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PLoS One. 2013 Dec 16;8(12):e83748. doi: 10.1371/journal.pone.0083748. eCollection 2013.

Characterization of the SigD regulon of C. difficile and its positive control of toxin production through the regulation of tcdR.

Author information

1
Laboratoire G.R.A.M. (EA 2656 IFR 23 IHURBM), Université de Rouen, Rouen, France.
2
Laboratoire Pathogenèse des Bactéries Anaérobies, Institut Pasteur, Paris, France.
3
Laboratoire Pathogenèse des Bactéries Anaérobies, Institut Pasteur, Paris, France ; Université Paris Diderot, Sorbonne Paris Cité, Cellule Pasteur, Paris, France.
4
Laboratoire G.R.A.M. (EA 2656 IFR 23 IHURBM), Université de Rouen, Rouen, France ; Laboratoire Ecosystème intestinal, Probiotiques, Antibiotiques (EA 4065, IFR IMTCE), Université Paris Descartes, Paris, France.

Abstract

Clostridium difficile intestinal disease is mediated largely by the actions of toxins A (TcdA) and B (TcdB), whose production occurs after the initial steps of colonization involving different surface or flagellar proteins. In B. subtilis, the sigma factor SigD controls flagellar synthesis, motility, and vegetative autolysins. A homolog of SigD encoding gene is present in the C.difficile 630 genome. We constructed a sigD mutant in C. difficile 630 ∆erm to analyze the regulon of SigD using a global transcriptomic approach. A total of 103 genes were differentially expressed between the wild-type and the sigD mutant, including genes involved in motility, metabolism and regulation. In addition, the sigD mutant displayed decreased expression of genes involved in flagellar biosynthesis, and also of genes encoding TcdA and TcdB as well as TcdR, the positive regulator of the toxins. Genomic analysis and RACE-PCR experiments allowed us to characterize promoter sequences of direct target genes of SigD including tcdR and to identify the SigD consensus. We then established that SigD positively regulates toxin expression via direct control of tcdR transcription. Interestingly, the overexpression of FlgM, a putative anti-SigD factor, inhibited the positive regulation of motility and toxin synthesis by SigD. Thus, SigD appears to be the first positive regulator of the toxin synthesis in C. difficile.

PMID:
24358307
PMCID:
PMC3865298
DOI:
10.1371/journal.pone.0083748
[Indexed for MEDLINE]
Free PMC Article

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