After incubation at 30 °C for 16–20 h, conjugation plates were overlaid with 1 mL selective

antibiotic solution with 1.25 mg mL−1 nalidixic acid and further incubated for 3–5 days until conjugants grew. Mycelia were collected after 36 and 48 h of incubation at 30 °C in 10.3% YEME medium. Total RNA was selleck screening library isolated using RNApure High-purity Total RNA Rapid Extraction kit (Bioteke) according to the manufactures’ instructions and treated with RNase-free DNase (Promega). After verifying the absence of genomic DNA contamination by PCR, cDNA was synthesized by ReverTra Ace (Toyobo). Real-time PCR was performed using the ABI 7300 Real-Time PCR Detection System and FastStart Universal SYBR Green Master Mix (Roche). Transcription of aziU3 and hrdB in wild-type S. sahachiroi Selleckchem PCI-32765 and the mutant strains were detected using two primer sets: su3for/su3rev for aziU3 and hrdBfor2/hrdBrev2 for hrdB. The relative expression levels of aziU3 normalized internally to hrdB levels were quantified by the 2−ΔΔCT method (Livak & Schmittgen, 2001) and shown as relative fold change in comparison with the 36-h samples of wild-type S. sahachiroi. All samples were run in triplicate. Wild-type S. sahachiroi and the mutant strains were cultured on GYM plates or 50 mL PS5 liquid medium in a 250-mL baffled flask at 30 °C for 3–4 days (Kelly et al.,

2008). Azinomycin B was extracted from three chopped agar plates or from 100 mL liquid culture broths with 150 mL methylene chloride in a 500-mL flask G protein-coupled receptor kinase by gently shaking at 80 r.p.m. for 2–3 h. After filtration, extracts were concentrated in vacuum and redissolved in 1 mL ether. High-performance liquid chromatography (HPLC) was performed on a Diamonsil C18 (2) column (250 × 4.6 mm), and the fractions were eluted for 10 min in 80% solvent A (H2O)/20% solvent B (CH3CN),

25 min in a linear gradient from 80% A/20% B to 20% A/80% B, followed by 2 min in a linear gradient from 20% A/80% B to 80% A/20% B, and 13 min in 80% A/20% B, at a flow rate of 0.5 mL min−1 and UV detection at 218 nm using an Waters HPLC system. Azinomycin B with a retention time of 31.4 min was confirmed by liquid chromatography–mass spectrometry (LC-MS; Shimadzu LCMS-IT-TOF) analysis, showing [M + H]+ ion at m/z = 624.2182 and [M + Na]+ ion at m/z = 646.2048 consistent with the molecular formula of azinomycin B, which is C31H33N3O11. About 200-μL cultures of wild-type S. sahachiroi and the mutant strains in 10.3% YEME medium were filtrated and added to stainless steel cylinders (Oxford cups, diameter: 8 mm) on LB agar plates that were preseeded with an overnight Bacillus subtilis 168 culture. The plates were incubated at 37 °C for 12 h, and the biological activity of azinomycin B against B. subtilis 168 was estimated by measuring the circular zone of inhibition.