Table 1

Characterization of macrophage-inducible genes (mig). DNA fragments (0.2 to 1.2 kb) with intracellular-dependent activity trapped by differential fluorescence enrichments (Fig. 1) were sequenced and compared with the available DNA sequence databases at the National Center for Biotechnology Information (NCBI). Putative functions were assigned either when a particular gene had been previously described in S. typhimurium or when the function of a close homolog (>50% amino acid identity) had already been determined. For promoter regions with no significant homology to previously described genes or with homology to genes with unknown function, flanking DNA was isolated by recombinational cloning (10) and sequenced. Five ORFs downstream of macrophage-inducible promoters were inactivated either by insertion of a kanamycin resistance gene flanked by transcriptional terminators (ΩKn) or by insertion of the suicide vector pGP704 (Ampr) into coding regions (27). ND, not determined.

Con- struct HomologyFold induction in macrophages*Protein features or putative functionRegulationRole in virulence
mig-1 § aas 16.4Phospholipid recyclingOmpR/EnvZ (40)ND
mig-2 pagA/ugd 16.6Capsule biosynthesisPhoP/PhoQNo(29)ND
mig-3 31.1Phage-derived genesPhoP/PhoQND
mig-4 phoS 9.4Phosphate transportPhoB/PhoR (20)NoThis study1.7  ± 1.2
mig-5 24.1Virulence plasmid lipoproteinPhoP/PhoQYesThis study0.15 ± 0.01
mig-7 yjbA (orf o156) 15.2Inner-membrane proteinPhoP/PhoQNoThis study0.77 ± 0.5
mig-10 ssaH 442.9Type III secretionSsrA/SsrBYes(15,16)<0.001
mig-13 orf f198 8.0Transmembrane proteinNoThis study1.6  ± 0.25
mig-14 22.4PhoP/PhoQYesThis study0.05 ± 0.02
mig-20| 12.6ND
mig-23 himA 14.9Gene regulationYes(4)ND
mig-26 exc(traT) 9.4Plasmid exclusion proteinPhoP/PhoQSerum resistance(21)ND
mig-29 hsIU 23.7Stress-inducible proteasePhoP/PhoQND
mig-30 11.1PhoP/PhoQND
  • * mig activity inside cells was determined as described in Fig. 1G.

  • Macrophage induction of the variousmig::gfp gene fusions was tested in wild-type, PhoP, and OmpR S. typhimuriumbackgrounds. In addition, the expression ofmig-10::gfp was tested in a S. typhimurium background bearing a miniTn5Km insertion in eitherssaR or ssrB (15).

  • The role in virulence of the various mig genes was determined either from previous work (Ref.) or from information derived from insertionally inactivated mig (28). The SPI-II mutant P3F4 (15) was included as a control.

  • § mig-1 represents a DNA fragment spanning the intergenic region between galR andaas and is present ∼400 bp upstream of theaas start codon.

  • | mig-20could not be isolated by recombinational cloning.