Salmonella typhimurium mutants lacking flagella or motility remain virulent in BALB/c mice.
Nonmotile flagellated (mot) and nonflagellated (fla) mutants of Salmonella typhimurium LT-2 were isolated from a collection of mutants with random Tn10-insertion mutations. Both classes of mutants were resistant to infection by the flagellotropic bacteriophage chi. The nonflagellated (fla::Tn10) mutants did not react with H antigen-specific antisera and did not possess flagella when examined by electron microscopy, and sheared-cell extracts were devoid of flagellin. The nonmotile (mot::Tn10) mutants reacted with H-specific antisera and expressed paralyzed flagella that were indistinguishable from wild-type flagella. The Tn10 insertions in strain LT-2 were mapped to loci in regions II (flh and mot) and III (fli) of the flagellar genes, and the mutations were transduced into the mouse-virulent S. typhimurium strains SR-11 and SL1344. Lack of motility reduced the ability of S. typhimurium to invade Henle cells in vitro, yet the virulence in mice of the nonmotile mutants of SR-11 and SL1344 was unaffected by the inactivity or loss of flagella. Wild-type SR-11 had a 50% lethal dose (LD50) in BALB/c mice following oral (p.o.) challenge of 2.4 x 10(4) CFU. The p.o. LD50 of the SR-11 fli-8007::Tn10 mutant was 4.5 x 10(4) CFU. The mot-8008::Tn10 mutation in SR-11 conferred paralyzed flagella and increased the p.o. LD50 in mice to 2.2 x 10(5) CFU, but this was not statistically significant. A similar increase in the p.o. LD50 was observed when the SL1344 mot-8008::Tn10 mutant was tested in mice. Wild-type SR-11 and the isogenic nonflagellated and nonmotile mutants were equally virulent in mice challenged via intraperitoneal injection.
Lockman
H A
HA
Department of Biology, Washington University, St. Louis, Missouri 63130.
Curtiss
R
R
D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics; D002874:Chromosome Mapping; D004252:DNA Mutational Analysis; D004251:DNA Transposable Elements; D004274:DNA, Recombinant; D005407:Flagella / Q000502:physiology; D005798:Genes, Bacterial; D051379:Mice; D012481:Salmonella Infections, Animal / Q000382:microbiology; D012486:Salmonella typhimurium / Q000235:genetics* / Q000472:pathogenicity / Q000648:ultrastructure
D000942:Antigens, Bacterial; D004251:DNA Transposable Elements; D004274:DNA, Recombinant