Can bacteria that were streaked out on agar plates containing
ampicilline lose their transformed plasmid (containing AmpR) if they
have been incubated at 37 °C for several days (instead of being
incubated for 1-2 days only and then being stored at 4 °C)?
Is there any chance that bacteria which have lost the plasmid
(containing AmpR) can still grow to some degree in LB broth media
containing ampicilline?
I ask these question because in an experiment of mine I did just what
I described above and after growing up cultures from the
"over-incubated" streaks (Note: The cultures were growing unusually
slowly.), I tried to isolate plasmid DNA and the yield was extremely
low. I checked all possible errors regarding the plasmid isolation
procedure but couldn't find anything. So, I figured my bacteria might
have lost the plasmid.
I'm thankful for any comments.
Paul W.
