We report here the isolation and recombinational cloning of a large plasmid, pZL12, from endophytic Streptomyces sp.9R-2.pZL12 comprises 90435-bp, encoding 112 genes, 30 of which are organized in a large operon resembling bacteriophage genes.A replication locus (repA) and a conjugal transfer locus (traA-traC) were identified on pZL12.Surprisingly, the supernatant of a 9R-2 liquid culture containing partially purified phages particles could infect 9R-2 cured of pZL12 (9R-2X) to form plaques, and a phage particle (φbZL12) was observed by transmission electron microscopy.