Fig. 5

Normalized fluorescence and absorbance at 450 nm scale linearly during exponential phase growth of M. thaueri (A), in agreement with previously observed constant intracellular coenzyme F420 content in methanogens. The high R2 value of the regression of absorbance vs. fluorescence during exponential phase (up to 45 h) demonstrates the linearity of the normalized fluorescence:absorbance ratio (B). Dotted lines in B represent the 95 % confidence interval of the linear regression of absorbance vs. fluorescence during exponential phase