ho

THE ROCKEFELLER UNIVERSITY

pro bono humani generis
1230 YORK AVENUE - NEW YORK, NEW YORK 10021-6399

Joshua Lederberg
UNIVERSITY PROFESSOR

January 9, 1996

Dr. John J. Mekalanos

Harvard Univ

Dept Microbiol & Molec Genet,
School of Medicine

Boston, MA 02115

Dear Dr, Mekalanos:

I have wanted, for some time, to communicate to you how much excitement and admiration
you elicited on my part by your work and publications on IVET.

Your study on "Use of Genetic-Recombination as a Reporter of
Gene-Expression." struck a particular chord, as I have been interested in phase variation in
Salmonella for 40+ years. I have wondered many times whether that natural event wasn’t
hurried along by some influence of environmental stress on the existing promoters of the
recombinase.

I am sure there will be innumerable practical implications of your new discovery, beyond
what they uncover as basic science. I hope to have the chance to hear more about such
developments as they ensue.

With best wishes,

ours sin y,

oshua Lederberg