To obtain small molecular antibacterial compound and its biosynthetic gene cluster,a genomic cosmid library was screened by high-throughput conjugation,heterologous expression,bioassay,and combined with DNA sequencing.A positive clone 1H5 expressing growth-inhibition activities against gram positive bacteria and Rhodotorula was obtained from the genomic library of Streptomyces hygrospinosus.The cosmid 1H5 harbored a cluster of genes highly similar to previously reported streptothricin biosynthetic gene clusters in terms of sequence and gene organization.Streptothricins were detected in the fermentation broth of Streptomyces expression hosts carrying 1H5,indicating that this clone contained an entire gene cluster for streptothricin biosynthesis.The cloning and heterologous expression of the biosynthetic gene cluster pave the way for further study of the biosynthesis,regulation and structural modification of streptothricin.