Fig. 1

The effects of iron on S. pogona and Western blot verification of bfr recombinant strains. a Effects of different Fe concentrations (0, 20, 100 μM and 5 mM) on strain growth. b Effects of different Fe concentrations (0, 20, 100 μM and 5 mM) on the production of butenyl-spinosyn. The detection wavelength was set to 250 nm, and the chromatographic peak of butenyl-spinosyn appeared at approximately 13 min. c Effects of different Fe concentrations (0, 20, 100 μM and 5 mM) on the gene transcriptional levels of polyketide synthase genes. S. pogona was cultured in SFM containing different concentrations of Fe at 30 °C for 4 d, and total RNA was extracted separately and analyzed by qRT-PCR. 16S rRNA served as the normalization control. d Western blot verification of bfr recombinant strains. RNAP-β was used as an internal protein control. The averages from three biological replicates are shown. Error bars represent the standard deviation of the mean. *, ** and *** indicate P < 0.05, P < 0.01 and P < 0.005, respectively, compared to the wild-type under the same conditions