Dear Dr. Kikkawa: April 15, 1952 In response to your letter of April 1, I enclose four strains of E. coli: K-12, 58-161; W-1177; and W4.485. The first three of these are described in my papers. trr-1177 is you are not otherwise familiar with it is a multiple marker stoukr T-IFBl- Lacl- Mall- Gal- Mtl- Xyl- Sr Vlr , useful for recombination studies. We do not have any other auxotrophic mutants that would be pertinent to your investigations; as explained in my last letter we have not emphasieed the development of stocks for biochemical genetiws. I trust you will have no difficulties in securing addtiional mutants from K-12 or other strains. W-l485 is an indicator strain, sehsitive to the phage lambda carried by K-12. It is d&rectly derived from K-12. I have recently rece&ved a request for these two strains from your compatriot: Professor Itaru WatanabPlg at the Institute of Science and Technology, University of Tokyp; 856, Komaba, Meguro-ku. I would appreciate the favor if you would forward subcultures to him with my compliments. I hope you have no difficulties in reviving the strains. Simply open the tubes and transfer the paper strip to broth; the granules will do no harm. Yours sincerely, Joshua Lederberg P.S. I will be pleased to hear if you have any success intercrossing K-12 with your strains.