Overview of fungal vs. bacterial type I PKSs. Type I PKSs can be divided into three types, non-reducing (nr), partially-reducing (pr) and highly-reducing (hr). Fungal type I PKSs generally follow an iterative logic using a single AT, KS, and T iteratively, whereas bacterial type I PKS use modules of PKS machinery sequentially. PksA, polyketide synthase A from aflatoxin biosynthesis; 6-MSAS, 6-methyl salicylic acid cynthase; TENS, tenellin synthase; DEBS, 6-deoxyerythronolide B synthase.