Phosphate limited cultures of the cyanobacterium Synechococcus are capable of very rapid, opportunistic uptake of phosphate

Abstract

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 (tertiarytreated 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.

Seasonal and scale-dependent variability in nutrient- and allelopathy-mediated macrophyte–phytoplankton interactions

“…Senescing E. canadensis also may be more susceptible than C. demersum to colonization by microdecomposers (Czeczuga et al, 2005), possibly enhancing nutrient leaching from withering E. canadensis. Favored by its minute size, high CO 2 and P affinity, and adaptive, combined ability to take up inorganic C and N at increasing availability (Ritchie et al, 2001;Tandeau de Marsac et al, 2001), S. leopoliensis may have heavily contributed to the demise of E. canadensis in all but the August flasks (Figure 1). The dramatic d 3 -d 4 recovery by E. canadensis, however, suggests that sprigs were sufficiently healthy or active in August that they were able to successfully counteract S. leopoliensis's initial advantage.…”

Comparative studies on physiological responses to phosphorus in two phenotypes of bloom-forming Microcystis

“…Studies conducted on P uptake in P-limited cyanobacterial cultures revealed that these organisms could increase P i affinity in response to persistent P deficiency. Although P uptake is extremely slow in P-sufficient Synechococcus cells, P-starved cells can opportunistically take up P approximately 100 times faster (Ritchie et al, 2001). Most cyanobacteria can synthesize phosphatase and secrete it into the extracellular space when P i is depleted; this is another important way in which algae enhance P availability by the liberation of P i from dissolved organic P compounds (Mateo et al, 2006;Lee et al, 2005;Whitton et al, 1991).…”

Phosphorus cycling between the colonial cyanobacterium Microcystis aeruginosa and attached bacteria, Pseudomonas

“…In our experiment, there was 25.7 ± 0.31% of 32 P in 32 P-saturated M. aeruginosa released to P-starved bacteria and nearly 50.0% of 32 P in 32 P-saturated bacteria was transferred to P-starved M. aeruginosa, indicating that P-starved cyanobacteria had a significant advantage over bacteria to extract P. Although P uptake is extremely slow in P-sufficient cyanobacterial cells, P-starved cells can opportunistically take up P *100 times faster (Ritchie et al 2001). P-starved cyanobacteria significantly induce phosphate uptake: a 50-fold increase in V max for phosphate transport is observed upon P starvation (Grillo and Gibson 1979).…”