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A. Penicillin gene clusters in Penicillium chrysogenum and Aspergillus nidulans. B. Cephalosporin gene clusters in Acremonium chrysogenum. The ‘early cluster’ contains seven genes encoding the biosynthetic steps up to penicillin N and the MFS transporters, and the ‘late cluster’ contains the two genes converting penicillin N to cephalosporin C (see text).
