Genetic interaction network of five query genes. Interactions between two genes (i and j) are depicted as a line (edge) between two genes (nodes) and were determined by Tn-seq and supplemented with interactions from the STRING database (confidence >0.5; only edges were added and no nodes). Genetic interactions are divided into seven categories depicted underneath the network. Wi, fitness of mutant in gene i; Wj, fitness of mutant in gene j; Wij, fitness of double mutant. In the top section, genes i and j confer different fitness; in the bottom section, genes i and j have an equal fitness effect. This scheme results in seven color coded genetic interaction categories: synergistic (Wi=Wj<Wij), partial masking (Wi<Wj<Wij), masking (Wi<Wj=Wij), partial suppression (Wi<Wij<Wj), suppression (Wi=Wij<Wj), antagonistic (Wij<Wi≤Wj) and co-equal (Wi=Wj=Wij) (see Methods for further details). Arrows depict the hypothesized direction of the interaction. Nodes are color coded according to their involvement in a biological process or molecular function. Numbers in nodes refer to Streptococcus pneumoniae TIGR4 gene numbers (SP_number).