[Cell density mediated cellulases synthesis in Cellulosilyticum ruminicola]

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.

The study aimed to test if cell density regulation mechanism involved in the cellulase synthesis by Cellulosilyticum ruminicola H1.

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.

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.

This study demonstrates that cell density regulation is involved in cellulases synthesis by Cellulosilyticum ruminicola H1.