Successful isolation of plasmid DNA is possible from most E.coli strains, though the strain which is used can have a significant influence on the quality of the purified DNA. Host strains such as DH10b, DH5 alpha, XL10 Gold and TOP10 normally result in high quality DNA in combination with many commercially available plasmid DNA isolation kits and are therefore ideal for the propagation of plasmids to be sequenced. Lower quality DNA is derived from strains producing large amounts of carbohydrates, which are released during lysis and inhibit enzyme activity. Examples are HB101 and its derivatives such as TG1 and the JM100 series. Also strains with medium or high levels of endonuclease activity like HB101, JM101 or BL21 generate DNA of lower quality, hence a proteinase K treatment should be considered.