DEPARTMENT OF ORGANISMIC AND EVOLUTIONARY BIOLOGY
HARVARD UNIVERSITY

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DANIEL L. HARTL LABORATORY TEL (617) 496-3917
16 DIVINITY AVENUE November 14, 1995 | a8 (617) 496-5540
CAMBRIDGE, MASSACHUSETTS 02138 FAX (617) 496-5854

Dr Joshua Lederberg
Founder's Hall

Rockefeller University
1230 York Avenue, STE 400
New York, NY 10021-6341

Dear Josh:

We have recently finished a study of the distribution of plasmids related to F in
natural isolates of E. coli that has caused me to speculate on the origin of the F
factor in laboratory strains. The thought is summarized in the following passage
from the Discussion of the paper I am working on. I am hoping that you will
have a look at it and tell me whether you think the scenario is plausible and, if
not, why not.

"Our data also bear on the history of the F factor in laboratory strains. It has
often been remarked that LEDERBERG was extremely lucky to use a Strain in
which the F factor was derepressed owing to an insertion of IS3 in the finO gene.
However, the frequency of F-related plasmids in the ECOR strains shows that
there is a reasonable chance that any randomly selected strain might have such
a plasmid: 7 percent, of the ECOR strains have an F plasmid and 11 percent have
an R plasmid. What is remarkable in the laboratory F factor is the insertion
mutation in finO. In our PCR amplifications of the 28 finO genes in plasmids in
the ECOR collection, not one produced a product other than the expected size.
When did the insertion in the laboratory F factor take place? Probably not in
nature. We suspect that it happened in LEDERBERG'S own laboratory as various
subcultures of K-12 were isolated and examined for their ability to undergo
recombination. Any subculture with an insertion in finO would be a good at
recombination, and such a strain would certainly have been used in further
experiments. Hence, a chance insertion of IS3 interrupting finO may well have
been the result of unconscious selection -- a case of chance favoring the
prepared mind."

  
 
  

Many thanks for your consideration.
Best

 

Daniél L. Hartl v
Professor of Biology