By Harold McGee
Molds are microbes that require oxygen to grow, can tolerate drier conditions than bacteria, and produce powerful protein- and fat-digesting enzymes that improve the texture and flavor of certain cheeses. Molds readily develop on the rind of almost any cheese that is not regularly wiped to prevent it. The French St.-Nectaire develops a surface as variegated as lichen-covered rocks in the fields, with spots of bright yellow or orange standing out from a complex, muted background. Some cheeses are gardened to allow a diverse flora to develop, while others are seeded with one particular desired mold. The standard garden variety molds come from the large and various genus Penicillium, which also gave us the antibiotic penicillin.