FIG. 10.

Model of regulation of the L. pneumophila Icm/Dot pathogenesis system. The three two-component systems (CpxRA, PmrAB, and LetAS) which were found to be involved in the regulation of pathogenesis-related genes and/or phenotypes are shown. The environmental signals sensed by CpxA and PmrB are currently not known, and the phosphorylation of these components is expected to activate by transfer of the phosphate group to the cognate response regulators CpxR and PmrA, respectively, which then activate or repress the transcription of their target genes. The target genes of CpxR and PmrA overlap in some cases, but only CpxR was found to control the expression of icm/dot genes; both regulators control the expression of IDTS-encoding genes. No target genes are currently known for the LetA-CsrA regulatory cascade. The dotted line indicates connections that might be indirect.