Development of a vector and host system and characterization of replication of plasmid pSQ10 in moderately halophilic Nocardiopsis.

The genus of Nocardiopsis is a new source of antibiotics, chemicals, and enzymes. Here we reported the development of a vector and host system in moderately halophilic Nocardiopsis via an oriT-mediated conjugation. By screening about 80 Nocardiopsis strains, 6 of them harbored 8 plasmids (18-80 kb). The complete nucleotide sequence of pSQ10 consisted of 18,219 bp, with 71.9% G + C content, encoding 17 open reading frames, 5 of them resembled those of Streptomyces plasmids. A rep locus (iteron within the gene) was identified for replication in Nocardiopsis sp. YIM 90083, and rep protein bound to its iteron sequence. This system may be useful for gene cloning and expression in Nocardiopsis.