Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of Clostidium difficile response regulator rgaR and rgbR mutants created using a reproducible method of targeted insertional inactivation of chromosomal genes

ABSTRACT: Clostridium difficile is an emerging nosocomial pathogen of increasing importance and virulence but our ability to study the molecular mechanisms underlying the pathogenesis of C. difficile-associated disease has been limited because of a lack of tools for its genetic manipulation. We have now developed a reproducible method for the targeted insertional inactivation of chromosomal C. difficile genes. The approach relies on the observation that an Escherichia coli?Clostridium perfringens shuttle vector is unstable in C. difficile and can be used as a form of conditional lethal vector to deliver gene constructs to the chromosome. We have used this methodology to insertionally inactivate two putative response regulator genes, rgaR and rgbR, which encode proteins with similarity to the toxin gene regulator, VirR, from C. perfringens. Transcriptomic analysis demonstrated that the C. difficile RgaR protein positively regulated four genes, including a putative agrBD operon. The RgaR protein was also purified and shown to bind specifically to sites that contained two consensus VirR boxes located just upstream of the putative promoters of these genes. The development of this methodology will significantly enhance our ability to use molecular approaches to develop a greater understanding of the ability of C. difficile to cause disease. Data is also available from http://bugs.sgul.ac.uk/E-BUGS-39

ORGANISM(S): Clostridium difficle

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PROVIDER: E-BUGS-39 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The virulence factors of Clostridium difficile have been studied for many years, but the main in vivo pathogenesis processes of this bacterium has to be investigated. Especially, data on the early mechanisms of C. difficile adaptation to the host is not yet available. The objective of our study was to improve the understanding of the pathogenesis of C. difficile by the analysis of the genome-wide temporal expression of C. difficile genes during the first hours of infection. Three groups of 4 axenic mice each were challenged by vegetative cells of the 630 C. difficile strain, and sacrified at 8, 14, and 38 hours post-infection. Pure prokaryotic RNA was obtained from caecal bacteria. Comparative hybridizations on strain 630 microarrays were done using cDNA issued from an 8-hours in vitro culture as control, with a dye-swap protocol for each sample. Normalisation and statistical analysis of all data were done with different functions of the limma package. The pathogenesis of C. difficile could be seen as a result of the successful metabolic adaptation of the bacteria to its host, contributing to its persistence and multiplication, and the coordinate expression of virulence factors. Analysis of our data enlightened some of these aspects. The results support strongly a two-step infection model, since there is, during the course of infection, a significant increase in the toxins expression contrasting with a decreased expression of most of the putative colonization factors. Several paralogs of the HMW S-layer protein are also down-regulated, some of them could be strong candidates as colonisation factors. Bacterial adaptation to the microenvironment of the host is assessed by the regulation of numerous metabolic pathways, i.e., the upregulation of the ethanolamine catabolic operon or the modulation of several PTS systems. Inactivation of some putative virulence factors identified by this methodology will complete this analysis. Transcriptional profiling of the C. difficile 630E strain after 8h, 14h or 38h in TY. Two-condition experiments: 630E strain 14h or 38h in TY vs. 630E strain 8h in TY. 2 biological replicates for each condition in dye swap.

Project description:The virulence factors of Clostridium difficile have been studied for many years, but the main in vivo pathogenesis processes of this bacterium has to be investigated. Especially, data on the early mechanisms of C. difficile adaptation to the host is not yet available. The objective of our study was to improve the understanding of the pathogenesis of C. difficile by the analysis of the genome-wide temporal expression of C. difficile genes during the first hours of infection. Three groups of 4 axenic mice each were challenged by vegetative cells of the 630 C. difficile strain, and sacrified at 8, 14, and 38 hours post-infection. Pure prokaryotic RNA was obtained from caecal bacteria. Comparative hybridizations on strain 630 microarrays were done using cDNA issued from an 8-hours in vitro culture as control, with a dye-swap protocol for each sample. Normalisation and statistical analysis of all data were done with different functions of the limma package. The pathogenesis of C. difficile could be seen as a result of the successful metabolic adaptation of the bacteria to its host, contributing to its persistence and multiplication, and the coordinate expression of virulence factors. Analysis of our data enlightened some of these aspects. The results support strongly a two-step infection model, since there is, during the course of infection, a significant increase in the toxins expression contrasting with a decreased expression of most of the putative colonization factors. Several paralogs of the HMW S-layer protein are also down-regulated, some of them could be strong candidates as colonisation factors. Bacterial adaptation to the microenvironment of the host is assessed by the regulation of numerous metabolic pathways, i.e., the upregulation of the ethanolamine catabolic operon or the modulation of several PTS systems. Inactivation of some putative virulence factors identified by this methodology will complete this analysis. Transcriptional profiling of the C. difficile 630E strain after 8h, 14h or 38h of infection in mouse. Three-condition experiments: 630E strain 8h, 14h or 38h of infection in mouse vs. 630E strain 8h in culture. 4 biological replicates for each condition in dye swap.

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Transcription profiling of Clostidium difficile response regulator rgaR and rgbR mutants created using a reproducible method of targeted insertional inactivation of chromosomal genes

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