Certain phytoplankton may have a symbiotic association with specific bacterial species driven by a mutualistic sharing of photosynthetically fixed organic carbon and heterotrophic remineralization of limiting nutrients. We proposed the existence of a specific mutualism between vibrioferrin (VF) producing Marinobacter and members of the dinoflagellate and coccolithophore algal lineages. This photolytically active siderophore VF provides an enhanced supply of Fe(III)' to the algae and in return the bacteria would benefit from the release of photosynthate supporting their growth. To provide evidence for this bacterial-algal association we analyzed bacterial community structures with emphasis on the in situ abundance and succession of Marinobacter species inside and outside phytoplankton blooms. Using in situ fluorescence hybridization (FISH) and Marinobacter specific probes we could determine the correlation of certain Marinobacter species with dinoflagellate blooms. Furthermore we detected vibrioferrin biosynthetic genes using quantitative Real-Time PCR (qPCR) and analyzed the importance and abundance of other marine photoreactive siderophores like aerobactin and petrobactin. With this we hope to estimate the potential role of photoreactive siderophores in oceanic iron cycling and their contribution to bacteria-algal mutualism in correlation to phytoplankton blooms.

Role of photoreactive siderophores in algae-bacteria interactions in situ

243rd National Meeting (2012)

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