Abstract
In all of ten strains of H. influenzae examined prior to exposure to streptomycin a very small fraction of the bacteria formed colonies in the presence of 1,000 units of streptomycin per cc. These variant organisms possess the characteristics of bacterial mutants. 1. Different independent cultures of the same strain on different occasions, and even cultures seeded in a single test with the same inoculum, show marked variation in prevalence of resistant variants in populations of comparable size. This variation is just as great in genetically homogeneous culture sources as in heterogeneous sources. Evidence is presented for the continuous random occurrence of these resistant organisms. 2. The rate of occurrence of the resistant members is not significantly different for the ten strains studied; it varies from 2.6 x 10–11 to 7.0 x 10–11 per bacterium per bacterial generation. The results of five different tests on the same strain show comparable variation, 2.9 x 10–11 to 5.3 x 10–11. This low rate contributes evidence consistent with the mutation hypothesis. 3. Variants exhibiting resistance to 1,000 units of streptomycin per cc. transmit this trait unchanged in degree through many generations. The results obtained after twelve or more subcultures in streptomycin-free media suggest that in a portion of the colonies resistant to streptomycin an additional trait, differing from those exhibited by the parent culture, is associated; the nutritional requirements of these cultures are different.
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Selected References
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- Alexander H. E., Leidy G. MODE OF ACTION OF STREPTOMYCIN ON TYPE b H. INFLUENZAE : I. ORIGIN OF RESISTANT ORGANISMS. J Exp Med. 1947 Mar 31;85(4):329–338. doi: 10.1084/jem.85.4.329. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Brown J. H. VACUUM TUBES FOR THE STORAGE AND SHIPMENT OF BACTERIA. Science. 1926 Oct 29;64(1661):429–430. doi: 10.1126/science.64.1661.429. [DOI] [PubMed] [Google Scholar]
- Demerec M. Induced Mutations and Possible Mechanisms of the Transmission of Heredity in Escherichia Coli. Proc Natl Acad Sci U S A. 1946 Feb;32(2):36–46. doi: 10.1073/pnas.32.2.36. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Demerec M. Production of Staphylococcus Strains Resistant to Various Concentrations of Penicillin. Proc Natl Acad Sci U S A. 1945 Jan;31(1):16–24. doi: 10.1073/pnas.31.1.16. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Demerec M, Fano U. Bacteriophage-Resistant Mutants in Escherichia Coli. Genetics. 1945 Mar;30(2):119–136. doi: 10.1093/genetics/30.2.119. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Luria S. E., Delbrück M. Mutations of Bacteria from Virus Sensitivity to Virus Resistance. Genetics. 1943 Nov;28(6):491–511. doi: 10.1093/genetics/28.6.491. [DOI] [PMC free article] [PubMed] [Google Scholar]