outgrowth time andampicillin conc for low-copy numbe plasmid - (Mar/10/2011 )

You should grow your cells at room temperature for extremely low-copy number plasmids. Otherwise, the growth rate of your cells will be higher than the copy rate of your plasmid, and you'll have problems. I would also use Carbenicillin instead of Ampicillin, it is more stable, and will reduce your background (and thus increase your yield) immensely.

@Rsm

What kind of problems are you referring to?

No growth of bacteria, or growth of bacteria without plasmid (to avoid that you should use Carbenicilin). It would seem like they do not survive Ampicillin or maintain the plasmid.

Fortunately, no problem of such yet, even with 100ug/mL ampicillin. Plasmid yield has been reasonable with 10mL LB. So, we can simply replace ampicillin with carbenicilin for plasmids with Amp resistance?

Yes, you can just replace it, also using the same concentrations (50 or 100mg/l). It is more stable at 37C, and thus your concentration of antibiotic will be maintained for longer time.

i should try this..i'm new to plasmid work and having this problem too..