Genetic Analysis of the<i>ViA-his</i>Chromosomal Region in<i>Salmonella</i>

Johnson, E. M.; Krauskopf, Barbara; Baron, L. S.

doi:10.1128/jb.92.5.1457-1463.1966

Cited by 33 publications

(19 citation statements)

References 12 publications

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“…and H52. The appearance of' the Vi antigen in hybrid H52 is due to its acquisition of the ViA determinant of' S. typhimurium as described previously (3,4). The acquisition of various combinations of S. typhimurium antigens by these S. tvphosa hybrids did not result in any observable change with regard to their mouse virulence level (mean lethal dose > 107 organisms).…”

Section: Resultssupporting

confidence: 60%

“…The donor suspension (0.1 ml) was then spread over 0.1 ml of the recipient lawn on minimal agar selective media. S. typhosa hybrids resulting from the cross between S. typhosa WR4208 and the S. typhimurium Hfr B2 were obtained in previous studies, as described elsewhere (3,4). The procedures employed for serological examination of the hybrids were essentially those described by Edwards and Ewing (2).…”

Section: Methodsmentioning

confidence: 99%

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Role of Typhoid Antigens in Protection and Pathogenicity for Mice

et al. 1974

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Swiss white mice immunized with acetone-killed vaccines prepared from strains of Salmonella typho.sa, S. typhimurium, and mouse-virulent S. typhimurium hybrids which had acquired, by conjugal genetic transfer, the S. typhosa antigens 9, Vi, and d were challenged with the S. typhimurium hybrids and with the S. tvphimurium parent strain. The results of' these experiments suggested that the Salmonella somatic antigens were important in conf'erring protection against death in this system. The S. typhosa Vi antigen did not appear to play any signif'icant role in this protection. The S. typhimurium hybrids employed in these studies did not show any loss of mouse virulence as the consequence of' acquisition of various combinations of the S. typhosa somatic, flagella, or Vi antigens, nor did S. typhosa hybrids which had acquired the somatic antigen of S. typhimurium show any increase in mouse virulence.A previous report (1) described the formation of Salmonella typhimurium hybrids expressing antigens 9, Vi. and d by genetic crosses between a S. typhimurium recipient and a S. t,vphosa Hf'r donor. These hybrids retained the same degree of' mouse virulence as their S. typhimurium parent when tested with either C57 black or Swiss white mice. Furthermore, vaccination of' mice with S. typhosa vaccines conferred significant protection against challenge by these hybrid strains but not against their S. typhimurium parent. However, no conclusions were made regarding the protective role of individual S. tvphosa antigens. In the present report, further studies with this system are described which suggest that the somatic antigens are of' primary importance in conferring protection.MATERIALS AND METHODS Mating procedures. S. typhimurium hybrids were obtained by the method previously described (1). Briefly, overnight broth cultures (Penassay broth, Difco) of donor and recipient strains were centrifuged and resuspended in fresh broth. The concentrations of cells were adjusted to approximately 108/ml for the recipient and 2 x 108/ml for the donor. The donor suspension (0.1 ml) was then spread over 0.

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Section: Resultssupporting

confidence: 60%

Section: Methodsmentioning

confidence: 99%

Role of Typhoid Antigens in Protection and Pathogenicity for Mice

et al. 1974

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“…As reported previously (4, 5), the majority of his+-selected S. typhimurium hybrids obtained from mating with S. typhosa WR4000 also inherit the closely linked genetic determinant of somatic antigen 9. Because the genetic determinant of this antigen is the allele of the somatic antigen 4 determinant of S. typhimurium (4,5,8), recombination of this locus results in loss of expression of antigen 4 by those S. typhimurium recombinants which express antigen 9. In addition, such recombinants also lose antigen 5 because this antigen cannot be expressed in strains lacking the determinant of antigen 4 (4,5,8).…”

Section: Resultsmentioning

confidence: 99%

Assay of Typhoid Vaccines with Salmonella typhosa-Salmonella typhimurium Hybrids

et al. 1973

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Salmonella typhimurium hybrids expressing the S. typhosa antigens 9, d, and Vi were constructed by genetic crosses with an S. typhosa Hfr donor. The hybrids retained the same degree of mouse virulence as their S. typhimurium parent strain, the minimum lethal dose being less than 50 organisms when tested either in C57 black mice or Swiss white mice. Vaccination of the Swiss white mice with S. typhosa Ty2 vaccines prepared by acetone treatment, alcohol treatment, or heat-killing conferred significant protection against challenge by the hybrid strains but not against their S. typhimurium parent. Both the acetone-treated and alcohol-treated typhoid vaccines were markedly more protective than the heat-killed, phenol-preserved vaccine.

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“…Vi-expressing Salmonella give rise to nonexpressing variants at frequencies no higher than can be accounted for by spontaneous mutation, and reversion of such nonexpressing variants to the expressig form is rarely seen. The results of previous studies (9,10) have shown that the genes determining Vi antigen expression in Salmonella are situated at two widely separated chromosomal loci, viaA and viaB. The viaA locus is situated near the genes determining histidine biosynthesis, his.…”

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Genetic regulation of variable Vi antigen expression in a strain of Citrobacter freundii

Snellings¹,

Johnson²,

Kopecko³

et al. 1981

J Bacteriol

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Certain strains of the genus Citrobacter exhibit a variable expression of the Vi surface antigen that appears to involve a special mechanism for regulation of gene expression. Two nonlinked chromosomal loci, viaA and viaB, are known to determine nonvariable Vi antigen expression in strains of Salmonella. To confirm the presence of analogous loci in Citrobacter and to ascertain whether either of them is involved in variable Vi antigen expression in this organism, donor strains were constructed from Citrobacter freundii WR7004 and used to transfer their Vi antigen-determining genes to ViaA- and ViaB- Salmonella typhi recipient strains. Vi antigen expression in C. freundii was found to be controlled by loci analogous to the Salmonella via genes. S. typhi recipients of the C. freundii viaA+ genes were restored to the full, continuous expression of the Vi antigen normally seen in S. typhi. Thus, the C. freundii viaA genes appeared to play no role in the variable expression of the Vi antigen. In contrast, S. typhi recipients of the C. freundii viaB+ genes exhibited the rapid, reversible alternation between full Vi antigen expression and markedly reduced Vi antigen expression that was seen to occur in the C. freundii parent. The C. freundii viaB locus was thus identified as the one whose genes are regulated so as to produce variable Vi antigen expression. Genes determining another C. freundii surface antigen, the synthesis of which is not affected by the mechanism regulating Vi expression, were coinherited with the C. freundii viaB+ genes. An invertible, insertion sequence element located within the C. freundii viaB locus is proposed to account for the regulation of variable Vi antigen expression.

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Genetic Analysis of theViA-hisChromosomal Region inSalmonella

Cited by 33 publications

References 12 publications

Role of Typhoid Antigens in Protection and Pathogenicity for Mice

Role of Typhoid Antigens in Protection and Pathogenicity for Mice

Assay of Typhoid Vaccines with Salmonella typhosa-Salmonella typhimurium Hybrids

Genetic regulation of variable Vi antigen expression in a strain of Citrobacter freundii

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