RESUMEN
It has been earlier hypothesized that lysogenic infection with Stx-encoding phages influences protein expression in the bacterial host, and therefore, some differentially expressed proteins could affect survival characteristics and pathogenicity. We compared the protein expression profiles of the host MG1655 and lysogens by 2D electrophoresis. Four different genes identified were all related to Fe/S subunit production, namely, nfuA, fdoH, sdhB and ftnA. To explore the role of nfuA in the biology of Stx prophage lysogeny, gene knockout experiments and phage lysogenic conversion were performed. The inactivation of nfuA caused the prophage to enter its lytic life cycle, especially under an iron-depleted condition. A similar activity was also detected in the Escherichia coli O157:H7 strain from which the Stx phage Min 27 was originally isolated. NfuA might be the positive regulator of genes controlling lysogenic cycle such as cI, cII and cIII since their transcriptional level was significantly reduced in nfuA deletion mutant as shown by qRT-PCR. We conclude that NfuA is essential for maintenance of Stx phage lysogeny in host's genetic reservoir under iron-deficient condition.
Asunto(s)
Colifagos/fisiología , Escherichia coli O157/genética , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/fisiología , Deficiencias de Hierro , Proteínas Hierro-Azufre/genética , Proteínas Hierro-Azufre/fisiología , Podoviridae/fisiología , Colifagos/química , Colifagos/genética , Electroforesis en Gel Bidimensional , Ferritinas/genética , Técnicas de Inactivación de Genes , Hierro/metabolismo , Lisogenia , Podoviridae/química , Podoviridae/genética , Profagos/genética , Proteómica , Eliminación de Secuencia , Toxina Shiga/genética , Toxina Shiga II/genéticaRESUMEN
The trag is a novel infection-related factor identified using in vivo-induced antigen technology (IVIAT) from SS2 expression libraries with swine convalescent sera. PCR-based studies of various S. suis strains collected from different sources revealed that the trag gene was present in all the virulent SS2 strains, but absent in the avirulent T15 strain. PCR and Southern hybridization analyses of a trag-knockout strain created through homologous recombination confirmed the coding sequence of trag replaced by spc (R) cassette in the ∆trag mutant. Zebrafish was used to identify the role of trag in SS2 virulence. The reduction of virulence in the trag mutant compared to the wild-type in animal model systems, laid the foundation for further studies.
Asunto(s)
Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Streptococcus suis/genética , Streptococcus suis/patogenicidad , Factores de Virulencia/genética , Factores de Virulencia/metabolismo , Animales , Southern Blotting , Modelos Animales de Enfermedad , Expresión Génica , Técnicas de Inactivación de Genes , Biblioteca de Genes , Mutagénesis Insercional , Reacción en Cadena de la Polimerasa , Infecciones Estreptocócicas/microbiología , Infecciones Estreptocócicas/patología , Infecciones Estreptocócicas/veterinaria , Streptococcus suis/aislamiento & purificación , Porcinos , Virulencia , Pez CebraRESUMEN
Adult Haemaphysalis qinghaiensis ticks from Gannan area, where ovine theileriosis is prevalent but bovine theileriosis has not been reported, transmitted Theileria parasites to yaks and sheep. Blood from the infected yak contained Theileria parasites that were infective to yaks, but not sheep. In contrast, blood from the infected sheep did not contain Theileria parasites infective to yaks. These results suggested that the ticks from the Gannan area were infected with two species of Theileria one which specifically parasitises yaks, one which parasitises sheep. Both infections were more aggressive in splenectomised hosts as compared to intact host. Adult H. qinghaiensis ticks from Zhanjiachuan area, where ovine theileriosis is prevalent but where no yaks are raised, transmitted Theileria parasites to ovine, but not yaks. Taken together these results indicate that H. qinghaiensis ticks may be infected with two different Theileria species. The species infective for sheep could be related to the newly recognised, but not yet named, pathogen recently reported in small ruminants in China. The species infective for yaks appears to be benign and is morphologically similar to parasites of the Theileria sergenti/orientalis/buffeli group.
