Figure 1.

Physiological changes of Prochlorococcus MED4 during N deprivation. (a) Effect of N deprivation on cell concentration. (b) Effect of N deprivation on bulk culture fluorescence. (c) Effect of N deprivation on maximum quantum efficiency of photosystem II (Fv/Fm) as measured by fast repetition rate fluorometry. Black lines represent the original triplicate cultures grown in N-replete media; other lines indicate cultures pelleted and resuspended in either N-replete (dark grey line) or N-deficient (light grey line) media. The discontinuity in fluorescence and cell concentration measurements result from incomplete recovery of cells following centrifugation. Error bars represent the standard deviation of three biological replicates and are smaller than the symbols when not visible.