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op-50 genotype

Leon Avery leon at eatworms.swmed.edu
Thu Sep 12 09:23:16 EST 2002

>Does anyone know the genotype of OP-50?

I once wrote to Brenner to ask this question.  I then lost his 
response (brilliant!), but I think I remember the gist: it is a 
uracil auxotroph of a non-K12 E coli strain (E coli B, I think).  So, 
it is not a genetically well-characterized strain.  As Brenner's 1974 
paper explains, a uracil auxotroph was chosen because prototrophs 
tend to produce inconveniently thick lawns.  I also remember from 
conversation in the Horvitz Lab some 15 years ago that OP50 is a bit 
leaky -- the idea was that it would be able to grow slowly in the 
absence of uracil, rather than being completely blocked.  OP50 tends 
to produce snakes, a known characteristic of E coli unable to make 
thymine (because growth continues while replication is blocked), and 
spontaneous faster-growing colonies that I isolated from NGM plates 
did not have this characteristic.  However, they also failed to grow 
on minimal medium, to my surprise.

Leon Avery                                        (214) 648-4931 (voice)
Department of Molecular Biology                            -1488 (fax)
University of Texas Southwestern Medical Center
6000 Harry Hines Blvd                            leon at eatworms.swmed.edu
Dallas, TX  75390-9148                  http://eatworms.swmed.edu/~leon/


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