Figure 3

Mutational robustness R _μ increases with n. The horizontal axis shows the number n of reactions in a genotype and the vertical axis shows the average mutational robustness of sampled genotypes in V(n) for three environments (glucose, acetate and succinate) as a function of n. Mutational robustness R _μ is defined as the fraction of non-essential reactions in a viable genotype. It can be seen that R _μ is comparable to the acceptance rate A (cf. Figure S4 in Additional File 1). Even for n = 300, R _μ >0.15, indicating that robustness is not too low for an efficient MCMC sampling.