Involved in the system for phosphate transport across the cytoplasmic membrane. The ability of PstS to bind phosphate may allow it to acquire phosphate from its host. Forms long appendages distinct from flagella or pili on the cell surface in approximately 1% of cells, when overexpressed more cells form more appendages. Suppressed by inorganic phosphate. Strains are still able to make extracellular appendages that include alkaline phosphatase L (phoA2, protein DING). Belongs to the PstS family.