Marine heterotrophic bacteria rely on exogenous organic compounds for their survival and growth. The supply of dissolved organic carbon (DOC) from autotrophs, on the other hand, is controlled by the availability of productivity limiting nutrients, e.g., nitrogen and phosphorus (P). The balance/competition between carbon (C) and nutrient limitations can potentially affect the ecological functions of marine microbial communities. In this talk, we explore the possibility of an intracellular compound, polyphosphate (polyP), in regulating this balance. PolyP is a polymer of phosphate residues linked by high-energy phosphoanhydride bonds, known to be an energy and/or P source for polyP-accumulating organisms. We hypothesize that marine heterotrophic bacteria can cope with the limitation of DOC using dynamic metabolisms of polyP. Using laboratory experiments of pure bacterial culture and natural seawater communities, we show that DOC and inorganic phosphate supply can affect cellular polyP dynamics. PolyP is an energy storage for marine heterotrophic bacteria during C limitation rather than P storage, and the release of phosphate from polyP degradation can support ambient autotrophy.

Primary Presenter: Rixuan GAO, Hong Kong University of Science and Technology (HKUST) (rgaoah@connect.ust.hk)

Authors:

Xingyu YANG, Department of ocean science (HKUST)  (hingjyu@gmail.com)

Jiying LI, Department of ocean science (HKUST); Center for Ocean Research in Hong Kong and Macau  (jiyingli@ust.hk)