Ions are essential nutrients for any forms of Life. In particular, phosphate is indispensable, as a key component of biomolecules (e.g. DNA), yet rare nutrient in the environment, being mostly immobilized as rocks. In fact, phosphate is both an essential nutrient, and an environmental pollutant used in agriculture and causing eutrophication. Microbes have huge needs for phosphate (cytoplasmic concentrations is ~10mM), and organisms have evolved sophisticated strategies to uptake phosphate from depleted environments. Our group is interested in the molecular mechanism of phosphate transport by the Phosphate Specific Transporter (Pst) . The competition for phosphate between organisms is intense, and therefore the environmental phosphate concentration is a key stimuli that regulate numerous bacterial functions, including growth and virulence.