Dynamic macromolecular composition and high exudation rates in <i>Prochlorococcus</i>

Every living cell is composed of macromolecules such as proteins, DNA, RNA, and pigments. The ratio between these macromolecular pools depends on the allocation resources within organism to different physiological requirements, in turn affects biogeochemical cycles elements carbon, nitrogen, phosphorus. Here, we present detailed measurements composition Prochlorococcus MIT9312, a representative strain globally abundant marine primary producer, it grows declines due nitrogen starvation laboratory batch cultures. As cells reached stationary stage declined, protein per decreased by ~ 30% whereas RNA pigments 75%. decline was associated with appearance chlorotic cells, which had higher forward scatter (a proxy for size) but lower chlorophyll autofluorescence, well changes photosynthetic pigment composition. Specifically, during culture divinyl-chlorophyll-like emerged, were not observed exponential growth. These also natural samples from Eastern Mediterranean. Over 90% carbon fixed MIT9312 (but strain, NATL2A) released into growth media under conditions. Variations RNA/protein indicate that, broadly defined, more similar eukaryotic phytoplankton than heterotrophic bacteria, possibly significant investment machinery phototrophs.