RESUMEN
Prokaryotes have developed multiple strategies to survive phage attack and invasive DNA. Recently, a novel genetic program denominated the CRISPR/Cas system was demonstrated to have a role in these biological processes providing genetic immunity. This defense mechanism is widespread in the Archaea and Bacteria, suggesting an ancient origin. In the last few years, progress has been made regarding the functionality of the CRISPR/Cas system; however, many basic aspects of the system remain unknown. For instance, there are few studies about the conditions and regulators involved in its transcriptional control. In this work, we analyzed the transcriptional organization of the CRISPR/Cas system as well as the positive and negative regulators involved in its genetic expression in Salmonella enterica serovar Typhi. The results obtained show that in S. Typhi the CRISPR/Cas system is a LeuO-dependent operon silenced by the global regulator LRP, in addition to the previously known nucleoid-associated protein H-NS; both LRP and H-NS bind upstream and downstream of the transcriptional start site of casA. In this study, relevant nucleotides of the casA regulatory region that mediate its LeuO transcriptional activation were identified. Interestingly, specific growth conditions (N-minimal medium) were found for the LeuO-independent expression of the CRISPR/Cas system in S. Typhi. Thus, our work provides evidence that there are multiple modulators involved in the genetic expression of this immune system in S. Typhi IMSS-1.
Asunto(s)
Proteínas Bacterianas/metabolismo , Proteínas de Unión al ADN/metabolismo , Regulación Bacteriana de la Expresión Génica , Proteína Reguladora de Respuesta a la Leucina/metabolismo , Operón , Salmonella typhi/genética , Factores de Transcripción/metabolismo , Análisis Mutacional de ADN , ADN Bacteriano/química , ADN Bacteriano/genética , ADN Bacteriano/metabolismo , Ensayo de Cambio de Movilidad Electroforética , Datos de Secuencia Molecular , Regiones Promotoras Genéticas , Unión Proteica , Análisis de Secuencia de ADN , Eliminación de SecuenciaRESUMEN
Salmonella enterica serovar Typhi (S. Typhi) is the aetiological agent of typhoid fever in humans. This bacterium is also able to persist in its host, causing a chronic disease by colonizing the spleen, liver and gallbladder, in the last of which the pathogen forms biofilms in order to survive the bile. Several genetic components, including the yihU-yshA genes, have been suggested to be involved in the survival of Salmonella in the gallbladder. In this work we describe how the yihU-yshA gene cluster forms a transcriptional unit regulated positively by the cAMP receptor global regulator CRP (cAMP receptor protein). The results obtained show that two CRP-binding sites on the regulatory region of the yihU-yshA operon are required to promote transcriptional activation. In this work we also demonstrate that the yihU-yshA transcriptional unit is carbon catabolite-repressed in Salmonella, indicating that it forms part of the CRP regulon in enteric bacteria.
Asunto(s)
Proteínas de la Membrana Bacteriana Externa/metabolismo , Proteína Receptora de AMP Cíclico/metabolismo , Regulación Bacteriana de la Expresión Génica , Hidroxibutirato Deshidrogenasa/metabolismo , Operón , Salmonella typhi/genética , Salmonella typhi/metabolismo , Proteínas de la Membrana Bacteriana Externa/genética , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Sitios de Unión , Represión Catabólica , Humanos , Hidroxibutirato Deshidrogenasa/química , Hidroxibutirato Deshidrogenasa/genética , Mutagénesis Sitio-Dirigida , Salmonella typhi/crecimiento & desarrollo , Fiebre Tifoidea/microbiologíaRESUMEN
OmpW of Salmonella enterica serovar Typhimurium has been described as a minor porin involved in osmoregulation, and is also affected by environmental conditions. Biochemical and genetic evidence from our laboratory indicates that OmpW is involved in efflux of and resistance towards paraquat (PQ), and its expression has been shown to be activated in response to oxidative stress. In this study we have explored ompW expression in response to PQ. Primer extension and transcriptional fusions showed that its expression was induced in the presence of PQ. In silico analyses suggested a putative binding site for the SoxS transcriptional factor at the ompW regulatory region. Electrophoretic mobility shift assays (EMSAs) and footprinting experiments showed that SoxS binds at a region that starts close to -54 and ends at about -197 upstream of the transcription start site. Transcriptional fusions support the relevance of this region in ompW activation. The SoxS site is in the forward orientation and its location suggests that the ompW gene has a class I SoxS-dependent promoter.
Asunto(s)
Proteínas de la Membrana Bacteriana Externa , Proteínas Bacterianas/metabolismo , Regulación Bacteriana de la Expresión Génica/efectos de los fármacos , Salmonella typhimurium/metabolismo , Transactivadores/metabolismo , Proteínas de la Membrana Bacteriana Externa/biosíntesis , Proteínas de la Membrana Bacteriana Externa/genética , ADN Bacteriano/análisis , ADN Bacteriano/genética , Electroforesis en Gel de Poliacrilamida , Ensayo de Cambio de Movilidad Electroforética , Herbicidas/farmacología , Paraquat/farmacología , Regiones Promotoras Genéticas , Salmonella typhimurium/efectos de los fármacos , Salmonella typhimurium/genética , Análisis de Secuencia de ADN , Activación Transcripcional/efectos de los fármacosRESUMEN
The relevance toward virulence of a variety of two-component signal transduction systems is reviewed for 16 pathogenic bacteria, together with the wide array of environmental signals or conditions that have been implicated in their regulation. A series of issues is raised, concerning the need to understand the environmental cues that determine their regulation in the infected host and in the environment outside the laboratory, which shall contribute toward the bridging of bacterial pathogenesis and microbial ecology.
Asunto(s)
Bacterias/patogenicidad , Fenómenos Fisiológicos Bacterianos , Transducción de Señal , Animales , Bacterias/genética , Infecciones Bacterianas/microbiología , Ecosistema , Humanos , VirulenciaRESUMEN
Expression of bfpA, the gene coding for the structural subunit of the bundle-forming pili (BFP) in enteropathogenic Escherichia coli (EPEC), requires the product of bfpT (also called perA), a member of the AraC family of transcriptional regulators. Here, we show that bfpT-cat fusions were not expressed in a bfpT - or in a non-EPEC strain, unless a functional bfpT was present, indicating that an autoregulatory mechanism is involved in expression. Further experiments with bfpT-cat fusions and primer extension analysis showed that bfpT is transcribed from a conventional sigma-70 promoter and that it is expressed throughout the growth curve. It is regulated in response to the ammonium concentration, temperature and growth media, in the same proportions as those described previously for bfpA. In addition, bfpT and bfpA expression was also modulated by osmolarity, but was not affected by pH, iron excess or limitation. Deletion analysis of the bfpT upstream region revealed that a DNA segment of 81 bp, extending upstream from the transcriptional start site, contained all the sequence elements required for maximal expression of bfpT. Furthermore, it shares significant homology with a bfpA upstream AT-rich region, which has been shown to be involved in the BfpT-dependent regulation of bfpA. Interestingly, ammonium repression was observed only when bfpT-cat or bfpA-cat expression was complemented in an EPEC background, whereas low-temperature regulation was observed in both EPEC and non-EPEC strains. This suggests that specific regulatory elements are present in EPEC, while others are shared with non-pathogenic E. coli.
Asunto(s)
Proteínas Bacterianas , Medios de Cultivo/farmacología , Proteínas de Escherichia coli , Escherichia coli/genética , Proteínas Fimbrias , Regulación Bacteriana de la Expresión Génica , Compuestos de Amonio Cuaternario/farmacología , Proteínas Represoras/genética , Factores de Transcripción , Transcripción Genética/genética , Secuencia de Aminoácidos , Factor de Transcripción de AraC , Proteínas de la Membrana Bacteriana Externa/biosíntesis , Proteínas de la Membrana Bacteriana Externa/genética , Secuencia de Bases , ARN Polimerasas Dirigidas por ADN/metabolismo , Escherichia coli/patogenicidad , Regulación Bacteriana de la Expresión Génica/efectos de los fármacos , Genes Bacterianos , Genes Reporteros , Concentración de Iones de Hidrógeno , Hierro/farmacología , Datos de Secuencia Molecular , Familia de Multigenes , Concentración Osmolar , Regiones Promotoras Genéticas/genética , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Represoras/biosíntesis , Proteínas Represoras/fisiología , Eliminación de Secuencia , Homología de Secuencia de Ácido Nucleico , Factor sigma/metabolismo , Temperatura , Virulencia/genéticaRESUMEN
The Salmonella typhi ompS1 gene codes for an outer membrane protein of the OmpC/OmpF porin family. It is expressed at very low levels, relative to the major porins. However, deletion analysis of the 5' regulatory region showed that the gradual removal of nucleotides -310 to -88, upstream from the P1 major transcriptional start-point, resulted in a stepwise increase in expression, reaching levels 10-fold above those for the ompC major porin gene. Hence, this 222 bp segment contains cis-acting regulatory elements involved in negative control. Primer extension analysis revealed the presence of three promoters: P1 activity was OmpR dependent; P2 was expressed at a lower level in the absence of OmpR; and P3 had a minor constitutive activity. OmpR bound preferentially to box II, an 18 bp F1/C1 canonical site, the removal (-88 to -66) of which resulted in a decrease in expression thus supporting its role in positive control. Expression of ompS1 was not induced by a set of stress conditions, including a shift in osmolarity, nor was the IHF regulator involved in negative control. An ompS1 homologue was found in E. coli K-12, which contains a nonsense codon and a shift in the reading frame, whereas Salmonella typhimurium contains an open reading frame in this region. Thus, S. typhi ompS1 provides novel features in OmpR regulation.
Asunto(s)
Proteínas de la Membrana Bacteriana Externa/genética , Proteínas de la Membrana Bacteriana Externa/metabolismo , Proteínas Bacterianas , Regulación Bacteriana de la Expresión Génica , Salmonella typhi/crecimiento & desarrollo , Salmonella typhi/genética , Transactivadores/metabolismo , Secuencia de Bases , Huella de ADN , Electroforesis en Gel de Poliacrilamida , Eliminación de Gen , Genes Bacterianos , Genes Reporteros , Datos de Secuencia Molecular , Porinas , Regiones Promotoras Genéticas , Salmonella typhi/metabolismo , Análisis de Secuencia de ADN , Transactivadores/genética , Transcripción Genética , Equilibrio HidroelectrolíticoRESUMEN
In theoretical descriptions formulated during the 1600s, R. Descartes attributed a clock-like role to the pineal gland. He established the belief that pineal function underlies the laws of the universe that determine the cyclic sleep-awake states in man. Recent reports about pineal circadian pacemakers now validate the brilliant accuracy of Cartesian thought, in relation to the relevant role of the pineal gland.
Asunto(s)
Relojes Biológicos/fisiología , Metáfora , Glándula Pineal/fisiología , Animales , Ritmo Circadiano/fisiología , HumanosRESUMEN
bfpA expression in enteropathogenic Escherichia coli is regulated by growth medium, temperature, and ammonium concentration and requires the BfpT protein (also called PerA), a member of the AraC family of transcriptional activators. Site-directed and PCR random mutagenesis, as well as deletion analysis of the bfpA upstream regulatory region, supported assignment of the promoter elements and demonstrated that the cis-acting elements that mediate BfpT-dependent regulation of bfpA are located between positions -85 and -46. Interestingly, this region shares 73% identity with a 40-bp-long AT-rich tract located upstream of the bfpT gene, which is essential for bfpT autoregulation.
Asunto(s)
Proteínas de la Membrana Bacteriana Externa/genética , Proteínas de Escherichia coli , Escherichia coli/genética , Proteínas Fimbrias , Regulación Bacteriana de la Expresión Génica/genética , Secuencias Reguladoras de Ácidos Nucleicos/genética , Escherichia coli/patogenicidad , Mutación , Regiones Promotoras Genéticas/genética , ARN Bacteriano/análisis , ARN Mensajero/análisis , Proteínas Recombinantes de Fusión , Alineación de Secuencia , Eliminación de Secuencia , Homología de Secuencia de Ácido Nucleico , Transactivadores/genéticaRESUMEN
Escherichia coli, an important indicator of the presence of fecal material, was isolated from indoor and outdoor environments in Mexico City. The heterogeneity of E. coli was represented by 89 serotypes, most of them coming from settled-dust indoor samples; 21% of them presented antibiotic multiresistance. The numbers of plasmids were higher among the antibiotic-resistant strains. The results of this study suggest that intestinal infections produced by environmental strains could be of more epidemiological impact than previously thought.
Asunto(s)
Microbiología del Aire , Microbiología Ambiental , Escherichia coli/aislamiento & purificación , Contaminación del Aire Interior , Diarrea/epidemiología , Diarrea/microbiología , Farmacorresistencia Microbiana , Polvo , Escherichia coli/clasificación , Escherichia coli/efectos de los fármacos , Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/microbiología , Escherichia coli O157/aislamiento & purificación , Heces/microbiología , Vivienda , Humanos , México/epidemiología , Serotipificación , Salud UrbanaAsunto(s)
Infecciones Bacterianas/prevención & control , Infecciones Bacterianas/economía , Infecciones Bacterianas/epidemiología , Infecciones Bacterianas/genética , Congresos como Asunto , Objetivos , Humanos , México/epidemiología , Apoyo a la Investigación como Asunto/organización & administraciónRESUMEN
The hypoglycemic activity of a purified extract from prickly pear cactus (Opuntia fuliginosa) was evaluated on STZ-induced diabetic rats. Blood glucose and glycated hemoglobin levels were reduced to normal values by a combined treatment of insulin and Opuntia extract. When insulin was withdrawn from the combined treatment, the prickly pear extract alone maintained normoglycemic state in the diabetic rats. The blood glucose response to administered glucose also showed that the rats receiving the combination treatment of insulin and Opuntia extract for 7 weeks followed by Opuntia extract alone were capable of rapidly returning blood glucose to the levels of the nondiabetic rats. Although the mechanism of action is unknown, the magnitude of the glucose control by the small amount of Opuntia extract required (1 mg/kg body weight per day) preclude a predominant role for dietary fiber. These very encouraging results for diabetes control by the purified extract of this Opuntia cactus make the need for clinical studies in humans evident.
Asunto(s)
Diabetes Mellitus Experimental/tratamiento farmacológico , Hipoglucemiantes/uso terapéutico , Plantas Medicinales , Animales , Glucemia/análisis , Hemoglobina Glucada/análisis , Masculino , Extractos Vegetales/uso terapéutico , Ratas , Ratas Wistar , EstreptozocinaRESUMEN
Se presenta el caso de un lactante de 7 meses de edad con insuficiencia renal aguda, quien presentó un cuadro de hidrotórax en la cavidad pleural izquierda al ser sometido a diálisis peritoneal. Esta complicación ocurre por paso del líquido de diálisis a la cavidad torácica, ya sea a través de los vasos linfáticos o de defectos diafragmáticos. El tratamiento conservador mediante posición de Fowler fue exitoso
Asunto(s)
Lactante , Humanos , Femenino , Peritonitis/etiología , Pleura/fisiopatología , Lesión Renal Aguda/diagnóstico , Lesión Renal Aguda/terapia , Diálisis Peritoneal/efectos adversos , Hidrotórax/diagnóstico , Radiografía Torácica/métodosRESUMEN
Rhizobium leguminosarum biovar phaseoli CFN23 loses its ability to nodulate beans at a high frequency because of a deletion of part of its symbiotic (pSym) plasmid (Soberón-Chávez et al., 1986). We report here that at least 80 kb of pSym are deleted upon loss of the symbiotic phenotype; the deletion removes the nitrogenase structural nifHDK and the common nodABC genes. The size of the deleted pSym is not reduced, since it is accompanied by an amplification of other pSym plasmid sequences. This genetic rearrangement is similar to the deletion and amplification of yeast mitochondrial DNA leading to 'petite' mutations.
Asunto(s)
ADN Bacteriano/biosíntesis , Plásmidos/genética , Rhizobium/genética , Simbiosis/genética , Southern Blotting , Deleción Cromosómica , Fabaceae/microbiología , Amplificación de Genes , Genes Bacterianos , Fijación del Nitrógeno/genética , Nitrogenasa/genética , Fenotipo , Plantas MedicinalesAsunto(s)
Fibrosis Quística/genética , ADN/análisis , Adolescente , Adulto , Niño , Preescolar , Fibrosis Quística/metabolismo , Familia , Femenino , Tamización de Portadores Genéticos , Humanos , Masculino , México , Biología Molecular , LinajeRESUMEN
The complete coding sequence of the nitrogenase reductase gene (nifH) is present in three different regions of a Rhizobium phaseoli symbiotic plasmid. Homology between two of the regions containing nifH coding sequences extends over 5 kilobases. These in turn share 1.3 kilobases of homology with the third region. The nucleotide sequences of the three nitrogenase reductase genes were found to be identical. Site-directed insertion mutagenesis indicated that none of the three genes is indispensable for nitrogen fixation during symbiosis with Phaseolus vulgaris. This implies that at least two of the reiterated genes can be functionally expressed.