Strains, plasmids, media, and growth conditions

The bacterial strains and plasmids used in this study as well as their relevant characteristics are listed in Table 1. The native aurachin producer Stigmatella erecta Pd e32 was grown at 30 °C on agar plates containing modified Zein medium (Sester et al. 2020). E. coli strains were routinely cultivated in standard lysogeny broth (LB) medium (Carl Roth) at 37 °C and 200 rpm, unless they possessed an auaA expression plasmid. In such a case, the respective strain was grown at 30 °C. For maintenance of plasmids, antibiotics were added to the media at the following concentrations: 100 µg mL^− 1 ampicillin, 50 µg mL^− 1 kanamycin, and chloramphenicol 30 µg mL^− 1. The growth of E. coli cultures was followed by measuring the optical density at 600 nm (OD₆₀₀).

Strains and plasmids used in this study

amp^R ampicillin resistance, kan^R kanamycin resistance, cm^R chloramphenicol resistance

For the recombinant production of aurachin D, E. coli strains were grown in 25 mL of terrific broth (TB) medium (Tartoff and Hobbs 1987), which had been supplemented with 0.04% (v/v) glycerol and 0.003% (w/v) HMQ. The production cultures were inoculated to an OD₆₀₀ of 0.1 and, subsequently, cultivated at 30 °C and 200 rpm for 24 h. If necessary, the cultures were induced with 1 mM isopropyl β-d-1-thiogalactopyranoside (IPTG) after they reached an OD₆₀₀ of 1. To induce the expression of the mevalonate biosynthesis genes from pJBEI-2997 (Peralta-Yahya et al. 2011), IPTG was added to a final concentration of 0.025 mM.