(A) Growth of Δgrx3/4 in air is slow, whereas growth under argon is considerably improved. WT and Δgrx3/4 strains were grown for 16 h in YPAD with aeration and serial 1:5 dilutions of 10⁶ cells were spotted on YPAD agar plates, incubated for 3 days and photographed (upper left). Liquid cultures of WT and Δgrx3/4 strains were grown with aeration or under argon in YPAD and photographed (left panel in air, right panel under argon). (B) Hypoxia allows enhanced growth of the Δgrx3/4 double mutant. The shuffle strain (Δgrx3/4 [GRX3] No. 124-67) was grown on FOA plates for 3 days under aerobic or hypoxic conditions and photographed. (C) Growth curves of BY4741 (WT), Δgrx3/4 obtained from 124-67 lacking the covering plasmid (shuffle out) grown in air (aerobic) or under argon (hypoxic). For comparison a Δgrx3Δgrx4 strain derived from a freshly dissected tetrad (called Δgrx3/4, No. 125-28) was grown aerobically or under hypoxia.