Streptomyces species produce more than 6000 antibiotics.Streptomyces coelicolor is the genetically most studied species from the in vivo through in vitro to in silico years.The 8,667,507-bp chromosome of S.coelicolor is linear.Twenty-three antibiotic biosynthetic genes or gene clsuters, including 11 polyketide (PKS) and non-ribosomal polypeptide (NRPS) biosynthetic genes, are prediceted in the genome.To obtain S.coelicolor strains with a clear background for antibiotic production, we have sequentially deleted all the PKS/NRPS gene clusters.In addition, we also deleted a 924-kb large segment near one telomere.Thus, total length of deleted sequences in S.coelicolor is 1.2 Mb, about 13.8% of the genome.When the blue-pigmented actinorhodin biosynthetic gene cluster was introduced back into these derivatives, over-production of blue pigment on plates were observed in some strains.These results indicate that minimization of S.coelicolor genome may act as a superhost for antibiotics production.