Transformation Reactions Between Pneumococcus and Three Strains of Streptococci

Abstract

Pneumococci were caused to become streptomycin-resistant by D N A extracts of resistant mutants of the 2 strains of streptococci. In addition, resistance to optochin, which occurs naturally in these streptococci, was conferred on pneumococci by exposure to streptococcal extracts. Materials and Methods Strains of Pneumococcus.--II-D39S: an encapsulated strain of pneumococcus Type II.II-R36NC: a colonial variant of the rough strain II-R36. ILR36 was derived originally from strain II-D39S.Strains of Streptococcus.---42 different strains of streptococci were exposed to DNA extracts of streptomycin-resistant (St r) pneumococci. Of these only 2 related strains of viridans streptococd, strains D and N'BSI, were transformed to streptomycin resistance. The following streptococci were not transformed: Streptococcus kemolyticus, Group A, 12 strains; Sir.* This work was supported in part by a grant from the National Institutes of Health, United States Public Health Service.l In this paper the term homologous designates reactions between strains of the same bacterial species (homotransformation); the term hderologous refers to reactions between different species (heterotransformation). A third expression, autologo~ (autotransformation), is used to indicate reactions taking place between representatives of the same strain of a bacterial species.

Extent of Horizontal Gene Transfer in Evolution of Streptococci of the Salivarius Group

“…Natural transformation has been described for S. pneumoniae and several viridans streptococci, such as S. mutans and Streptococcus sanguinis (1,20,44), and plays an important role in generating the high levels of genotypic diversity in these species. Recombinational events are responsible for the dissemination of genes encoding virulence factors, such as antibiotic resistance markers, quinolone resistance, immunoglobulin A1 protease, and competence-stimulating peptide (5,21,25,45,54). Altered penicillin binding protein genes are directly involved in penicillin resistance, and DNA sequences closely related to them appear to have been distributed horizontally between S. pneumoniae and viridans streptococci (12,13,22).…”

Competence for genetic transformation in encapsulated strains of Streptococcus pneumoniae: two allelic variants of the peptide pheromone

“…Indeed, it has never been established just what proportion of pneumococcal isolates is transformable. This fraction has been difficult to assess, both because the pneumococcal capsule reduces or abolishes competence for genetic transformation (3,5,7,14,20,25) and because the optimal conditions for competence vary between strains.Competence for transformation in pneumococcus is not constitutive but is regulated by a quorum-sensing pheromone signal (23, 24). It was previously shown that culture supernatants from one strain, Rx1 (16), activate some other strains to competence and can induce competence in some encapsulated strains but not in others, including the type 3 strain A66 (25), even though an unencapsulated derivative of that strain is transformable (22).…”

“…Indeed, it has never been established just what proportion of pneumococcal isolates is transformable. This fraction has been difficult to assess, both because the pneumococcal capsule reduces or abolishes competence for genetic transformation (3,5,7,14,20,25) and because the optimal conditions for competence vary between strains.…”

Studies of Cellular Defense Against Infection. 1. Transformation During Mixed Pneumococcal Infection of Mice. 2. Antiphagocytic Effect of Influenza Virus on Leukocytes

“…Both pneumococci and streptococci are frequently abundant in the upper respiratory tract of man, and these organisms are capable of both intra-and inter-species exchange of genetic determinants of virulence and antibiotic susceptibility (1)(2)(3)(4)(5)(6)(13)(14)(15)(16)(17). Therefore, the natural setting exists in both health and disease for transformation to occur.…”