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Marine Ecology Progress Series

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MEPS - Vol. 461 - Feature article
Scanning electron micrograph of a co-incubation sample containing the diatom Thalassiosira weissflogii (left) and Marinobacter adhaerens HP15 embedded in a network of chitin containing fibres extruding from the diatom cell. Image: Astrid Gärdes

Gärdes A, Ramaye Y, Grossart HP, Passow U, Ullrich MS


Effects of Marinobacter adhaerens HP15 on polymer exudation by Thalassiosira weissflogii at different N:P ratios


Aggregation of phytoplankton cells drives the sinking of organic matter in the ocean. Using a diatom–bacteria model system, Gärdes and co-authors investigated exopolymer production under differing nutrient conditions. The diatom Thalassiosira weissflogii was grown at nutrient-balanced and at nitrogen- or phosphorus-depleted conditions, in the presence or absence of Marinobacter adhaerens. Under nutrient balanced conditions M. adhaerens stimulated both T. weissflogii growth and TEP production. Under nutrient-depleted conditions TEP production was enhanced regardless of whether M. adhaerens was present or not. Differential lectin staining revealed that bacteria enhance and modify the production of those specific extracellular substances. A better understanding of these interactions is crucial to predict consequences of environmental changes on oceanic organic matter and nutrient cycling.


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