S1c). In brief, the autotransporter MisL involved in intestinal colonization (Dorsey et al., 2005), its regulator MarT (Tükel et al., 2007) and an unknown putative transcriptional regulator (STY4012) are inactivated in S. Typhi. SPI-4 is a 24 kb fragment located next to a potential tRNA-like gene at centisome 92 (Fig. S1d) and involved in adhesion to epithelial cells (Wong et al., 1998).

SPI-4 harbours the siiABCDEF gene cluster encoding a type one secretion system (T1SS) for SiiE, a giant nonfimbrial adhesin of 595 kDa (Morgan et al., 2004; Gerlach et al., 2007; Morgan et al., 2007). SiiE mediates a close interaction with microvilli found on the apical side of epithelial cells, thereby aiding efficient this website translocation of SPI-1 effectors required

for apical membrane ruffling (Gerlach et al., 2008). SiiE is encoded by one ORF in S. Typhimurium (STM4261), but is segmented into two ORFs in S. Typhi (STY4458 and STY4459) because of a stop codon, also present in S. Typhi strain Ty2 (Fig. S1d) (Deng et al., 2003). This suggests that siiE is a pseudogene in S. Typhi (Parkhill et al., 2001; Morgan et al., 2004), which correlates with a loss of function for an adhesin that contributes to intestinal colonization by S. Typhimurium (Morgan et al., 2007). SPI-5 is an island <8 kb in size, inserted next to the serT tRNA gene at centisome 25, and is required for enteropathogenicity (Wood et al., 1998). SPI-5 encodes effectors of both SPI-1 and SPI-2. No difference is observed KU-57788 in vitro between the two serovars, except that an additional ORF (STY1114) is predicted to encode a transposase in S. Typhi (Fig. S1e). SPI-6 is located next to the aspV tRNA gene at centisome 7 and is a 47 kb island in S. Typhimurium (Folkesson et al., 1999; Folkesson et al., 2002), whereas

it is rather 59 kb in S. Typhi (Parkhill et al., 2001). It was previously shown that the complete deletion of this island reduced the entry of S. Typhimurium in Hep2 cells (Folkesson et al., 2002). Located on this island are a type six secretion system (T6SS), the safABCD fimbrial gene cluster and the invasin pagN (Lambert & Smith, 2008), all present in both serovars (Folkesson Cediranib (AZD2171) et al., 1999; Townsend et al., 2001; Porwollik & McClelland, 2003). A 10 kb fragment downstream of the saf operon is found only in S. Typhi, and includes probable transposase remnants (STY0343 and STY0344, both pseudogenes), the fimbrial operon tcfABCD and genes tinR (STY0349) and tioA (STY0350) (Fig. S1f) (Folkesson et al., 1999; Townsend et al., 2001; Porwollik & McClelland, 2003). The T6SS of S. Typhi contains two pseudogenes, sciI (STY0298) and sciS (STY0308), and some ORFs are missing or divergent, probably rendering its T6SS nonfunctional. Interestingly, sciS was shown to limit the intracellular growth of S. Typhimurium in macrophages at a late stage of infection and to decrease virulence in mice (Parsons & Heffron, 2005).