p.m.). SMM (pH 7.2) is a minimal medium comprising 0.9% glucose, 0.9%l-asparagine, 0.2% (NH4)2SO4, 0.24% Tris, 0.1% NaCl, 0.05% K2SO4, 0.02% MgSO4·7H2O, 0.01% CaCl2, 1% trace element solution (Hopwood et al., 1985), and 2.5 mM KH2PO4. YMPD see more is a nutrient-rich medium (pH 7.2) comprising 0.2% yeast extract, 0.22% meat extract, 0.4% Bacto peptone, 0.5% NaCl, 0.2% MgSO4·7H2O, and 1% glucose. Then, 25 mL of the culture was centrifuged and the cells were harvested. Cell pellets were washed twice in SMM and resuspended in 5 mL SMM medium. Two milliliters of the resulting cell suspensions were inoculated into 1 L SMM. The culture was incubated at 30 °C with reciprocal shaking (120 r.p.m.) in a
5-L baffle flask. For observation of submerged spore, cells were cultured in DM1 medium (pH 7.2) containing 25 mM MOPS, 5 mM (NH4)2SO4, 0.5 mM MgSO4·7H2O, 0.05% casamino acids (Difco), 50 mM glucose, 10 mM potassium phosphate buffer, and 0.25% trace element solution (Ensign,
1988). The following antibiotics were added as necessary: apramycin (50 μg mL−1), bialaphos (20 μg mL−1), and thiostrepton (50 μg mL−1). DNA was manipulated in Streptomyces spp. (Hopwood et al., 1985) Angiogenesis inhibitor and E. coli (Maniatis et al., 1982; Ausubel et al., 1987) as described previously. The primers used in this study are listed in Supporting Information, Table S1. Total RNA was isolated from WT cells, grown for 24 h in SMM, using an RNAqueous-Midi kit (Ambion). cDNA was then synthesized using the ThermoScript RT-PCR system (Invitrogen) and random hexamers according to the manufacturer’s instructions, and was PCR amplified using the primers listed in Table S1 (10 pmol each) under the following thermal conditions: 96 °C for 45 s, 60 °C for 1 min, and 72 °C for 30 s (30 cycles). The ΔbldKB-g mutant was constructed by deleting the entire 1614-bp bldKB-g-coding Oxymatrine sequence (except for its start and stop codons). Chromosomal DNA was used as a template in the PCR amplification described below. A 1.7-kb fragment upstream of the bldKB-g-coding sequence was amplified by PCR using
the primers bldKBUF (which contains an XbaI site) and bldKBUR (which contains a KpnI site), and then digested with XbaI and KpnI. Separately, a 1.7-kb sequence downstream of the bldKB-g-coding sequence was amplified by PCR using the primers bldKBDF (which contains a KpnI site) and bldKBDR (which contains a HindIII site), and then digested with KpnI and HindIII. The two resulting fragments were together inserted between the XbaI and the HindIII sites of pUC19. Then, an apramycin-resistance gene (aac(3)IV) was inserted into the EcoRI site of the pUC19-derived plasmid. The resulting pUC-ΔbldKB-Apr plasmid was introduced to S. griseus IFO13350 through protoplast transformation. A transformant with the plasmid integrated into its chromosome as a result of a single crossover event was selected from the apramycin-resistance colonies.