<i>lovK/lovR</i> regulation of <i>hfiA</i> expression and surface adhesion.

A) The dimorphic bacterium C. crescentus builds a polysaccharide-based adhesin known as the holdfast (orange) at one cell pole, which mediates irreversible surface attachment. B) Transcription of the holdfast inhibitor, hfiA, is regulated by developmental factors [14], flagellum synthesis [15], and environmental response systems [14] including the LovK/LovR two-component system [14]. The goal of this study is to understand the mechanism of hfiA transcriptional regulation by LovK/LovR. C) Characterization of hfiA expression, surface attachment and holdfast development in wild-type (WT), lovK/lovR overexpression (lovK++lovR++) and lovK(H180A) strains. Left top: β-galactosidase activity in strains carrying a PhfiA-lacZ transcriptional fusion. Right top: Crystal violet staining of surface attached cells after growth in polystyrene wells. Bottom: Representative images of cultures where the holdfast was stained (white) with fluorescent Wheat Germ Agglutinin. Strains were grown in defined M2X medium. Bars represent mean ± s.d.; n = 6 for β-galactosidase assay and n = 8 for crystal violet stain.