Acta Microbiologica 11. (1964)
4. szám - Balassa, R.–Gábor, M.: Transformation of Streptomycin Markers in Rough Strains of Rhizobium lupini. Transformation of Streptomycin-Dependence
TRANSFORMATION OF STREPTOMYCIN MARKERS IN ROUGH STRAINS OF RHIZOBIUM LUPIN I TRANSFORMATION OF STREPTOMYCIN-DEPENDENCE By Rózsi Balassa* and Magda Gábor Institute of Genetics (Director: B. Györffy^, Hungarian Academy of Sciences, Budapest (Received June 1, 1964) Summary. The transformation of streptomycin-dependence in rough strains of Rhizobium lupini has been studied. (i) The transformation frequency of streptomycin-dependence is very low, 0.0002 to 0.000001 per cent in cases of “heterologous” transformation, and 0.0004 to 0.024 per cent in the case of “homologous” transformation. (ii) The markers of streptomycin-resistance and dependence can be transferred both separately and together. (iii) The same preparation of DNA is able to transfer both a stable and an unstable dependence. (iv) The level of streptomycin-dependence or resistance obtained by transformation is different in the different groups of transformants, one group reaching the original level of the donor, the other showing a lower level. (v) Among the transformant colonies the large ones are resistant, the normal and small ones are either dependent or resistant. (vi) It has been concluded that in Rhizobium the mutational sites of streptomycindependence and resistance are localized in one complex locus. Genetic analysis of the difference between the single-step and multistep type of mutation at a high level of streptomycin-resistance has been performed by transformation experiments with Diplococcus pneumoniae [6, 8, 11], recombination with E. coli [14], and transduction experiments with S. typhi murium [15, 16]. Genetic analysis of streptomycin-dependence has also been carried out by recombination experiments with E. coli К-12 [5, 10, 13], and transduction with E. coli [7, 9] and S. typhi murium [5]. As the analysis of the locus of streptomycin-dependence was made only by Hashimoto by means of transformation with Diplococcus pneumoniae [6], our aim was to study (1) whether it was possible to transform with the DINA of singlestep, highly resistant streptomycin-dependent mutants of the rough, streptomycin-sensitive strains of Rhizobium lupini [4] and (2) whether or not the working hypothesis of Demerec et al [5], Newcombe and Nyholm [10], i.e. that resistance to high concentrations of streptomycin, and dependence on streptomycin are controlled by alleles of the same complex gene locus, or by two loci in very close linkage, would be valid for Rhizobium? * Deceased in 1960.