A two-component system (XydS/R) controls the expression of genes encoding CBM6-containing proteins in response to straw in Clostridium cellulolyticum

PLoS One. 2013;8(2):e56063. doi: 10.1371/journal.pone.0056063. Epub 2013 Feb 13.


The composition of the cellulosomes (multi enzymatic complexes involved in the degradation of plant cell wall polysaccharides) produced by Clostridium cellulolyticum differs according to the growth substrate. In particular, the expression of a cluster of 14 hemicellulase-encoding genes (called xyl-doc) seems to be induced by the presence of straw and not of cellulose. Genes encoding a putative two-component regulation system (XydS/R) were found upstream of xyl-doc. First evidence for the involvement of the response regulator, XydR, part of this two-component system, in the expression of xyl-doc genes was given by the analysis of the cellulosomes produced by a regulator overproducing strain when grown on cellulose. Nano-LC MS/MS analysis allowed the detection of the products of all xyl-doc genes and of the product of the gene at locus Ccel_1656 predicted to bear a carbohydrate binding domain targeting hemicellulose. RT-PCR experiments further demonstrated that the regulation occurs at the transcriptional level and that all xyl-doc genes are transcriptionally linked. mRNA quantification in a regulator knock-out strain and in its complemented derivative confirmed the involvement of the regulator in the expression of xyl-doc genes and of the gene at locus Ccel_1656 in response to straw. Electrophoretic mobility shift assays using the purified regulator further demonstrated that the regulator binds to DNA regions located upstream of the first gene of the xyl-doc gene cluster and upstream of the gene at locus Ccel_1656.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Blotting, Western
  • Carbohydrate Metabolism / genetics
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cellulase / genetics
  • Cellulase / metabolism
  • Cellulose / metabolism
  • Cellulosomes / genetics*
  • Cellulosomes / metabolism
  • Chromatography, Liquid
  • Clostridium cellulolyticum / genetics*
  • Clostridium cellulolyticum / metabolism
  • Gene Expression Regulation, Bacterial*
  • Gene Knockout Techniques
  • Glycoside Hydrolases / genetics
  • Glycoside Hydrolases / metabolism
  • Mass Spectrometry
  • Multigene Family
  • Nanotechnology
  • Polysaccharides / metabolism*
  • Protein Binding
  • Reverse Transcriptase Polymerase Chain Reaction
  • Substrate Specificity


  • Bacterial Proteins
  • Carrier Proteins
  • Polysaccharides
  • hemicellulose
  • Cellulose
  • Glycoside Hydrolases
  • hemicellulase
  • Cellulase

Grant support

This research was supported by funding from the European Community’s Seventh Framework Program FP7/2007–2013 under grant agreement no. 237942 (CLOSTNET), the Centre National de la Recherche Scientifique and Aix-Marseille Université. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.