PENICILLIN 



97 



quently subjected to X-ray irradiation at the Carnegie Institution in Cold 

 Spring Harbor by Dr. Demerec and co-workers and an induced mutation, 

 designated X-1612 (Col. PI. II), was developed which produced yields of 

 penicillin up to 500 u/ml. when tested in 80 gallon fermenters at the Uni- 



lAWi^^mi^/mma^B 



Fig. 29. A, Typical penicillus of FeniciUium chrysugemim, NRRL 1951. B, Char- 

 acteristic penici'llus of natural variant, XRRL 1951. B25. Note the irregularity in 

 the arrangement, form, and size of parts in the latter structure, X 750. (After Raper 

 and Alexander, Jour, of The Elisha Mitchell Scientific Society, 61, 1945.) 





B 



Fig. 30. Variant substrains of Penicillium chri/sogenum, NRRL 1951. B25, isolated 

 from week-old shaken-flask cultures in penicillin production studies. See fig. 26B. 



versity of Wisconsin by Johnson et al. (1946). Finally, conidia of strain 

 X-1612 were irradiated with ultra-violet at Wisconsin and a mutation, 

 designated Q-176, was developed by Backus, Stauffer, and Jolinson (1946) 

 which produced yields up to 900 to 1000 u/ml. As each of these higher 

 yielding strains appeared, they were quickly adopted by penicillin manu- 



