title: [Cell density mediated cellulases synthesis in Cellulosilyticum ruminicola].
abstract: Cellulosilyticum ruminicola H1 is an anaerobic cellulolytic bacterium isolated from the rumen content of yak. Previously, we found that strain H1 lost growth on filter paper cellulose after several subcultures. The growth on cellulose cannot be restored until a few transfers in the cellobiose-containing medium. This is contrary to the knowledge that microbial cellulases synthesis is induced by the substrate while repressed by the metabolites, e. g. cellobiose, but provides a hint of cell-density mediated cellulase synthesis.
  
  
  OBJECTIVE
  The study aimed to test if cell density regulation mechanism involved in the cellulase synthesis by Cellulosilyticum ruminicola H1.
  
  
  METHODS
  By using enzyme assays and real-time PCR quantification, we investigated cellulase activities and the gene transcript levels in the high- and low-cellmass cultures of strain H1. We also determined the elevation of endoglucanase and cellobiohydrolase activities and the gene expression in the low-cellmass culture upon addition of the high-cellmass spent culture.
  
  
  RESULTS
  Both endoglucanase and cellobiohydrolase of strain H1 were detected 3 to 10 times higher in the high cellmass culture than in the lower cellmass culture either in enzymatic activity or the gene transcript abundance, thus confirming the cell density-mediated cellulase synthesis.
  
  
  CONCLUSIONS
  This study demonstrates that cell density regulation is involved in cellulases synthesis by Cellulosilyticum ruminicola H1.
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Can
authors.initials: C
authors.lastname: Wang
authors.forename: Xiuzhu
authors.initials: X
authors.lastname: Dong
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D002417:Cattle; D044602:Cellulases / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D006094:Gram-Positive Bacteria / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D007700:Kinetics; D012417:Rumen / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D044602:Cellulases