Polyphosphate Dynamics in Marine Heterotrophic Bacteria Under Phosphorus and Organic Carbon Limitations

Marine heterotrophic bacteria produce polyphosphate (polyP) ubiquitously, yet their polyP functions and ecological significance are rarely studied. We investigated polyP dynamics of three common marine bacteria under phosphorus (P) and organic carbon limitations. Our results show that these bacteria accumulate varying levels of polyP: Alteromonas sp. accumulates up to 87% of polyP in total biomass P, Photobacterium ganghwense accumulates up to 35%, and Vibrio sp. accumulates less than 16%. This variability appears linked to differences in polyP functions. Under P limitation, polyP supports the growth of the two high-polyP-accumulating species, but not in Vibrio sp. with a low polyP level. Under organic carbon limitation, P. ganghwense uniquely degrades polyP for energy and survival. However, this mechanism is not observed under P limitation, despite similar levels of polyP accumulation in the bacteria. The phosphate produced from polyP degradation in P. ganghwense under organic carbon limitation is recycled within cells rather than released into the environment. Overall, our findings suggest that polyP enables some marine heterotrophic bacteria to cope with P and organic carbon limitations, potentially enhancing their competitiveness against phytoplankton for the common limiting nutrient phosphorus in marine ecosystems.