RESUMEN
Streptococci are a diverse group of Gram-positive microorganisms sharing common virulence traits and similar strategies to escape the oral niche and establish an infection in other parts of the host organism. Invasive infection with oral streptococci is "a perfect storm" that requires the concerted action of multiple biotic and abiotic factors. Our understanding of streptococcal pathogenicity and infectivity should probably be less mechanistic and driven not only by the identification of novel virulence factors. The observed diversity of the genus, including the range of virulence and pathogenicity mechanisms, is most likely the result of interspecies interactions, a massive horizontal gene transfer between streptococci within a shared oral niche, recombination events, selection of specialized clones, and modification of regulatory circuits. Selective pressure by the host and bacterial communities is a driving force for the selection of virulence traits and shaping the streptococcal genome. Global regulatory events driving niche adaptation and interactions with bacterial communities and the host steer research interests towards attempts to define the oral interactome on the transcriptional level and define signal cross-feeding and co-expression and co-regulation of virulence genes.
Asunto(s)
Boca/microbiología , Streptococcus/genética , Streptococcus/patogenicidad , Factores de Virulencia/genética , Adaptación Psicológica , Metabolismo de los Hidratos de Carbono , Regulación Bacteriana de la Expresión Génica , Transferencia de Gen Horizontal , Genes Bacterianos , Genoma Bacteriano , Humanos , Microbiota , Enfermedades de la Boca/microbiología , Infecciones Estreptocócicas/microbiología , Streptococcus/metabolismo , Streptococcus anginosus/genética , Streptococcus anginosus/patogenicidad , Streptococcus mitis/genética , Streptococcus mitis/patogenicidad , Streptococcus pyogenes/genética , Streptococcus pyogenes/patogenicidad , Virulencia/genéticaRESUMEN
Poland's first Enterobacteriaceae isolate producing the New Delhi metallo-ß-lactamase (NDM) was identified in August 2011. Escherichia coli sequence type ST410 NDM-1 was cultured from a critically ill patient who had been transferred directly from the Congo. The blaNDM-1 gene was carried by conjugative IncFII-type plasmid pMC-NDM (87,619 bp), which showed structural similarity to plasmid pGUE-NDM, which was identified earlier in France in an E. coli ST131 isolate of Indian origin.
Asunto(s)
Infecciones por Escherichia coli/microbiología , Escherichia coli/genética , Plásmidos/química , beta-Lactamasas/genética , Antibacterianos/uso terapéutico , Farmacorresistencia Bacteriana Múltiple , Escherichia coli/aislamiento & purificación , Infecciones por Escherichia coli/tratamiento farmacológico , Infecciones por Escherichia coli/patología , Resultado Fatal , Expresión Génica , Humanos , Masculino , Persona de Mediana Edad , Tipificación de Secuencias Multilocus , PoloniaRESUMEN
We have cloned and analysed the arcA gene which encodes a transcriptional activator necessary for the high-level expression of two genes for enzymes of the arginine catabolic pathway in Aspergillus nidulans: agaA (for arginase) and otaA (for ornithine transaminase, OTAse). Here we present complete genomic and cDNA sequences for, and describe the pattern of expression of, the arcA gene. This gene contains one intron and encodes a polypeptide of 600 amino acids. The deduced protein belongs to the family of Zn(2)Cys(6) fungal regulatory proteins. ARCA is the first known protein of this family that has glycine instead of the conserved proline at the fifth position in the second, six-residue, loop of the Zn cluster domain. We have established that transcription of the arcA gene is not self-regulated and does not depend on arginine. Two mutations in arcA, one gain-of-function and one loss-of-function, have been sequenced and the effects of these mutations on the expression of the agaA gene at the transcriptional level are reported.
Asunto(s)
Arginina/metabolismo , Aspergillus nidulans/genética , Proteínas Fúngicas/genética , Genes Fúngicos , Genes Reguladores , Transactivadores/genética , Secuencia de Aminoácidos , Arginasa/biosíntesis , Arginasa/genética , Secuencia de Bases , Clonación Molecular , Datos de Secuencia Molecular , Mutación , Ornitina-Oxo-Ácido Transaminasa/biosíntesis , Ornitina-Oxo-Ácido Transaminasa/genética , Regiones Promotoras Genéticas , Análisis de Secuencia de ADN , Homología de Secuencia de Ácido Nucleico , Transcripción Genética , Dedos de ZincRESUMEN
Transcription initiation of the copy-number control and better-than-random segregation genes of the broad-host-range and low-copy-number plasmid pSM19035 are subjected to repression by the autoregulated pSM19035-encoded omega product in Bacillus subtilis cells. The promoters of the copS (Pcop1 and Pcop2), delta (Pdelta), and omega (Pomega) genes have been mapped. These promoters are embedded in a set of either seven copies of a 7-bp direct repeat or in a block consisting of two 7-bp direct repeats and one 7-bp inverted repeat; the blocks are present either two or three times. The cooperative binding of omega protein to the repeats on the Pcop1, Pcop2, Pdelta, and Pomega promoters represses transcription initiation by a mechanism that does not exclude sigma(A)RNAP from the promoters. These results indicate that omega protein regulates plasmid maintenance by controlling the copy number on the one hand and by regulating the amount of proteins required for better-than-random segregation on the other hand.