Genetic Exchange in Salmonella

Abstract

Genetic investigations with many different bacteria have revealed parallelisms and some contrasts with the biology of higher forms. The successful application of selective enrichment techniques to the study of gene recombination in Escherichia coli (Tatum and Lederberg, 1947; Lederberg et al., 1951) suggested that a similar approach should be applied to other bacteria. This paper presents the results of such experiments with Salmonella typhimurium and other Salmonella serotypes. The mechanism of genetic exchange found in these experiments differs from sexual recombination in E. coli in many respects so as to warrant a new descriptive term, transduction. MATERIALS AND METHODS Most of the strains of S. typhimurium were provided by Lilleengen (1948) as representative of his 21 "phage types", LT-1 through LT-22. Most if not all strains of S. typhimurium are lysogenic (Boyd, 1950), and these have provided 12 lines of bacteriophage. Other cultures were obtained from F. Kauffmann, E. K. Borman, and P. R. Edwards. All cultures were maintained on nutrient agar slants. Specific growth factor dependent mutants (auxotrophs) were obtained from ultraviolet irradiated cell suspensions subjected to the penicillin method for selective isolation (Davis, 1950a; Lederberg and Zinder, 1948). Similar mutants have been obtained in Salmonella by Plough et al. (1951) and Bacon et al. (1951). Other methods for the isolation and characterization of auxotrophic and fermentation mutants have been documented elsewhere (Lederberg, 1950; Lederberg and Lederberg, 1952). Streptomycin resistant mutants were selected by plating dense, unirradiated cell suspensions into agar containing 500 mg per L of dihydrostreptomycin. "Complete" indicator medium (EMB) was made up from the same formula as for E. coli (Lederberg, 1950). The defined eosin methylene blue medium ("EML agar") containedin g per L: sodium lactate, 2.5; (NH4)2SO4, 5; NaCl, 1; MgSO4, 1; K2HPO4, 2; methylene blue hydrochloride, 0.05; eosin Y, 0.3; and agar, 15. Difco products, penassay broth, and nutrient agar, were employed as "complete" media.

Inorganic Nanoparticles as Carriers of Nucleic Acids into Cells

“…Advantages Disadvantages Viral methods [44,45,202] highly efficient [46][47][48][49][50] immunogenicity, [48,51,52] carcinogenicity, [48,51,52] inflammation [53] Physical methods electroporation [59][60][61][62][63][203][204][205] easy to perform; efficient optimization for every cell line required; a large amount of DNA is necessary microinjection [17][18][19][20][21][22][23][24]64] exact direction of nucleic acid into a single cell one cell after the other, that is, a slow, sequential method gene gun [65][66][67][68][69] useful for genetic vaccination shallow penetration of DNA into the tissue Chemical methods cationic compounds [76] easy preparation toxicity [72,75,82] recombinant proteins [56][57][58] high biocompatibility expensive polymeric nanoparticles, for example, polylactide [206,…”

“…This is the oldest method for gene transfer, first demonstrated on Salmonella in 1952. [45] Later, for gene transfer into cells, different viral vectors based on retroviruses, [46,47] adenoviruses, [48] adeno-associated viruses, [49] herpes simplex virus, [50] and other viruses were introduced. It is a most efficient method with which to introduce DNA into cells, but it carries serious risks, such as the possibility of recombination, strong immunogenicity, inflammatory response, and carcinogenicity.…”

Bacterial copper‐ and zinc‐cofactored superoxide dismutase contributes to the pathogenesis of systemic salmonellosis

“…Bacterial strains and culture S. typhimurium strains ST4/74 and ST12/75, S. dublin SD2229 and S. choleraesuis strains SCS14/74 and SCSA50 are clinical veterinary isolates Canvin et al, 1996). S. typhimurium strain C5 is highly virulent for mice (Miller et al, 1989) and S. typhimurium LT2 is a strain of low virulence for mice (Zinder and Lederberg, 1952). S. typhimurium ST4/74 invH is a strain that shows reduced invasiveness for enterocytic cells , which was used as a control in invasion assays.…”

A protocol for the combined biochemical and serological identification of the Ames mutagen tester strains as Salmonella typhimurium

“…As mentioned above, the previous investigators studying speciation of these strains [5,23] expressed a belief in the correct speciation of the tester strains in spite of the technical difficulties encountered. In contrast to many of the suspected instances of laboratory contamination with animal cells [22], the tester strains had genetic markers (his-, AuvrB, rfa, and other mutations), which permitted verification of their relationship with the parental strains and thus, by association, with ancestral strain Salmonella typhimurium LT-2 [25,26]. Our speciation is thus of significance not in confirming the genetic identity of the known tester strains, but rather in illustrating the principle that standard biochemical media on occasion may inadequately support the growth of certain auxotrophs, in contributing to the characterization of the tester strains, and in showing how the strains might be identified in the future in hypothetical instances of suspected laboratory-acquired infection or culture contamination.…”