Metabolism of a hybrid algal galactan by members of the human gut microbiome

Craig S Robb, Joanne K Hobbs, Benjamin Pluvinage, Greta Reintjes, Leeann Klassen, Stephanie Monteith, Greta Giljan, Carolyn Amundsen, Chelsea Vickers, Andrew G Hettle, Rory Hills, Nitin, Xiaohui Xing, Tony Montina, Wesley F Zandberg, D Wade Abbott, Alisdair Boraston*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Native porphyran is a hybrid of porphryan and agarose. As a common element of edible seaweed, this algal galactan is a frequent component of the human diet. Bacterial members of the human gut microbiota have acquired polysaccharide utilization loci (PULs) that enable the metabolism of porphyran or agarose. However, the molecular mechanisms that underlie the deconstruction and use of native porphyran remains incompletely defined. Here, we have studied two human gut bacteria, porphyranolytic Bacteroides plebeius and agarolytic Bacteroides uniformis, that target native porphyran. This reveals an exo-based cycle of porphyran depolymerization that incorporates a keystone sulfatase. In both PULs this cycle also works together with a PUL-encoded agarose depolymerizing machinery to synergistically reduce native porphyran to monosaccharides. This provides a framework for understanding the deconstruction of a hybrid algal galactan, and insight into the competitive and/or syntrophic relationship of gut microbiota members that target rare nutrients.

Original languageEnglish
Pages (from-to)501-510
Number of pages10
JournalNature Chemical Biology
Issue number5
Early online date14 Mar 2022
Publication statusPublished - 1 May 2022


  • Bacteria/metabolism
  • Galactans
  • Gastrointestinal Microbiome
  • Humans
  • Polysaccharides/metabolism
  • Sepharose


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