Generation of a proton motive force by the excretion of metal-phosphate in the polyphosphate-accumulating Acinetobacter johnsonii strain 210A.
The strictly aerobic, polyphosphate-accumulating Acinetobacter johnsonii strain 210A degrades its polyphosphate when oxidative phosphorylation is impaired. The endproducts of this degradation, divalent metal ions and inorganic phosphate, are excreted as a neutral metal-phosphate (MeHPO4) chelate via the electrogenic MeHPO4/H+ symport system of the organism. The coupled excretion of MeHPO4 and H+ in A. johnsonii 210A can generate a proton motive force. In membrane vesicles and deenergized cells, a membrane potential of about -70 mV and transmembrane pH gradient of about -8 mV were formed in response to an imposed outwardly directed MeHPO4 concentration gradient of 120 mV (initial value). The MeHPO4 efflux-induced proton motive force could drive energy-requiring processes, such as the accumulation of L-proline and L-lysine and the synthesis of ATP via the membrane-bound F0F1 H(+)-ATPase. In vivo 31P NMR studies of polyphosphate degradation in anaerobic cell suspensions revealed the presence of a considerable outwardly directed phosphate gradient across the cytoplasmic membrane corresponding to a MgHPO4 concentration gradient of at least 100 mV. This MgHPO4 concentration gradient was maintained for several hours. Thus, energy recycling by MeHPO4/H+ efflux will contribute significantly to the overall production of metabolic energy from the degradation of polyphosphate in A. johnsonii 210A.
Department of Microbiology, Agricultural University Wageningen, The Netherlands.
H W
HW
van Veen
T
T
Abee
G J
GJ
Kortstee
H
H
Pereira
W N
WN
Konings
A J
AJ
Zehnder
D000150:Acinetobacter / Q000378:metabolism*; D001692:Biological Transport; D004734:Energy Metabolism; D008564:Membrane Potentials; D008670:Metals / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010710:Phosphates / Q000378:metabolism*; D011522:Protons
D008670:Metals; D010710:Phosphates; D011522:Protons