The role of siderophores in algal-bacterial interactions in the marine environment

摘要: Iron is arguably the most important micronutrient in marine environment due to its involvement many vital physiological processes, such as photosynthesis, oxygen transport, electron transfer and nitrogen fixation. However, availability of iron hampered by poor solubility tendency form biologically inaccessible colloidal oxo-polymeric species. This lack more pronounced oceanic where iron(III) even lower than terrestrial environments majority soluble complexed organic ligands that dominate speciation. Consequently, has been shown limit microorganisms large areas ocean. In response limitation, bacteria have produce siderophores, LMW complexing agents possess high affinity for Fe(III). Recently, traditional view siderophores sole chelators challenged discovery their role transport other metals interactions with cell-to-cell communication systems bacteria. Chapters 2 3 this dissertation discuss another unique trait siderophores: ability efficiently bind borate. The concentration boron ocean (0.4 mM) two major siderophore families, catecholates citrates, element suggest a possible unknown biological function. Further proteomic studies are underway examine importance Chapter 4 investigates production group belonging Marinobacter genus, some which were isolated from lab cultures dinoflagellates coccolithophores, limitation. Two algal-associated subclades spp. found photoactive vibrioferrin (VF) while non-algal associated species did not. correlation between algal association VF leads what appears be mutualistic relationship both organisms contribute via photochemistry phytoplankton release dissolved matter (DOM) support growth ultimately fuel biosynthesis VF. influence on speciation further elucidated chapter 5, it ferric- rapidly degrades sunlight leaving behind highly bioavailable iron, Fe'. Because light central consequently any VF-producers phytoplankton, I sought investigate gene expression uptake genes M. algicola DG893. 6 reveals selective related only metabolism addition, environmental samples collected during research cruise North Atlantic 2009 demonstrate VF- producers concentrated near surface daytime. pattern vertical distribution demonstrates although these not abundant ocean, they relevant biogeochemistry work needed elucidate extent contribution