Detection of plasmids in actinomycetes that produce oxytetracycline and neomycin

: Crude preparations of DNA isolated from Act. rimosus 907, an oxytetracycline-producing organism and Act. fradiae 676, a neomycin-producing organism were analyzed with electrophoresis in agarose gel followed by electron microscopic analysis of DNA isolated from the gel. It was found that Act. rimosus and Act. fradiae contained ring molecules of DNA with the molecular masses of 37 . 10(6) and 59 . 10(6) dalton respectively.