Regulation by the pyrR RNA element is crucial for in vivo survival and virulence of S. pneumoniae.

1x1 competition assays (mutant vs wild type T4) reveals fitness defects of pyrR RNA mutants in a mouse infection model. While M1 (A) and M3 (C) display severe defects in all the tested in vivo environments namely lung, blood and nasopharynx, M2 (B) has less of a defect. Significant change in fitness (p<0.0125) are indicated by asterisks (*). Each data point represents a single mouse.