Clandol y Florencia sirvieron de testigos. Dn. Joseph le bautiza y Selin queda christiano. LX, p.59 [Material gráfico]

Resumen: Descripción: escena donde Selin es bautizado en el interior de una habitación enpresencia de dos testigos

La Traca : semanari pa la gent de tro: Año III Número 59 - 7 febrero 1886

Recurso electrónico. Valencia: BVNP, 2014

CTXφ immunity: Application in the development of cholera vaccines

CTXφ is a filamentous bacteriophage that encodes cholera toxin, the principal virulence factor of Vibrio cholerae. CTXφ is unusual among filamentous phages because it encodes a repressor and forms lysogens. CTXφ can infect the existing live-attenuated V. cholerae vaccine strains derived from either the El Tor or classical V. cholerae biotypes and result in vaccine reversion to toxinogenicity. Intraintestinal CTXφ transduction assays were used to demonstrate that El Tor biotype strains of V. cholerae are immune to infection with the El Tor-derived CTXφ, whereas classical strains are not. The El Tor CTXφ repressor, RstR, was sufficient to render classical strains immune to infection with the El Tor CTXφ. The DNA sequences of the classical and El Tor CTXφ repressors and their presumed cognate operators are highly diverged, whereas the sequences that surround this “immunity” region are nearly identical. Transcriptional fusion studies revealed that the El Tor RstR mediated repression of an El Tor rstA-lacZ fusion but did not repress a classical rstA-lacZ fusion. Likewise, the classical RstR only repressed a classical rstA-lacZ fusion. Thus, similar to the mechanistic basis for heteroimmunity among lambdoid phages, the specificity of CTXφ immunity is based on the divergence of the sequences of repressors and their operators. Expression of the El Tor rstR in either El Tor or classical live-attenuated V. cholerae vaccine strains effectively protected these vaccines from CTXφ infection. Introduction of rstR into V. cholerae vaccine strains should enhance their biosafety.

CTXφ contains a hybrid genome derived from tandemly integrated elements

CTXφ is a filamentous, temperate bacteriophage whose genome includes ctxAB, the genes that encode cholera toxin. In toxigenic isolates of Vibrio cholerae, tandem arrays of prophage DNA, usually interspersed with the related genetic element RS1, are integrated site-specifically within the chromosome. We have discovered that these arrays routinely yield hybrid virions, composed of DNA from two adjacent prophages or from a prophage and a downstream RS1. Coding sequences are always derived from the 5′ prophage whereas most of an intergenic sequence, intergenic region 1, is always derived from the 3′ element. The presence of tandem elements is required for production of virions: V. cholerae strains that contain a solitary prophage rarely yield CTX virions, and the few virions detected result from imprecise excision of prophage DNA. Thus, generation of the replicative form of CTXφ, pCTX, a step that precedes production of virions, does not depend on reversal of the process for site-specific integration of CTXφ DNA into the V. cholerae chromosome. Production of pCTX also does not depend on RecA-mediated homologous recombination between adjacent prophages. We hypothesize that the CTXφ-specific proteins required for replication of pCTX can also function on a chromosomal substrate, and that, unlike the processes used by other integrating phages, production of pCTX and CTXφ does not require excision of the prophage from the chromosome. Use of this replication strategy maximizes vertical transmission of prophage DNA while still enabling dissemination of CTXφ to new hosts.