No plasmid DNA from mini-prep

[KHUANG at CHEMVX.TAMU.EDU]

Hi, 
Thank your guys for your suggestion. Bacially, I should solve my problem, 
there are still something I am wondering.

Our autoclave was down recently, so the glass tube used for culturing E. coli
were sterlized 2-3 hr in 120 oC oven.  When I tried to isolate plasmid from 
overnight cultured E. coli, I could not get any plasmid DNA. Then, I reduced 
the culture time, the strange thing was that E. coli were lysised completely 
after 6 hr. So, Do you think some phage are still stick alive in glass tube(
except glass tube, other material are all autoclaved)?

Thanks again!

Huang