Exudation of dissolved organic carbon by Prochlorococcus

Abstract

Oceanic primary production, the synthesis of organic compounds during photosynthesis by autotrophic bacteria and microalgae, form the base of the marine food web. Pico-cyanobacteria from the Prochlorococcus clade are the most abundant photosynthetic organism in the oceans and therefore play an important role in the production of organic compounds that support the oceanic food web. Prochlorococcus are known to exude multiple DOC compounds, but there is still a lack of knowledge about how Exudation varies between different strains and under different conditions, Such as light intensity and concentrations of nutrients. Understanding under which conditions DOC is excreted and the biochemical composition of the exuded DOC can shed light on oceanic biological and chemical processes such as interactions between autotrophic and heterotrophic microorganisms and the amount of DOC sequestered in seawater. This study is addressing these questions by characterizing and quantifying the exudation of DOC by five Prochlorococcus strains and one Synochococcus strain grown under different culture conditions, and by measuring macromolecular composition of the exudate (carbohydrates, proteins, nucleic acids etc.). In addition, I will try to examine whether the uptake of Prochlorococcus-derived DOC differs between different heterotrophic bacteria.