Premium
Phosphate limited cultures of the cyanobacterium Synechococcus are capable of very rapid, opportunistic uptake of phosphate
Author(s) -
Ritchie Raymond J.,
Trautman Donelle A.,
Larkum A. W. D.
Publication year - 2001
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1046/j.0028-646x.2001.00264.x
Subject(s) - phosphate , synechococcus , valinomycin , chemistry , intracellular , phosphorus , biochemistry , environmental chemistry , electrochemical gradient , cyanobacteria , nuclear chemistry , biophysics , biology , membrane potential , bacteria , membrane , organic chemistry , genetics
Summary• Phosphate uptake rates were measured in Synechococcus R‐2 incubated in artificial secondary‐ and tertiary‐treated sewage. • Phosphate uptake was measured using chemical assay and 32 P incorporation. Intracellular pH was measured using accumulation of 14 C‐labelled weak acids and bases and membrane potentials using 86 Rb + /valinomycin. • Synechococcus cells are capable of very rapid, opportunistic uptake of phosphate (10–30 nmol m −2 s −1 ) even though net uptake by growing cultures was < 0.5 nmol m −2 s −1 . Km and Vmax in the light were not significantly different at pH o 7.5 and 10. The mean Km values were 1.91 ± 0.41 mmol m −3 and 0.304 ± 0.055 mmol m −3 for P‐sufficient (secondary‐treated sewage) and P‐deficient (tertiary‐treated sewage) cells, respectively. The transport systems probably recognize both H 2 PO 4 − and HPO 4 2− . Intracellular inorganic phosphate is +28 to +56 kJ mol −1 from electrochemical equilibrium. In P‐sufficient cells uptake is very slow in the dark ( c . 0.1 nmol m −2 s −1 ) but phosphate‐starved cells can opportunistically take up P about 100 times faster. • Two separate ATP‐driven phosphate uptake mechanisms (1 PO 4 in per ATP) appear to be responsible for phosphate uptake by the cells. They have different Km values, different light/dark responses and electrical behaviour.