Additional plasmid-encoded proteins such as PhoN1 and PhoN2 were decreased in abundance in vivo. PhoN2 was reported to hydrolyze dNTPs and modulate the localization of IcsA at the click here bacterial cell surface [59]. OspC2, IpaB and VirB were identified as immunogenic when probed with a piglet antiserum in a 2D Western blot [15], suggesting that these proteins could form potential vaccine targets for the prevention of shigellosis. The Ipa proteins are known to be transiently associated with the cell surface and therefore are likely to

contribute to the altered SD1 cell surface in the host gut environment. selleck kinase inhibitor We assume that other proteins likely secreted via the TTSS (OspC2, OspC3) are at least transiently cell surface associated. Abundance changes of the TTSS virulence factors correlated well buy Verubecestat with the altered changes in the OM/cell surface proteins in vivo. We are tempted to speculate that the previously mentioned OM remodeling efforts benefit the adaptation of SD1 to the host cell invasion process via enhanced abundance of TTSS effectors in the cell envelope. However, our data do not support

uniformly increased abundances of all detected TTSS proteins in the SD1 cell envelope in vivo. The virulence of Shigella species is of the order S. dysenteriae > S. flexneri > S. sonnei > S. boydii. SD1 infection has a limited diarrheal phase with a sudden onset of acute dysentery, which could be explained by the expression of the potent virulence factor Shiga toxin (Stx) [14]. Shiga toxin subunit A (StxA) was detected only in vitro, while Shiga toxin subunit B (StxB) was detected both in vitro Bcl-w and in vivo, with StxB increased in abundance in vitro. As Stx is a secretory protein [14], the abundance levels of this protein are not readily obvious from proteomic profiling of cell lysates. It is of interest to examine whether the Shigella T2SS secretes other virulence factors in addition to the Shiga toxin. T2SS subunits were of very low abundance in SD1 cells according to this survey. Other proteins involved in Shigella pathogenicity are the O-antigens which are highly

diverse with at least 46 observed serotypes [2]. The variability of the O-antigens has been brought into context with evasion of the host immune system [60]. The small SD1 plasmid-encoded galactosyltransferase RfpB involved in the O-antigen biosynthesis was detected only in vivo, while other enzymes such as RfaD were increased in vivo. Enzymes potentially known to contribute monosaccharides (galactose and rhamnose) to the biosynthesis of the O-antigen sugars were also increased in vivo, including LacZ, GalE/K/M/T, RfbC, MelA, ManA and KdsB. Further studies are necessary to determine whether increased carbohydrate metabolism is functionally coupled to altered biosynthesis of O-antigen sugars under in vivo conditions. Conclusions The comparative global proteomic survey of S.