Two pairs of primers for two hydroxylase genes, Selleck CFTRinh-172 orf03374 (plyE) and orf14777 (plyP) were designed
and used to screen the genomic cosmid library by PCR. Genome sequencing and analysis Genome sequencing was accomplished by 454 sequencing technology. Open reading frames were analyzed using the Frame Plot 3.0 beta online [61], and the analysis of the deduced function of the proteins were Idasanutlin supplier carried out by the NCBI website [62]. Primer design, multiple nucleotide sequence alignments and analysis were performed using the BioEdit. The NRPS-PKS architecture was analyzed by NRPS-PKS online website (http://nrps.igs.umaryland.edu/nrps/) [63] and the prediction of ten amino acid of the conserved substrate-binding pocket of the A domain was performed using the online program buy BAY 63-2521 NRPS predictor (http://ab.inf.unituebingen.de/toolbox/index.php?view=domainpred) [64]. Construction of gene inactivation mutants All the mutant strains in this study were generated by homologous recombination according to the standard method [65]. The target genes were replaced with an apramycin-resistance gene from pIJ773
on SuperCos1 by traditional PCR-targeting technique. Then the recombinant plasmids were transformed into E. coli S17-1 cells for conjugation. The exconjugants would appear three days later and could be transferred to a new growth medium supplemented with apramycin (60 μg/mL) and nalidixic acid (100 μg/mL). Double-crossover mutants were identified Dichloromethane dehalogenase through diagnostic
PCR with corresponding primers (Additional file 1: Table S3). LC-MS analyses of wild type and mutant strains After finishing the fermentation, the culture broth of wild type and mutant strains were extracted by equal volume of ethyl acetate. The supernatant of the ethyl acetate phase was concentrated by rotary evaporator under the reduced pressure and finally dissolved in methanol (400 μL) for the LC-MS analysis using the Agilent 1100 series LC/MSD Trap system. The conditions for the LC-MS analysis are as follows: 55-100% B (linear gradient, 0–25 min, solvent A is water containing 0.1% formic acid, solvent B is acetonitrile containing 0.1% formic acid), 100% B (26–30 min) at the flow rate of 0.3 mL/min with a reverse-phase column ZORBAX SB-C18 (Agilent, 5 μm, 150 mm × 4.6 mm). Figure 4B was recorded with the conditions: 35-95% B (linear gradient, 0–20 min), 100% B (21–25 min), 35%B (25–40 min) at the flow rate of 0.3 mL/min. Nucleotide sequence accession number The sequence of the polyoxypeptin A biosynthetic gene cluster was deposited in GenBank with accession number KF386858. Acknowledgments This work was financially supported by the 973 programs (2010CB833805 for SL) and (2009CB118901 for ZD) from MOST, the key project (311018) from MOE and NSFC (31070057 for SL; 31121064 for ZD).