Fitness-based epistatic analysis. (a) Correlation between measured and estimated single mutant growth rates. (b) Histograms of fitness-based epistasis scores (F-Score) calculated for all TF-TF pairs (grey) and those associated with high confidence genetic interactions (red) in the presence of MMS. Insert displays the corresponding histograms in the absence of MMS. (c) The number of epistatic interactions identified for each TF, categorized according to the environment where the interaction was identified. 18 interactions are identified exclusively in absence of MMS, 15 are identified only in the presence of MMS and 12 are identified in both environments.