Thank you for your letter of Sept 24. Some days ago I had a discussion with Dr. Ogiusici[?] about streptomycin-resistant mutants.
I do not agree that all streptomycin-R mutants have a respiratory defect, because I had many mutants with normal respiratory
enzymes. But it is possible to get from E. coli posphyrin-negative mutants in the presence of streptomycin.
At the beginning we have isolated from E. coli ML posphyrin-less mutant
by transfer of the normal bacteria into liquid medium with increasing amounts
of streptomycin sulfate. In this way, we had much difficulty to obtain it again.
So we looked for a method to obtain regularly porphyrin-less mutants. As this mutant was sensitive to homin, we have combined
the action of homin and streptomycin on the normal bacteria.
medium: 20 gr peptone "Uclef"
2 gr glucose
5 gr Na Cl
1000 ml H20, ph 7.4
hermin solution: 5 mg hermin -> 3 ml Na2HPO4 buffer M/2. Heating at about
70-80 degrees C. After dissolution, complete the volume at 25ml(H20). Sterilisation [sic]10 min at 105 degrees C. Use always
fresh solution (1 - 3 days) at 5 degrees C
Streptomycin sulfate has been used.
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Essai[?] tubes containing 10 ml of peptone water
After 24 h, isoculum is taken in the tube with growth. So after some transfers into the next tubes we obtained a culture the
optical density of which is more less than in the normal state. Transferred on solid medium, the mutant gives very small
The same mode (with mernia) of isolation but with solid medium (Petri dishes) was unsuccessful.
We have obtained the posphyrin-negative mutants from E. coli M.L. ; B ; K-12 (CGoo); but we could not get them from K-12(112)*.
We do not know the mechanism of the appearance of such mutants. This problem has not been studied.
KW: streptomycin-resistance and porphyrin negative; Schaeffer (?);
see papers in CRAS or CRSB?
[has this been corroborated? catalase-deficient?]
I must have wondered if it was a plsmid cure.