E.coli OP50

I wonder if someone could tell me what the O, P and 50 stand for in E.coli OP50? Thanks.

Hi, an interesting question that probably Sydney Brenner could answer most easily. However, just out of interest I looked at the history of the OP50 strain.

It seems to be a derivative of the E coli BB strain according to one reference, of the E coli B strain according to another.

The former seems more likely as in the late 50’s, Gunther Stent’s group had a number of uracil auxotrophs derived from E coli BB (Berkeley) for uracil incorporation studies …Gunther Stent knew and collaborated with Sydney Brenner and perhaps Brenner noted in his earlier work that uracil auxotrophs grew slowly and used this to his advantage later with C elegans?..

Why OP50, just a guess, perhaps the OP are initials of a lab worker or colleague/collaborator of Gunther Stent and the 50 refers to the 50th derivative tested for uracil auxotrophy in Stent’s lab? However, Margery Hoogs was working with stent at the time…so not sure who the mystery OP is if a person at all…

Hope that adds to the excitment and someone clears this up (Sydney perhaps??)


despite the warning in red that this is an old topic, I thought it was important to add one last bit of information regarding the ancestory of OP50.

So Sydney Brenner did clear this one up (ok I admit it, not by replying to me directly). In a Worm Breeder’s Gazette article from December 2009 on the genome sequencing of OP50;


Sydney Brenner added a note “OP50 is a mutant of E. coli B (Berkeley strain). The Berkeley strain grew rI and rII mutants of T4 as r+.

Those interested in the ancestry of E. coli B and BB and all the clan can read this article,


It’s a fascinating journey through time tracing a path from Bordet, Bronfenbrenner, Delbrück, Hershey, Luria, Stent & Ledeberg and the blossoming of the field of Bacteriophage genetics (and hence molecular biology).

Happy Sunday…