Figure 1. Shr enhances bacterial growth in the presence of free iron. Growth of WT M1T1 GAS isolate 5548, the isogenic 5448Δshr mutant, and the complemented strain 5448Δshr pShr were assessed under iron-depleted conditions (A) and in the presence of 250 μM ferric chloride (B) by measuring the turbidity of cultures at OD₆₀₀. Data points denote the arithmetic mean ± SEM and are representative of two independent experiments, each performed in duplicate. The asterisk indicates values that are statistically significantly different (p < 0.01) from WT strain 5448. (C) Quantitative real-time PCR analysis of shr and shp expression levels in stationary phase cultures of WT, 5448Δshr and 5448Δshr pShr. Data were normalized to the housekeeping gene gyrA and relative expression was compared with WT.