Fig. 1

Improved production of TA. a Verification of the nysB disruption in the S91-ΔNB strain. The PCR products of pBY1/pBY2 and pBY3/pBY4 with S91 total DNA were 3.8 kb and 3.3 kb, respectively, and with S91- ΔNB total DNA were 2.1 kb and 1.6 kb, respectively. A 1714 bp DNA fragment in the nysB framework was deleted in the S91-ΔNB strain. b Verification of the ttmD disruption in the S91-ΔNBΔTD strain. The PCR products of pDY1/pDY2 and pDY3/pDY4 with S91-ΔNB total DNA were both 2.6 kb, and with S91-ΔNBΔTD total DNA were both 1.7 kb. An 881 bp DNA fragment in the ttmD framework was deleted in the S91-ΔNBΔTD strain. c Transcriptional analysis of the ttmRIV in the S91-ΔNBΔTD, S91-ΔNBΔTD::pSET152 and S91-ΔNBΔTD::RIV strains using qRT-PCR. The ttmRIV was under the control of the hrdB promoter. The relative values for the ttmRIV in the S91-ΔNBΔTD strain was assigned as 1, with hrdB as the internal control. d The biomass of S. ahygroscopicus S91 and its mutants. e The HPLC analysis of the fermentation products in S. ahygroscopicus S91 and its mutants. The LC-MS analysis of tetramycin A (TA), tetramycin B (TB), and nystatin A1 (NA1) are shown in Fig. S2. f Production of tetramycin A in S. ahygroscopicus S91 and its mutants. Error bars depict standard deviation of three replicates. ***P<0.001, **P<0.01, *P<0.05, and “ns”means not significant