SHELLEY PAYNE

..Transcription of fur, encoding the iron-responsive transcriptional repressor of bacterial iron acquisition, was also repressed anaerobically in an ArcA-dependent manner...

..This regulation is mediated by the repressor protein Fur and the small RNA RyhB...

..cholerae TonB1. These data suggest that the TonB box -1 position controls productive interactions with V. cholerae TonB1...

..The effects of oxygen are also seen in infection of cultured cells by Shigella flexneri; the Sit and Iuc systems support plaque formation under aerobic conditions, whereas Feo allows plaque formation anaerobically...

..cholerae. Consistent with this observation, the fur mutant competed poorly with its wild-type parental strain for colonization of the infant mouse gut...

..These data indicate that the virulence defect in MBG40 is not due to the loss of irgA function and that irgA is unlikely to be an important virulence factor...

..The Sit system is also required for virulence in a mouse lung model. The sitA mutant was able to infect the mice and induce a protective immune response but was avirulent compared to its wild-type parent strain...

..Regulation of virB by RyhB implicates iron as an environmental factor contributing to the complex regulation of Shigella virulence determinants...

..These results demonstrate that the acid sensitivity defect of the S. flexneri fur mutant is due to repression of ydeP by RyhB, most likely via repression of evgA...

..flexneri invasion and plaque formation...

..A V. cholerae vciB mutant did not exhibit any growth defects in either in vitro or in vivo assays, possibly due to the presence of other systems with overlapping functions in this pathogen...

..The redundancy in iron transport systems has made it more difficult to determine the role of individual systems in vivo and in vitro, but it may reflect the overall importance of iron in the growth and survival of V. cholerae...

..These data indicate that V. cholerae RyhB has diverse functions, ranging from iron homeostasis to the regulation of biofilm formation...

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..However, a mutant defective in the vibriobactin, Fbp, and Feo systems was not attenuated in a suckling mouse model, suggesting that at least one other iron transport system can be used in vivo...

..ShuS did not appear to store heme for future use...

..HutZ may act as a heme storage protein, and it may also function as a shuttle protein that increases the efficiency of heme trafficking from the membrane to heme-containing proteins...

..DegP was also required for efficient polar IcsA localization in E. coli expressing icsA. In addition, the growth or survival of SM1100 was compromised compared to that of the wild type at elevated temperatures and in acidic conditions...

..Therefore, the three periplasmic folding factors DegP, Skp, and SurA were all required for IcsA localization and plaque formation by S. flexneri...

..The presence of genes encoding homologs of dendritiformis sibling bacteriocin in other bacterial species suggests that this mechanism for self-regulation of colony growth might not be limited to P. dendritiformis...

..In contrast, the cognate putative ATPases were required for each process and could not substitute for each other...

..Overall our data demonstrate that O157:H7 and non-O157 serovars, in particular O26:H(-)/H11 and O103:H2, use distinctly different strategies for obtaining iron, and suggest two evolutionary distinct lines of enterhaemorrhagic E. coli...

..Since human endogenous retroviruses also encode Sags, these studies have broad implications for pathogen-induced responses in mice and humans...

..Because no system comparable to Feo is found in the human, this iron transport system may represent a new class of targets for antimicrobial therapy. ..

..Results obtained from this study will provide basic information on genetics and regulation of potential virulence factors in an important group of pathogens and will provide data useful in design of potential vaccine strains. ..

..The third Specific Aim is to use our mutant collection, together with other reagents, to determine which transport systems are used during specific environmental conditions, and during growth in the vertebrate host. ..

..Our fourth specific aim is to assess expression of iron transport and other genes during intracellular growth and during infection by using microarray technology. ..

..abstract_text> ..

..flexneri invading or multiplying within host cells. This provides a tool for determining expression of virulence factors in vivo and, in the long term, will be a useful technique in design and analysis of potential vaccine strains...

..Genetic studies will primarily be concerned with the involvement of phage or plasmids in virulence of Shigella...