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

<p>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 <i>in vivo</i> environments namely lung, blood and nasopharynx, M2 (B) has less of a defect. Significant change in fitness (<i>p<0</i>.<i>0125)</i> are indicated by asterisks (*). Each data point represents a single mouse.</p>