FIG 4.

Regulation of the T4P motors and directional motility. (A) A model depicting regulation of the T4P motors. The Hmp chemotaxis-like system establishes polarity of T4P activation by modulating the interaction of HmpF with the motors at one side of each cell and is also indirectly sensitive to light via alterations in membrane potential. The Ptx system contains a broad-spectrum power sensing cyanobacteriochrome MCP and is required for positive phototaxis. The influence of the Ptx system on T4P activity may be modulated by the PatA-type response regulator PtxA. (B) Fluorescence micrographs depicting cellular autofluorescence, PilA immunofluorescence, lectin staining of HPS, and a merged image of all color channels (as indicated) for a hormogonium filament.