Bacteria face trade-offs in the decomposition of complex biopolymers
Fig 6
Advantages of generalists (producers of both endo and exo-enzymes).
(A, B) Comparison of the total degradation time (Tdeg) of different proportions of exo and endo-enzymes acting simultaneously. The simulation represents only the depolymerization dynamics in the absence of microbes in homogeneous conditions. The complex substrate pool was initiated with a total of 500 nmol/mm3 monomers distributed between chains of n-mers (n indicated in the figure labels). A pool with 3 nmol C/mm3 of two enzymes in different proportions act on the substrate (x-axis and color gradient with purple indicating endo-enzymes and orange indicating exo-enzymes), while the turnover rate or exo-enzyme is kexo = 0.82 h−1, the turnover of endo-enzyme is (A) kendo = kexo and (B) kendo = kexo/2. (C) Maximum biomass reached from different initial concentrations of polymers for microorganisms producing different fractions of endo and exo-enzymes. The parameters are the same as the ones used in simulation in Fig 5, except for the turnover of endo-enzymes, which is kendo = kexo/2. (D, E) Comparison of the maximum growth in the absence of diffusion max() to the maximum growth in the presence of diffusion max(Cb), for different diffusion coefficients D0 for (D) low, M = 150 nmol/mm3, and (E) high substrate, M = 1500 nmol/mm3. Each curve represents a different proportion of exo to endo-enzymes (frexo). Note that for low diffusion the ratios of maximum possible biomass would be the same, and with an increase of diffusion the growth decreases due to loss of soluble oligomers.