Extraction of plasmid-like DNA and high-quality total DNA from Porphyra yezoensis

Somatic cells were prepared from sea snail enzyme digests of Porphyra yezoensis thalli.Using SDS-Proteinase K as extraction solution,total DNA was isolated from the somatic cells.The crude extracts of total DNA were purified with glassmilk,and the resulting DNA was of sufficient quality for digestion of restriction endonuclease.DNA bands were clearly observed in the restriction patterns of EcoRI,PstI and HaeⅢ respectively.The presence of DNA bands in the restriction pattern of total DNA indicated that the genome of Porphyra yezoensis may be small.Unexpectedly,using guanidinium isothiocyanate and sarcosyl as extraction solution,a plasmid-like DNA band(2.3 Kb) was directly found in the isolated total DNA of Porphyra yezoensis.A very simple and convenient method for plasmid-like DNA isolation has been established.