Effect of R Factors on the Virulence of Their Host Bacteria

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  • Ｒ因子の宿主細菌毒力におよぼす影響　　赤痢菌由来Ｒ因子をもつネズミチフス菌ＬＴ―２株のマウスに対する毒力
  • R インシ ノ シュクシュ サイキン ドクリョク ニ オヨボス エイキョウ セ
  • 赤痢菌由来R因子をもつネズミチフス菌LT-2株のマウスに対する毒力について

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Various R factors were transferred from Shigella to Salmonella typhimurium LT-2 to examine the effect of these factors on the virulence of this organism for mice. The 50% lethal dose of the R+ strains of LT-2 varied from strain to strain. No correlation could be found between changes in virulence and those in character of any R factor.<BR>An R factor that had rendered the host strain the least virulent was subjected to further studies. The R factor carried by this strain was transferred to wild type LT-2. R+ strains thus obtained were examined for several respects. They varied again in virulence from strain to strain. Then, they were examined for the structure of the cell wall by the aggulutination test with antisera against the known wall polysaccharide mutants of LT-2, as well as by the test of susceptibility to bacteriophage specific for a cell wall component. The results obtained clearly indicated that the less vilulent strain carrying the R factor lacked some of the polysaccharidecomponents of the cell wall which might determine the virulence of the strain. In relation to this, the R factor transferred to the LT-2 mutants of known wall polysaccharide deficiency did not increase the low virulence of its host bacterial strain.<BR>Thus, it was concluded that the decrease in virulence of the R+ strains of S. typhimurium LT-2 was not caused by the function of any R factor, but by the nature of the wall polysaccharide of the host bacteria which might be advantageous for receiving the transfer of R factors.

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