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Source of Founding Strain

A 1966 paper* by Seymour Lederberg (Joshua's brother) describes the derivation of the T6r, Strr, r-m-, Ara- variant of E. coli B with which we work. See section 3 of the table on page 1031 of Lederberg's paper for that derivation. The strain was then given by Seymour to Bruce Levin when they were both on the faculty at Brown University.

The first paper Bruce published using this strain was in Science (1972); it was on the ecological coexistence of two asexual strains. Bruce has told me that he did not regularly clone and freeze strains in his lab for a number of years, so some adaptation to unknown laboratory environments (LB, DM, slants, etc.) may have occurred during that time--as well as during the many years prior to that time, when microbiologists worked with the B strain.

By the time that I arrived in Bruce's lab, in April of 1982, the B strain was stored frozen. I took an aliquot to Irvine in the fall of 1985, and I re-froze a new stock from a single-colony isolate. In Irvine, I also selected the particular Ara+ variant that we now use as a spontaneous mutant on an MA plate.

Fresh single-colony isolates of the Ara- and Ara+ variants were frozen at -80C and designated as REL606 and REL607, respectively. I started the long-term experiment, which continues to this day, on February 24, 1988.

* Lederberg, S. 1966. Genetics of host-controlled restriction and modification of deoxyribonucleic acid in Escherichia coli. Journal of Bacteriology 91:1029-1036.