Identification of a Salmonella virulence gene required for formation of filamentous structures containing lysosomal membrane glycoproteins within epithelial cells

Murry A. Stein, Ka Yin Leung, Michael Zwick, Francisco Garcia-del Portillo, B. Brett Finlay*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

212 Scopus citations

Abstract

Salmonella species are facultative intracellular pathogens that invade epithelial cells and reside within lysosomal membrane glycoprotein (Igp)-containing vacuoles. Coincident with the onset of bacterial replication inside these vacuoles, Salmonella induce the formation of stable Igp-containing filamentous structures that connect with the Salmonella-containing vacuoles. Salmonella typhimurium SL1344::Tn 10dCm mutant strains unable to induce these structures were isolated. All contained insertions within a novel Salmonella induced filament gene A (sifA). sifA is present only in Salmonella species and encodes a protein with a predicted molecular mass of 38 kDa and an apparent molecular mass of 35 kDa. sifA is flanked by ~300 base pairs, and sifA and its flanking DNA show no homology to sequences in DNA databases. sifA is located within the potABCD operon, a housekeeping locus involved in periplasmic transport of polyamines. Fourteen-base-pair direct repeats mark the probable site of integration of sifA and its flanking DNA at the 3' end of potB. sifA and its flanking DNA have a significantly reduced G+C content (41%) when compared with the potABCD operon (51%) and the Salmonella genome (52-54%). Deletion mutant strains in sifA or in the downstream potC were constructed. ΔsifA does not produce Salmonella-induced filaments in epithelial oells, and is attenuated in mice. ΔpotC produces Salmonella-induced filaments in epithelial cells, and was fully virulent. Collectively, these results suggest that sifA arose by horizontal gene transfer into Salmonella and its product is involved in a virulence-associated intracellular phenotype related to Salmonella-induced filament formation.

Original languageEnglish
Pages (from-to)151-164
Number of pages14
JournalMolecular Microbiology
Volume20
Issue number1
DOIs
StatePublished - 1996

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