An alternative polysaccharide uptake mechanism of marine bacteria

Heterotrophic microbial communities process much of the carbon fixed by phytoplankton in the ocean, thus having a critical role in the global carbon cycle. A major fraction of the phytoplankton-derived substrates are high-molecular-weight (HMW) polysaccharides. For bacterial uptake, these substrates...

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Veröffentlicht in:	The ISME Journal Jg. 11; H. 7; S. 1640 - 1650
Hauptverfasser:	Reintjes, Greta, Arnosti, Carol, Fuchs, Bernhard M, Amann, Rudolf
Format:	Journal Article
Sprache:	Englisch
Veröffentlicht:	London Nature Publishing Group UK 01.07.2017 Oxford University Press Nature Publishing Group
Schlagworte:	14/19 14/32 14/63 631/158/2452 631/158/855 631/326/171/1878 Alteromonadaceae - physiology Atlantic Ocean Bacteria Bacteroidetes - physiology Biological Transport - physiology Biomedical and Life Sciences Carbon cycle Cell culture Communities Cytoplasm Ecology Enzymes Evolutionary Biology Extracellular enzymes Flavobacteriaceae - physiology Fluorescence Fragmentation Fragments Gastrointestinal tract Hydrolysis Illumination Labeling Life Sciences Microbial activity Microbial Ecology Microbial Genetics and Genomics Microbiology Microorganisms Microscopy Oligosaccharides Original original-article Periplasmic space Phytoplankton Plankton Polysaccharides Polysaccharides - metabolism Pure culture Saccharides Seawater - microbiology Staining Substrates
ISSN:	1751-7362, 1751-7370, 1751-7370
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Zusammenfassung:	Heterotrophic microbial communities process much of the carbon fixed by phytoplankton in the ocean, thus having a critical role in the global carbon cycle. A major fraction of the phytoplankton-derived substrates are high-molecular-weight (HMW) polysaccharides. For bacterial uptake, these substrates must initially be hydrolysed to smaller sizes by extracellular enzymes. We investigated polysaccharide hydrolysis by microbial communities during a transect of the Atlantic Ocean, and serendipitously discovered—using super-resolution structured illumination microscopy—that up to 26% of total cells showed uptake of fluorescently labelled polysaccharides (FLA-PS). Fluorescence in situ hybridisation identified these organisms as members of the bacterial phyla Bacteroidetes and Planctomycetes and the gammaproteobacterial genus Catenovulum . Simultaneous membrane staining with nile red indicated that the FLA-PS labelling occurred in the cell but not in the cytoplasm. The dynamics of FLA-PS staining was further investigated in pure culture experiments using Gramella forsetii , a marine member of Bacteroidetes . The staining patterns observed in environmental samples and pure culture tests are consistent with a ‘selfish’ uptake mechanisms of larger oligosaccharides (>600 Da), as demonstrated for gut Bacteroidetes . Ecologically, this alternative polysaccharide uptake mechanism secures substantial quantities of substrate in the periplasmic space, where further processing can occur without diffusive loss. Such a mechanism challenges the paradigm that hydrolysis of HMW substrates inevitably yields low-molecular-weight fragments that are available to the surrounding community and demonstrates the importance of an alternative mechanism of polysaccharide uptake in marine bacteria.
Bibliographie:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 14 content type line 23
ISSN:	1751-7362 1751-7370 1751-7370
DOI:	10.1038/ismej.2017.26