Skip to main contentU.S. National Library of MedicineU.S. National Library of Medicine

Profiles in Science
Pinterest badge Follow Profiles in Science on Pinterest!

The Joshua Lederberg Papers

Letter from John Loutit to Joshua Lederberg pdf (175,272 Bytes) transcript of pdf
Letter from John Loutit to Joshua Lederberg
Item is handwritten.
Number of Image Pages:
2 (175,272 Bytes)
1951-10 (October 1951)
Loutit, John
Lederberg, Joshua
The National Library of Medicine's Profiles in Science program has made every effort to secure proper permissions for posting items on the web site. In this instance, however, it has either not been possible to identify or contact the current copyright owner. If you have information regarding the copyright owner, please contact us at
Lederberg Grouping: Correspondence B
Box Number: 7
Folder Number: 170
Unique Identifier:
Accession Number:
Document Type:
Letters (correspondence)
Physical Condition:
Series: Correspondence, 1935-2002
SubSeries: 1947-1953
Folder: Loutit, John
Bacteriology Dept
University of Adelaide
South Australia
Dear Dr Lederberg,
I have delayed so long to write to you that you have probably forgotten our original correspondence. If you remember I was unable to obtain any mutant cultures from strain of Pseudomonas pyocyanen following xray treatment and obtained some helpful suggestions from you.
I might mention at the start that I had tried an incubation period (after irradiation) in complete medium before looking for mutants without any success.
The penicillin technique was one which was unfamiliar and on trial has proved very successful. I have had to use pencillin at 10,000 units/ml in the technique, a value which is considerably higher than the 1000 units/ml which you quoted you had used with Px. fluorescence. Probably the only reason for continuing with the organism has been pure stubbornness. The work was originally started as a means of investigating the high resistance of the Pseudomonas to most of the common chemotherapeutic agents. It was felt that there might well be changes in resistance to some of the agents associated with changes in metabolic requirements.
I have now obtained about eight singly mutants and from them I have prepared a number of double mutants giving about 18[?] in all.
Following a treatment with about 20,000, a period of incubation in complete medium and penicillin treatment I obtained 1-3 mutant cells from about 20,000 survivors from the x rays. Thus my mobility to restart them before probably arose because of their so few numbers.
About nine mutations are about all that have appeared. In other words the same mutations keep occuring over and over again. One or two mutants are of interest in [. . . ] in a single step double requirements appear. A need for adenine and thiamine appeared together and (anginine and urasil) has appeared on several occasions. In another case a strain requiring methanine was irradiated. On investigation of the double mutants one was found to need thiamine and tryptophane but not methionine. This latter may be due to an impure culture at the start since I did not start at that stage with a single cell.
I now intend to investigate each of these mutant cultures and to see if there are any differences in t heir susceptibility to various drugs. I am very grateful to you for your suggestions which have helped me to reach this stage.
Your sincerely,
John S. Loutit
Metadata Last Modified Date:
Linked Data:
RDF/XML     JSON     JSON-LD     N3/Turtle     N-Triples