Cell-associated hydrolysis activity and cellulose-binding ability of wild-type and mutant C. themocellum strains. (A) Cell-associated hydrolysis activity. The bar graphs show the amount of reduced sugars (mg/mL) after hydrolysis of 5 mg Avicel at 55°C for 24 h under oxic conditions measured using the 3,5-dinitrosalicylic acid method . Wild-type cells incubated under the same growth conditions in the absence of Avicel were used as a control to determine the amount of reduced sugar in the absence of cellulose hydrolysis, and this amount was subtracted from the values for the experimental samples. (B) Cell adhesion to cellulose. Values for each strain were determined by calculating the percentage of cells attached to a cellulose filter paper (Watermann, 3 × 6.4 cm, 0.34 mm thickness). The values for the mutants are normalized to the percentage of C. thermocellum wild-type cells attached to the filter paper (87%), which was set equal to 1. E. coli DH5 alpha cells were used as a negative control. Average values and standard deviations indicated by error bars were calculated from three independent experiments.