Ghost Plasmid !

[yeast at imtech.ernet.in]

Hi Netters :

Lately I am facing problem with my minipreps. After transforming E. coli
(BL21-^DE3) with pTrc-99A , the minipreps contained majority of DNA which was
migrating faster than the normal ccc form in the control lane. There were other
bands also which seemed to be the multimeric forms. The band  of right size was
also present but in very less amount. Restriction digestion showed that the DNA
is resistant to digestion with many enzymes. The digestion with EcoR1 resulted
in the single band of right size. This reminded       me of a discussion at
 bionet whereghost plasmids of pBluescript in XL1-Blue were discussed. Am I
 facing the similar problem. Can somebody help me ?

Thanks.

Rajesh Gupta
IMTech, Chandigarh
India