The Genetics of Transformation

SUMMARYDeoxyribonucleate (DNA) preparations from Moraxella izoialiquefuiens elicited genetic transformation of Neisseria catarrhalis recipient cells, and vice versa. The frequency was low (0.0005% transformation for the most reactive of six strains), as might be expected of an interaction between two organisms as dissimilar as a rod and a coccus. Evidence that the hereditary change (attainment by susceptible cells of resistance to 500 pg. dihydrostreptomycin/ml.) was due to transformation was provided by the typical time course of the reaction, the typical linear response to decreasing concentrations of DNA below 0.1 pg./ml., and by tests of transforming activity of DNA preparations extracted from 11 dihydrostreptomycin-resistant (str-r) strains which arose by intergeneric transformation. These DNAs had relatively high transforming activity for recipient strains of both species. Thus, the str-r region of the transforming DNA molecule from a transformant strain of M . nonliquefaciens was recognized and genetically integrated by populations of N . catarrhalis recipient cells a t frequencies as much as 10,000 times higher than those of DNA from strains of M . nonliquefmiens str-r (derived by spontaneous mutation). The results with DNA preparations from particular transformants are interpreted as indicating that the length of a DNA nucleotide sequence which is integrated by a cell during str-r transformation may differ for different cells of the same treated population.

Section: Intergeneric Transformation 375 Discussionmentioning

confidence: 99%

Reciprocal Genetic Transformation Between Neisseria catarrhalis and Moraxella nonliquefaciens

Catlin

1964

“…The physiological state of competence seems to be in some way connected with the mechanism of DNA penetration through the cell wall. Two hypotheses have been proposed to account for penetration: one termed the 'localized protoplast ' hypothesis and the other defined as the ' enzymic receptor ' hypothesis (Ravin, 1961). The ' localized protoplast ' hypothesis, based mainly on evidence provided by Thomas (1955), regards the competent cell as one having during some period of its life cycle naked areas on the surface through which DNA can penetrate.…”

Section: Introductionmentioning

confidence: 99%

On the Nature of Competence of Transformable Streptococci

Walczak

1963

200

108

SUMMARYTransformable streptococci produce an exocellular factor provoking competence under certain conditions. Non-competent cultures become competent upon addition of this factor. The kinetics of conversion is concomitant with an enzymic reaction ; the process is time and temperature dependent and the factor itself is heat sensitive. The action of the hypothetical enzyme on cells of a non-transformable streptococcus results in provocation of competence.

“…However, participation of these elements in transformation was anticipated by Ravin (1961), Nomura (1967 …”

Section: Paradoxical Inhibition 359mentioning

confidence: 99%

Paradoxical Inhibition among Bacteria. Characterization of the Phenomenon and Nature of the Genetic Process

Chakrabarty¹,

Dastidar²

1974

(pi.) manifests itself as well-defined growth of a sensitive bacterium in the centre of the zone of inhibition overlying an area of growth of the inhibitory bacterium. Bacteriocin typing medium (BTM) for Vibrio cholerae elicited p.i. for this group only. A medium for paradoxical inhibition (MPI) was devised which supported the development of p i among members of Enterobacteriaceae, Vibrio and Alcaligenes spp. at high frequency. The reacting pair of strains could belong either to the same or to different genera. Colonies of non-bacteriocinogenic strains derived from the central area of p i showed acquisition of bacteriocinogeny at high frequency. Acquisition was rapid in the beginning (up to 4 h) followed by a decline and virtual disappearance of bacteriocinogeny by I 8 h on MPI, but was substantially retained on BTM. The overall frequency of acquisition among cell populations of different strains varied between 10-1 and IO-*, and the acquired characters were stable. Acquisition did not require either cell contact or participation of phages, but depended upon extracellular diffusable agents that were DNase sensitive and RNase resistant. A mutational basis for such acquisition could be ruled out, and the process of gene transfer was considered to be transformation. The extra-chromosomal nature of the determinants of bacteriocinogeny in the bacteria studied was suggested by effective elimination of these markers by sodium dodecyl sulphate and acridine orange.