Overview of mutant ‘fitness’ during dendritic cell infection. (a) A Euler diagram (Venn diagram with areas proportional to the values) showing the numbers of mutants with significant fitness costs (p < 0.05) at different times during M. tuberculosis infection of DCs (Additional file 1), (b) a plot of the ‘fitness’ rank of mutations in individual genes 3 days and 7 days after infection, Spearman’s rank-order correlation ρ = 0.856, p < 1 × 10−6. (c) a genome plot of the ‘fitness’ of intracellular M. tuberculosis mutants 7 days after infection. Red lines indicate fitness of the gene knockouts 7 days after DC infection. Black lines are genes assigned as essential in vitro  and so excluded from the analysis. Relevant regions of co-functionality are indicated around the perimeter.