Genetic interaction mapping in combination with gene-expression analysis reveals temporally constrained regulation of the pyrimidine pathway. (A) A schematic of the pyrimidine pathway that produces UMP from L-glutamine by utilizing eight genes that mediate seven enzymatic reactions. (B) Tn-seq fitness for all eight genes from the pyrimidine pathway and 1 × 1 fitness to confirm the phenotypes for genes SP0702 and SP1276. Also, 1 × 1 fitness in the lung and nasopharynx is shown for SP1276 and the observed Tn-seq fitness for all double mutants between SP2193 and the eight genes from the pyrimidine pathway. (C) Quantitative reverse transcription–polymerase chain reaction experiments were done for the first seven of the genes in the de novo pyrimidine biosynthetic pathway, the response regulator SP2193, and the cognate sensor kinase SP2192. A strong induction is observed after 90 min of exposure to glucose for all seven genes in a wild-type background, while the induction is absent in a Δ2193 background.
