Bacteria of the human gut microbiome catabolize red seaweed glycans with carbohydrate-active enzyme updates from extrinsic microbes.
Level 5 - mechanism / opinion, no new human data
Bench research, structural biology, and in vitro assays without human clinical data.
PubMed 23150581 · doi:10.1073/pnas.1211002109
What was done
Investigators evaluated a putative polysaccharide utilization locus (PUL) acquired via horizontal gene transfer in the gut bacterium Bacteroides plebeius. They performed transcriptomic profiling and growth assays on the red algal polysaccharide porphyran alongside related substrates (agarose and carrageenan). In addition, they performed biochemical characterization and X-ray crystallography on two PUL-encoded enzymes, BACPLE_01689 and BACPLE_01693.
What was found
The PUL responded to porphyran and enabled B. plebeius growth on porphyran, but not on agarose or carrageenan. X-ray crystallographic and biochemical assays established that BACPLE_01689 and BACPLE_01693 are beta-porphyranases belonging to glycoside hydrolase families GH16 and GH86, respectively. The GH86 product complex structure was resolved at 1.3 A. Specific quantitative growth rates or enzyme kinetic parameters were not reported in the abstract.
Why it matters
This study provides structural and biochemical proof that gut bacteria can acquire functional carbohydrate-active enzymes from marine microbes via horizontal gene transfer to catabolize novel dietary seaweed glycans.
Limits
The study is restricted to in vitro bacterial growth assays, enzyme biochemistry, and crystallographic analysis of a single bacterial strain. No in vivo human intervention or clinical outcome data were evaluated, and quantitative values were omitted from the abstract.
Cited by
- supports Eating sushi provides the human gut with bacteria that facilitate the absorption and digestion of nutrients from seaweed.