Colony morphology upon plating on Congo Red agar plates. Well-grown broth cultures of all strains were diluted 1:106 and 100 μl plated in triplicate onto Middlebrook agar with OADC containing 100 μg ml-1 Congo Red. Plates were incubated on average for three weeks. The arrows point to smooth-domed-opaque (sdo), smooth-flat-red (sfr), smooth transparent (st), rough red (rr) and rough transparent (rt) colonies. A: WT; B: mutant MAV_2555; C: mutant MAV_1888; D: mutant MAV_4334; E: mutant MAV_5106; F: mutant MAV_1778; G: mutant MAV_3128; H: mutant MAV_3625; I: mutant MAV_2599.