bulos sobre la Covid-19 // Disinformation in times of pandemic: typology of hoaxes on Covid-19

Drawing upon the misinformation stories debunked by the three accredited fact-checking platforms in Spain, a content analysis of all the hoaxes (N = 292) bound to the Covid-19 pandemic is performed, over the first month of the state of alarm decreed by the Spanish Government (March 14th, 2020 – April 13th, 2020). The study shows that the hoaxes about the coronavirus were disseminated mainly on social networks and, among them, especially in closed ones, such as the WhatsApp mobile messaging application. It also detects the most frequent formal and content peculiarities of misinformation. The results reveal that the pandemic, in addition to generating a large number of hoaxes on health and science, also led to the dissemination of many political fake news. The formats, sources and territories of origin of the hoaxes are also explored. Beyond the empirical results, this study makes theoretical contributions in the framework of the emerging studies on information disorders. Specifically, it provides a definition of hoax, as well as a typology in which four main types are identified: joke, exaggeration, decontextualization and deception. Based on these four types, a ‘hoax severity diagram’ is proposed

Desinformación en tiempos de pandemia: tipología de los bulos sobre la Covid-19 // Disinformation in times of pandemic: typology of hoaxes on Covid-19

Drawing upon the misinformation stories debunked by the three accredited fact-checking platforms in Spain, a content analysis of all the hoaxes (N = 292) bound to the Covid-19 pandemic is performed, over the first month of the state of alarm decreed by the Spanish Government (March 14th, 2020 – April 13th, 2020). The study shows that the hoaxes about the coronavirus were disseminated mainly on social networks and, among them, especially in closed ones, such as the WhatsApp mobile messaging application. It also detects the most frequent formal and content peculiarities of misinformation. The results reveal that the pandemic, in addition to generating a large number of hoaxes on health and science, also led to the dissemination of many political fake news. The formats, sources and territories of origin of the hoaxes are also explored. Beyond the empirical results, this study makes theoretical contributions in the framework of the emerging studies on information disorders. Specifically, it provides a definition of hoax, as well as a typology in which four main types are identified: joke, exaggeration, decontextualization and deception. Based on these four types, a ‘hoax severity diagram’ is proposed

Transcriptome Analysis of the Brucella abortus BvrR/BvrS Two-Component Regulatory System

International audienceBackgroundThe two-component BvrR/BvrS system is essential for Brucella abortus virulence. It was shown previously that its dysfunction alters the expression of some major outer membrane proteins and the pattern of lipid A acylation. To determine the genes regulated by BvrR/BvrS, we performed a whole-genome microarray analysis using B. abortus RNA obtained from wild type and bvrR mutant cells grown in the same conditions.Methodology/Principal FindingsA total of 127 differentially expressed genes were found: 83 were over expressed and 44 were less expressed in the bvrR mutant. Two operons, the phosphotransferase system and the maltose transport system, were down-regulated. Several genes involved in cell envelope or outer membrane biogenesis were differentially expressed: genes for outer membrane proteins (omp25a, omp25d), lipoproteins, LPS and fatty acid biosynthesis, stress response proteins, chaperones, flagellar genes, and twelve genes encoding ABC transport systems. Ten genes related with carbon metabolism (pckA and fumB among others) were up-regulated in the bvrR mutant, and denitrification genes (nirK, norC and nosZ) were also regulated. Notably, seven transcriptional regulators were affected, including VjbR, ExoR and OmpR that were less expressed in the bvrR mutant. Finally, the expression of eleven genes which have been previously related with Brucella virulence was also altered.Conclusions/SignificanceAll these data corroborate the impact of BvrR/BvrS on cell envelope modulation, confirm that this system controls the carbon and nitrogen metabolism, and suggest a cross-talk among some regulators to adjust the Brucella physiology to the shift expected to occur during the transit from the extracellular to the intracellular niche

Deletion of the GI-2 integrase and the wbkA flanking transposase improves the stability of Brucella melitensis Rev 1 vaccine

Brucella melitensis Rev 1 is the best vaccine available for the prophylaxis of small ruminant brucellosis and, indirectly, for reducing human brucellosis. However, Rev 1 shows anomalously high rates of spontaneous dissociation from smooth (S) to rough (R) bacteria, the latter being inefficacious as vaccines. This S-R instability results from the loss of the O-polysaccharide. To overcome this problem, we investigated whether some recently described mechanisms promoting mutations in O-polysaccharide genes were involved in Rev 1 S-R dissociation. We found that a proportion of Rev 1 R mutants result from genome rearrangements affecting the wbo O-polysaccharide loci of genomic island GI-2 and the wbkA O-polysaccharide glycosyltransferase gene of the wbk region. Accordingly, we mutated the GI-2 int gene and the wbk IS transposase involved in those arrangements, and found that these Rev 1 mutants maintained the S phenotype and showed lower dissociation levels. Combining these two mutations resulted in a strain (Rev 2) displaying a 95% decrease in dissociation with respect to parental Rev 1 under conditions promoting dissociation. Rev 2 did not differ from Rev 1 in the characteristics used in Rev 1 typing (growth rate, colonial size, reactivity with O-polysaccharide antibodies, phage, dye and antibiotic susceptibility). Moreover, Rev 2 and Rev 1 showed similar attenuation and afforded similar protection in the mouse model of brucellosis vaccines. We conclude that mutations targeting genes and DNA sequences involved in spontaneous O-polysaccharide loss enhance the stability of a critical vaccine phenotype and complement the empirical stabilization precautions taken during S Brucella vaccine production.This work was funded by MINECO (reference project AGL2011-30453-C04) of Spain, the FIMA foundation and the European Union’s FP7/2007-2013 (grant agreement n° 221948, ICONZ - Integrated control of Neglected Zoonoses) and CSIC JAE-Doc program (FSE)

Desinformación en tiempos de pandemia: tipología de los bulos sobre la Covid-19

Se presenta un análisis de contenido de todos los bulos (N=292) relacionados con la pandemia Covid-19 identificados por las tres plataformas de verificación acreditadas en España, durante el primer mes del estado de alarma decretado por el Gobierno (14 marzo 2020 – 13 abril 2020). El estudio muestra que los bulos sobre el coronavirus fueron diseminados principalmente en las redes sociales y, entre ellas, sobre todo en las cerradas, como la aplicación móvil de mensajería WhatsApp. También detecta las particularidades formales y de contenido más frecuentes de los contenidos falsificados. Los resultados revelan que la pandemia, además de generar un gran número de bulos sobre salud y ciencia, casi un tercio de la muestra, también propició la difusión de numerosos contenidos falsos de tema político y gubernamental. El artículo explora los formatos, fuentes y territorios de procedencia de los bulos. Más allá de sus resultados empíricos, este estudio realiza contribuciones teóricas en el marco de los emergentes estudios sobre desórdenes informativos. En concreto, aporta una definición propia de bulo, así como una tipología en la que se identifican cuatro tipos de bulos: broma, exageración, descontextualización y engaño. A partir de esos cuatro tipos, se propone un ‘diagrama de gravedad de los bulos’