Figure 4

Activation of cellulose degradation by glucose in C. cellulolyticum. The bacterium was cultured on a mixture of 3 g/L glucose (Glu) and 3g/L cellulose (Cel), 3 g/L singular carbon source of Glu, or 3 g/L singular carbon source of Cel. The growth curves (A) and concentrations of residual cellulose (B) and glucose (D) in broth were measured. The transcriptional level of several cellulosomal genes (including those in the cel-cip cluster) was quantified using qRT-PCR (C). To test the dependence of the cellulolytic activity on glucose concentration, the bacterium was cultured on cellulose mixed with series concentrations (0.5, 1.0, 2.0, 4.0 and 8.0 g/L) of glucose; two conditions (singular cellulose and cellulose mixed with 4.0 g/L cellobiose) were used as control. The data point of 8g/L glucose was not shown. Amount of degraded cellulose was measured, and the curves of cellulose degradation were fitted by sigmoidal equation using data from three biological replicates (E). The peak cellulose degradation rate and the lag-time (the number of days it took to reach the peak rate) under each culture condition were both shown (F). Means of three biological replicates were shown.