e. coli cultures were 
 grown in lb liquid media 
 or on lb agar plates with antibiotics when necessary ( 50 g / ml 
 kanamycin , 50 g / ml apramycin , 25 to 50 g / ml chloramphenicol , 
 50 g / ml carbenicillin ) at 37 c with shaking . streptomyces liquid precultures were grown in tryptic soy 
 broth with the appropriate antibiotics ( 50 g / ml kanamycin , 
 50 g / ml apramycin , 25 g / ml nalidixic acid ) , inoculated 
 into ssm media ( 1% soytone , 1% soluble starch , 2% maltose , 0.5% trace 
 element solution , ph 5.7 ) and grown at 30 c with shaking . streptomyces were also grown on mannitol soya flour medium 
 plates ( 2.0% agar , 2.0% mannitol , 2.0% soya flour ) with appropriate 
 antibiotics ( 50 g / ml kanamycin , 50 g / ml apramycin , 25 
 g / ml nalidixic acid ) . salinispora were grown 
 in a1 media ( 1.0% starch , 0.4% yeast extract , 0.2% peptone , and 2.8% 
 sea salt ) at 30 c with shaking . the method 
 of tar capturing used in this study 
 has been previously reported . the isolation 
 of high - quality genomic dna from salinispora was 
 performed according to standard procedures . the capture vector , pcap01 , containing yeast arsh4/cen6 and trp1 
 marker , e. coli puc ori , streptomyces c31 integrase gene(int ) , its attachment site ( attp ) and origin 
 of dna transfer ( orit ) , aph(3)ii gene ( kan / neo resistance ) , 
 and two 1 kb regions flanking the gene cluster on either side was 
 used to capture and propagate the enterocin gene cluster . the vector 
 pcap01 with the captured enc gene cluster from s. pacifica cnt-150 was named pbb01 . the plasmid pbb01 and its derivatives 
 were conjugated into s. lividans tk23 and s. coelicolor m1146 
 using a standard triparental mating method with e. coli et 12567/pbb01 and e. coli et 12567/pub307 . after 6 days of growth in ssm media , the cultures 
 were extracted with four volumes of etoac and concentrated in vacuo . the extracts were then dissolved in 100 l 
 of mecn and analyzed by hplc using a luna 5u c18 column 
 ( 150 mm  4.60 mm , 5 m beads ) with a linear gradient of 
 2100% mecn in water with 0.1% tfa over 30 min with a flow rate of 0.7 
 ml / min . hplc - hr - esi - msms 
 analysis of all extracts was carried out on an agilent 1290 q - tof 
 ( 2002000 m / z , 20 kev ) . the 
 data were subjected to the molecular networking workflow and analyzed 
 as described previously . the inactivation of the acyl - coa 
 synthetase encoding gene , enc16 , in the heterologous 
 host strain s. coelicolor m1146-pbb01 was done using 
 -red recombination with an apramycin - resistant marker ( aac(3)iv ) 
 as described previously .
heterologous expression of secondary 
 metabolic pathways is a promising 
 approach for the discovery and characterization of bioactive natural 
 products . 
 herein we report the first heterologous expression of a 
 natural product from the model marine actinomycete genus salinispora . using the recently developed method of yeast - mediated transformation - associated 
 recombination for natural product gene clusters 
 , we captured a type 
 ii polyketide synthase pathway from salinispora pacifica with high homology to the enterocin pathway from streptomyces 
 maritimus and successfully produced enterocin in two different streptomyces host strains . 
 this result paves the way for 
 the systematic interrogation of salinispora s 
 promising secondary metabolome .