*2.4. Chemical Mutagenesis*

One millilitre of spore suspension of *Streptomyces albus* subsp. *chlorinus* NRRL B-24108 was inoculated into 100 mL of SG medium in a 500 mL baffled flask and cultivated overnight at 28 ◦C and 180 rpm. The pH of the culture was adjusted to 8.5 with 1 M NaOH. Ten millilitres of culture was transferred into three 50 mL falcon tubes. Then, 64 mg of wet NTG was dissolved in 16 mL of water. Next, 6.666 mL, 4.285 mL and 1.765 mL of NTG stock solution were added to the tubes containing culture to reach final NTG concentrations of 800 μg/mL, 600 μg/mL and 300 μg/mL, respectively. The samples were incubated at 28 ◦C for 30 min in the overhead shaker. The mycelium was precipitated by centrifugation, and the supernatant was discarded. The mycelium was washed twice with 5% sodium thiosulfate solution. The treated samples were plated on MS agar plates and cultivated for 14 days at 28 ◦C. The spores were washed with water and plated in dilutions on MS agar. The plates with spore dilutions were incubated for 10 days at 28 ◦C. Single colonies were picked on 30 mm plates with SG agar. The plates were incubated for 14 days at 28 ◦C. Agar blocks were cut out from the plates and transferred into 2 mL tubes. Albucidin was extracted from the agar blocks with 500 μL of butanol for 48 h. The extracts were analysed using HPLC-MS.
