Research Progress in Area 1 方向 ( 一 ) 課題進展 99 Abstract Phytoplankton perform half of the photosynthesis on Earth, forming the basis of the oceanic food web and impacting global biogeochemical cycles, including the nitrogen cycle. Phytoplankton interact with the diverse community of heterotrophic bacteria surrounding them and are preyed upon by viruses. The teams of Dr. Sher and Prof. Zeng are characterizing the phytoplanktonvirus-heterotroph “triangle” of Prochlorococcus, the most abundant phytoplankton clade in the global ocean. We ask how these tri-partite interactions affect the cell structure, elemental stoichiometry and nitrogen budget in laboratory cultures and field samples from the Eastern Mediterranean and South China Sea. Research Activities and Progress • Phage were sent from HKUST to University of Haifa. University of Haifa team has started to work with these phages, including culture infection, collection of supernatant (propagation) and initial experiments to calibrate the experimental conditions; • Macromolecular pools (protein, RNA) and elemental composition (POP) were measured in two Prochlorococcus and to heterotroph strains, under different temperatures; • Preliminary experiments were performed to calibrate methods for measuring refractory C, exudation and polyphosphate. Additionally, methods are being explored to use FTIR to characterize the macromolecular structure; • Preliminary metabolomics results were obtained for phage-infected Prochlorococcus MIT9313. Second experiment is ongoing; • Samples from the HKB research cruise in the South China Sea were analyzed by UH team. Key Findings • Differences in macromolecular structure and resource allocation strategy between phototroph and autotroph strains; • Similar RNA and protein quotas in oligotrophic Eastern Mediterranean and South China Seas. Samples from Pearl River estuary have higher quotas; • Phage infection and lysis dynamics are slower in Prochlorococcus-Alteromonas co-cultures compared with axenic Prochlorococcus. Research Output Publication 0 Trained personnel 3 An Oceanic Triangle: how do the Interactions between Prochlorococcus, Heterotrophic Bacteria and Phage Affect the Cells Molecular Structure, Elemental Stoichiometry and Nitrogen Budget? Dr. Daniel Sher University of Haifa, Israel
RkJQdWJsaXNoZXIy NDk5Njg=