Fig. 1.

Corresponding substrates (1, 4) and product intermediates (2, 5) for the BorA DH M3 and FluA DH M1. The final polyketide products are illustrated on the right (3, 6). a The borrelidin PKS utilizes a trans-cyclopentane-dicarboxylate starter unit (highlighted in red) and b the fluvirucin B₁ PKS accepts an amide-containing polyketide starter unit (highlighted in blue). The dehydration reaction is highlighted in yellow. The full biosynthetic polyketide synthase pathways for borrelidin and fluvirucin B₁ are depicted in Fig. S1 (colour figure online)