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Adhesion-Dependent Upregulation of Bacterial Genes, Page 1 of 2
< Previous page Next page > /docserver/preview/fulltext/10.1128/9781555817800/9781555812638_Chap09-1.gif /docserver/preview/fulltext/10.1128/9781555817800/9781555812638_Chap09-2.gifAbstract:
There are many studies showing upregulation of genes in vivo. Whether adhesion is required for the activation of many these genes is not known. In a few cases, however, it has been shown that adhesion itself activates gene expression. The PilC1-mediated contact then activates the contact regulatory element of Neisseria (CREN) site within the promoter, which induces expression of bacterial genes for a second stage of the process. In this step, more PilC1 adhesin molecules are expressed, eventually leading to the presentation of PilC1 adhesin at the pilus tip. This step is followed by upregulation of the machinery for intimate attachment associated with attaching/effacing lesions and concomitant downregulation of pilus expression. A CREN-like element also participates in the intimate-adhesion step of the process. It appears that the Opc and Opa proteins may also be involved in some aspects of the adhesion process. The target cell receptor involved in PilC1-mediated adhesion is the CD46 glycoprotein. That the outer membrane form of PilC1 could mediate adhesion in vitro was shown by centrifuging nonpiliated bacteria onto epithelial cells. The few examples provided in this chapter show that this phenomenon does occur, but the true extent to which the process of adhesion activates bacterial gene expression remains to be more fully explored.