Research Bacteriology Bldg. 54 - Room 16 VETERANSADMINISTRATION HOSPITAL HINES, ILLINOIS March 25, 1952 YOUR FILE REFERENCE: IN REPLY REFER TO: Dr. Joshua Lederberg Department of Genetics College of Agriculture University of Wisconsin Madison 6, Wisconsin Dear Dr. Lederberg: Unfortunately, in the course of a series of changes in my own fortunes since publishing the artiole about which you wrote me, I have lost both small colony variant and parent strains of E. coliwhich I used for the work I reported on in 1946, using 2-methyl 1, 4 naphthoquinone. However, through the courtesy of Dr. W. Kirohheimer of the Northwestern University Medioal School, I have been able to obtain a suboulture of one of the strains whioh I used. It was called B. ooli II in my paper, a sac&arose fermenter. I am for- warding this culture to you under separate oover. He regretted not being able to looate the E. coli I strain which I had also originally obtained from that collection. As I remember it, I subjected this strain to 6 serial streakings on plain agar, p ioking a single colony each time, and the oulture which grew from the sixth colony was the one I used with the quinone. I trust that this one strain will prove satisfactory for your purposes and that you will have no difficulty obtaining the dwarf colonies. I shall be interested to hear what suocess you have had and what conclusions you make as to whether they are in- duced or selected by the quinone. Very sinoerely, &k.&% &, -22 ~-nd+k-.~ I_ CBARLOTfE A. COLWELL, ph. D. An inquiry by or concerning an ex-service man or woman should, if possible, give veteran’s name and file number, whether C. XC, K, N, V, or H. If such file number is unknown, service or serial number should be given.