Effects of phosphorus starvation versus limitation on the marine cyanobacterium Prochlorococcus MED4 I: uptake physiology.

Recent measurements of natural populations of the marine cyanobacterium Prochlorococcus indicate this numerically dominant phototroph assimilates phosphorus (P) at significant rates in P-limited oceanic regions. To better understand uptake capabilities of Prochlorococcus under different P stress conditions, uptake kinetic experiments were performed on Prochlorococcus MED4 grown in P-limited chemostats and batch cultures. Our results indicate that MED4 has a small cell-specific Vmax but a high specific affinity (αP ) for P, making it competitive with other marine cyanobacteria at low P concentrations.