Binds 1 inorganic phosphate per subunit, required for phosphate transport (By similarity). In virulent strain MDR25, which expresses very high levels of this protein, implicated in host cell adhesion; antibody fragments against this protein decrease adhesion to host cells and increase transepithelial resistance of human epithelial cell monolayers. High-phosphate-grown MDR25 strains form smooth colonies, express less PstS, more biofilm and are less lethal in mouse infection models than high-phosphate-grown rough colonies that express more PstS, less biofilm and are more lethal in mouse infection models; whether this is phenotype is due to PstS is unknown, however feeding mice with phosphate supplements protects them from lethality. The ability of PstS to bind phosphate may allow it to acquire phosphate from its host (PubMed:18282104). In some strains (e.g. virulent clinical strain MDR25) forms long appendages distinct from flagella or pili on the cell surface: the protein is removed from the cell surface by vigorous vortexing (2 minutes) giving a cell surface sheared protein fraction. By phosphate starvation (at protein level), shown for protein in MDR25 and for RNA in MDR1. Different strains have widely differing amounts of protein that can be sheared from the cell surface, in order of decreasing quantities MDR25 >> MDR1 > PAO1 > MDR13 (PubMed:18282104). Protein sequence obtained for strain MDR1, using protein removed from the cell surface by vigorous vortexing (2 minutes) on cells grown in about 300 uM phosphate. Belongs to the PstS family.