Figure 8.

The Pst1 or Pst2 transporter is sufficient for P_i uptake under moderately high P_i conditions (1 mM), but the Pst1 transporter is required for optimal P_i uptake under low P_i conditions (200 μM) following P_i limitation. (A) P_i uptake assays of encapsulated parent strain (IU1781) and Δpst2-phoU2 (IU6550) and Δpst1-phoU1 (IU6830) mutants in 1 mM total ³²P_i in mCDM (n = 3). P_i uptake was determined as the initial rate of ³²P_i incorporation into cells in mCDM in pulse-labeling experiments described in Materials and Methods. See Tables S7 for initial rates of P_i uptake (n = 3). (B) P_i uptake assays of unencapsulated parent strain Δcps (IU1945) and Δcps Δpst2-phoU2 (K583), Δcps Δpst1-phoU1 (E595), and Δcps Δpst1-phoU1 Δpst2-phoU2 (IU5774) mutants in 1 mM P_i mCDM. See Tables S7 for initial rates of P_i uptake (n = 3). (C) P_i uptake assay of encapsulated parent strain (IU1781) and Δpst2-phoU2 (IU6550) and Δpst1-phoU1 (IU6830) mutants in 200 μM total P_i mCDM following P_i starvation for 1 h as described in Materials and Methods (n = 3). Initial rates of Pi uptake were determined with the first min of labeling and are listed in Table S8 (n = 3).