Figure 2

Illustration of the growth and sampling of cultures of (a) M600 (relA+ ppGpp+) and (b) M570 (relA- ppGpp-) on MYM TE agar. M600 progressed normally through its developmental cycle, beginning to erect aerial hyphae after 24 h and to produce the antibiotics Red after 36 h and Act after 48 h. Grey spores were also detectable from 60 h onwards. M570 failed to produce detectable amounts of pigment, and formed only a very sparse covering of aerial mycelium, first observable at 24 h. Samples 1-8 correspond to 12, 24, 36, 48, 60, 84, 96, and 120 h, respectively.