Expression of Salmonella typhimurium rpoS and rpoS-dependent genes in the intracellular environment of eukaryotic cells.
Adaptation to the intracellular environment of host cells is crucial for the pathogenesis of Salmonella infections. The alternative sigma factor RpoS is a global regulator of gene expression during starvation and stress conditions and is required for virulence in Salmonella spp. We have used lacZ reporter fusions to rpoS and rpoS-dependent genes to study rpoS regulation after entry of Salmonella typhimurium into macrophages and epithelial cells. The results demonstrate that expression of an rpoS::lacZ translational fusion increases rapidly in S. typhimurium after phagocytosis. Activity of RpoS also increases after bacterial entry into both macrophages and epithelial cells, as demonstrated by the induction of the rpoS-regulated genes katE and spvB. A control rpoS-independent promoter for neomycin resistance does not show significant induction after cell entry. These results demonstrate that the regulatory system mediated by RpoS in S. typhimurium is activated by the intracellular environment of eukaryotic cells.
Department of Medicine, School of Medicine, University of California at San Diego, La Jolla 92093, USA.
C Y
CY
Chen
L
L
Eckmann
S J
SJ
Libby
F C
FC
Fang
S
S
Okamoto
M F
MF
Kagnoff
J
J
Fierer
D G
DG
Guiney
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D002374:Catalase / Q000235:genetics; D002460:Cell Line; D004352:Drug Resistance, Microbial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D006801:Humans; D007413:Intestinal Mucosa / Q000382:microbiology; D008264:Macrophages / Q000276:immunology / Q000382:microbiology*; D051379:Mice; D009355:Neomycin / Q000494:pharmacology; D010587:Phagocytosis; D011401:Promoter Regions, Genetic; D012486:Salmonella typhimurium / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity; D012808:Sigma Factor / Q000235:genetics* / Q000502:physiology; D014774:Virulence / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D002374:Catalase; D009355:Neomycin