Table 1.

Effect of Δp dissipation and ATP depletion on Pi transport in R. tropici CIAT899 and CAP45a

TreatmentStrainPi uptake (nmol of Pi/min/mg [dry wt] of cells)ATP concn (nmol of ATP/mg [dry wt] of cells)
5 μM Pi400 μM Pi
Ethanol controlCIAT89926.7 ± 3.241.8 ± 3.12.20 ± 0.20
CAP452.4 ± 0.38.8 ± 0.11.41 ± 0.31
CCCP (1 μM)CIAT89923.8 ± 1.4 (11)b 44.9 ± 2.1 (0)1.84 ± 0.08 (18)
CAP452.1 ± 0.1 (12)12.2 ± 0.1 (0)1.35 ± 0.26 (4)
Ethanol controlCIAT89910.2 ± 2.211.76 ± 1.970.305 ± 0.005
CAP452.2 ± 0.17.06 ± 0.371.03 ± 0.16
DCCD (100 μM)CIAT8990 ± 0 (100)0.43 ± 0.08 (96)0.02 ± 0.01 (93)
CAP450.034 ± 0.001 (98)0.29 ± 0.02 (96)0.09 ± 0.04 (91)
  • a −Pi cells were treated with EDTA as described in the text, preincubated with an inhibitor and then assayed to determine Pi uptake and the intracellular ATP concentration. Values are means ± standard errors based on values from two separate experiments. Cells were preincubated for 5 min in the presence of the Δp dissipator CCCP or for 45 min in the presence of the ATPase inhibitor DCCD. Using ethanol to solubilize CCCP and DCCD did have a negative effect on the overall transport rates, and therefore an ethanol control was included in all experiments.

  • b The values in parentheses are percentages of reduction in Pi transport or ATP concentration compared to the controls.