Regulatory cross-talk between adhesin operons in Escherichia coli: inhibition of type 1 fimbriae expression by the PapB protein

Pathogenic Escherichia coil often carry determinants for several different adhesins, We show a direct communication between two adhesin gene clusters in uropathogenic E.coli: type 1 fimbriae (fim) and pyelonephritis-associate d pill (pap). A regulator of pop, PapB, is a key factor in this cross-talk. FimB recombinase turns on type 1 fimbrial expression, and PapB inhibited p hase transition by FimB in both off-to-on and on-to-off directions, On-to-o ff switching requiring FimE was increased by PapB, By analysis of FimB- and FimE-LacZ translational fusions it was concluded that the increase in on-t o-off transition rates was via an increase in FimE expression. Inhibition o f FimB-promoted switching was via a different mechanism: PapB inhibited Fim B-promoted in vitro recombination, indicating that FimB activity was blocke d at the pm switch, In vitro analyses showed that PapB bound to several DNA regions of the type 1 fimbrial operon, including the fim switch region, Th ese data show that Pap expression turns off type 1 fimbriae expression in t he same cell, Such cross-talk between adhesin gene clusters may bring about appropriate expression at the single cell level.