Occurrence of streptomycin-dependent mutations in a streptomycin-resistant culture of Diplococcus pneumoniae

Mishra, A. K.; Ravin, Arnold W.

doi:10.1128/jb.91.3.1389-.1966

Cited by 3 publications

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“…Their strains had a greater degree of dependence than strains with the first mutation described here which formed as many colonies in agar without streptomycin as with it. Ravin and Mishra's two strains of pneumococcus formed far fewer colonies in agar without streptomycin (12), and their strain of streptococcus could not grow at all in its absence (15).…”

Section: Discussionmentioning

confidence: 97%

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Interaction of Mutations Affecting Growth Rate and Resistance to Streptomycin in Pneumococci and Streptococci

1966

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A strain of Streptococcus (Viridans group) was shown by transformation reactions to be the carrier of two interacting mutations. One produced resistance to streptomycin and a slow rate of growth; the only effect of the second was an increase in growth rate when it was added by transformation to streptococcal strains that had already been transformed to bear the first. Similar modifying mutations were observed in strains of streptococci and pneumococci into which the first mutation had been introduced by transformation.

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Section: Discussionmentioning

confidence: 97%

“…In E. coli (14) and in pneumococcus and streptococcus (11,12,15), most mutations concerned with resistance to streptomycin, or dependence on it, are at the same locus. When separable by recombination, they are nevertheless very close together.…”

Section: Discussionmentioning

confidence: 99%

Interaction of Mutations Affecting Growth Rate and Resistance to Streptomycin in Pneumococci and Streptococci

1966

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“…The dependent strain designated str-d2 has an optimal streptomycin requirement like that of str-dl, but the latter strain resists higher concentrations of streptomycin less well than str-d2. The str-d2 mutation arose in a strain already possessing the str-r3 mutation, from which it was separated by recombination (MISHRA and RAVIN 1966). An erythromycin-resistant marker, ery-r2 (conferring resistance to 1 pg/ml erythromycin; GREEN 1959;RAVIN and IYER 1961), was introduced into the streptomycin-resistant and dependent strains to be used as donors.…”

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Genetic Linkage of Streptomycin-Dependence and Resistance in Pneumococcus

Mishra¹,

Ravin²

1966

Genetics

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A spontaneous mutation conferring dependence upon streptomycin for growth was found in a Group A strain of streptococcus, and was successfully transferred into pneumococcus ( RAVIN and MISHRA 1965). Subsequently, a dependence-conferring mutation was discovered in a streptomycin-resistant strain of pneumococcus (MISHRA and RAVIN 1966). These discoveries were fortunate for several reasons. First of all, although streptomycin-dependence mutations are not at all rare in wild-type (streptomycin-sensitive) strains of many species of bacteria, they are practically nonexistent in the sensitive strain of pneumococcus ( RAVIN and MISHRA 1965). Secondly, the genetic property of streptomycindependence lends itself to reciprocal transformations, for sensitive cells can be selected in the presence of a predominantly dependent population, and dependent cells can be selected in the presence of a predominantly sensitive population. Reciprocal transformations, in turn, make possible multi-factor crosses in which the complete variety of recombinant types can be selected. Finally, a number of streptomycin-resistance mutations have already been mapped in the pneumococcus (ROTHEIM and RAVIN 1961, 1964), so that the opportunity exists for determining the position of the dependence-conferring mutations in relation to the resistance-conferring mutations.The results of a genetic investigation of the two dependence-conferring mutations, str-dl and str-d2, are presented in this report. MATERIALS AND METHODSStrains:-The streptomycin-sensitive (str-s) strain of pneumococcus used in these experiments was the capsule-deficient strain SIII-1 (EPHRUSSI-TAYLOR 1951). The streptomycin-resistance mutations used were str-rl, str-r2, str-r3, str-r42, str-r48 and str-r51, which are genetically related to each other as shown in Figure 2. Mutations str-rl, str-r2 and str-r3 arose spontaneously in the SIII-1 strain and confer resistance to streptomycin concentrations up to 6000,300 and 150 pg/ml, respectively (BRYAN 1961). Mutations str-r51 (conferring resistance to > 10,000 ,ug/ml) and str-r42 (conferring resistance to 30 pg/ml) both originated by secondary mutation in the singlestep mutant str-r41 (which confers resistance to 3000 pg/ml; ROTHEIM and RAVIN 1%).Mutation str-r48 (conferring resistance to 150 pg/ml) arose as a secondary replacement of mutation str-r36. The streptomycin-dependent strain designated str-dl has an optimal requirement for 5(x)-1000 pg/ml streptomycin, and was obtained, as previously mentioned, by transfer of 'a single-

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Merodiploid Ribosomal Loci Arising by Transformation and Mutation in Pneumococcus

Ravin

Takahashi

1970

J Bacteriol

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Merodiploid states have been detected in the ery and str loci of the pneumococcal genome. They are associated with particular mutations ( ery-r10 and str-d2 ) which add to, rather than replace their homologous sites during deoxyribonucleic acid (DNA)-mediated transformation. Markers at linked sites do not become diploid at the same time. The heterozygous condition thus produced is maintained during cell reproduction. However, in the case of the ery merodiploid at least, segregation of haploid types does occasionally occur. The transforming properties of DNA isolated from the merodiploids, taken together with the segregation patterns of the merodiploids, reveal the heterozygous condition. The merodiploid condition can be transferred via a single molecule of DNA, which can be explained by assuming that both alleles at the diploid site are integrated into the linear continuity of the bacterial chromosome. In the case of the ery merodiploid, two distinct, relatively stable but interconvertible states are recognizable. Their interconvertibility, as well as the segregation of hapliod descendants, can be explained as the result of occasional pairing of the duplicated regions with loss of one of these duplicated regions by recombination.

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Occurrence of streptomycin-dependent mutations in a streptomycin-resistant culture of Diplococcus pneumoniae

Abstract: Attempts to find streptomycin-dependent (str-d) mutations in the sensitive SIII-1 strain of Diplococcus pneumoniae have been unsuccessful, for, if they occur at all, such mutations must arise with a frequency of <10-"1 (A. W. Ravin and

Cited by 3 publications

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Interaction of Mutations Affecting Growth Rate and Resistance to Streptomycin in Pneumococci and Streptococci

Interaction of Mutations Affecting Growth Rate and Resistance to Streptomycin in Pneumococci and Streptococci

Genetic Linkage of Streptomycin-Dependence and Resistance in Pneumococcus

Merodiploid Ribosomal Loci Arising by Transformation and Mutation in Pneumococcus

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