Ligand cross-feeding resolves bacterial vitamin B auxotrophies.

Cobalamin (vitamin B, herein referred to as B) is an essential cofactor for most marine prokaryotes and eukaryotes. Synthesized by a limited number of prokaryotes, its scarcity affects microbial interactions and community dynamics. Here we show that two bacterial B auxotrophs can salvage different B building blocks and cooperate to synthesize B.

The diatom Thalassiosira rotula induces distinct growth responses and colonization patterns of Roseobacteraceae, Flavobacteria and Gammaproteobacteria.

Diatoms as important phytoplankton components interact with and are colonized by heterotrophic bacteria. This colonization has been studied extensively in the past but a distinction between the bacterial colonization directly on diatom cells or on the aggregated organic material, exopolymeric substances (EPS), was little addressed. Here we show that the diatom Thalassiosira rotula and EPS were differently colonized by strains of Roseobacteraceae and Flavobacteriaceae in two and tree partner treatments and an enriched natural bacterial community as inoculum.

Naturally induced biphasic phytoplankton spring bloom reveals rapid and distinct substrate and bacterial community dynamics.

Phytoplankton spring blooms are typical features in coastal seas and provide heterotrophic bacteria with a rich blend of dissolved substrates. However, they are difficult to study in coastal seas in-situ. Here, we induced a phytoplankton spring bloom and followed its fate for 37 days in four 600 L-mesocosms.