Hyper-specialized Bacteroidetes selfishly compete for laminarin in microalgal blooms

ABSTRACT: Laminarin is a major storage polysaccharide in phytoplankton and an important carbon and energy source for marine microbes. How microbes compete for this labile polysaccharide in nature remains unclear. Here we investigated metaproteomes and metagenomes of bacterioplankton during four consecutive algal blooms in the North Sea to determine key laminarin consumers. We identified two specialized laminarin degraders of the Bacteroidetes group, which reached high abundances year after year. We found that these genomically streamlined bacteria of the genus Formosa have an expanded set of laminarin hydrolases, sensors and transporters that belonged to the most abundant proteins in the blooms. The respective genes are organized in three polysaccharide utilization loci. Proteomic and biochemical analyses revealed surface tethered enzymes and a laminarinase recombined with a membrane-spanning transporter, which act as a disassembly line and efficiently integrate substrate degradation and uptake in the highly diffusive, aquatic environment. We also show that the bloom bacteria couple laminarin utilization with uptake of cellular building blocks such as amino acids. This study suggests that in addition to genome reduction, enzyme fusions, transporter and enzyme expansion also the tight coupling of the carbon and nitrogen uptake make Formosa spp. efficient laminarin utilizers.

INSTRUMENT(S): LTQ Orbitrap Classic

ORGANISM(S): Formosa Sp. Hel1_33_131

TISSUE(S): Cell Culture

SUBMITTER: Frank Unfried  

LAB HEAD: Thomas Schweder

PROVIDER: PXD007934 | Pride | 2018-07-31

REPOSITORIES: Pride