FimV, ParC and ParP coordinate polar location of the chemosensory arrays in Pseudomonas putida

Motile bacteria often rely on chemotaxis systems to promote directional movement in response to specific environmental signals. The chemotaxis machinery is typically arranged in highly ordered polar arrays containing an assortment of chemoreceptors and signal transduction proteins. Pseudomonas putida is a polarly flagellated soil bacterium that displays a chemotactic response towards numerous organic compounds present in the rhizosphere. In this work we demonstrate the involvement of the polar landmark proteins FimV, ParC and ParP in the polar assembly of the flagellar motility-associated chemosensory arrays. Confocal microscopy of fluorescent protein fusions and image analysis provide evidence that FimV, ParC, ParP are sequentially recruited to the new cell pole during the cell cycle. This recruitment hierarchy is supported by the observations that FimV is required for ParC localization and FimV and ParC stimulate ParP localization. Bacterial two-hybrid assays suggest the involvement of direct interactions between the three proteins. Our results also show that ParC displays a pole-to-pole oscillatory behavior that results in asymmetric inheritance after cell division. Analysis of the location of the chemoreceptors Aer1 and Aer2 and the histidine kinase CheA illustrates the central role of ParC and ParP in the assembly of polar chemosensory arrays, as both proteins are required for polar recruitment of Aer1 and Aer2 and further promote stable association between CheA and the chemoreceptors at the cell poles.