krisw

Hi everyone,

    I've been at this job for 4 years and have recently started having problems with my glycerol stocks.  We freeze down 15% glycerol Ecoli stocks at -80.  The weird part is that when I go to streak that stock on a plate, the cells grow just fine.  Then, if I pick an individual colony for liquid culture, it does not grow.  This has happened recently with many different samples and so I dont believe it was just a one time mistake (for example, if I just happened to pick a bad colony).
  If I take my actual purified DNA, re-transform and then pick a colony and grow that in liquid cultrue, they grow fine.  So, I have no reason to suspect that my media or antibiotics are bad.  I am thinking that something is wrong with the actual glycerol stocks.  But what would cause the cells to grow on a plate but not in liquid culture?  Could old glycerol all of a sudden cause such problem (ours is about 6 years old)?  
   Has anyone ever had this happen?  I plan to buy a new glycerol batch and do some testing, but I want yo get your thoughts to see if I'm on the right track here.

Thanks, Kris