title: Functional metagenomics to mine the human gut microbiome for dietary fiber catabolic enzymes.
abstract: The human gut microbiome is a complex ecosystem composed mainly of uncultured bacteria. It plays an essential role in the catabolism of dietary fibers, the part of plant material in our diet that is not metabolized in the upper digestive tract, because the human genome does not encode adequate carbohydrate active enzymes (CAZymes). We describe a multi-step functionally based approach to guide the in-depth pyrosequencing of specific regions of the human gut metagenome encoding the CAZymes involved in dietary fiber breakdown. High-throughput functional screens were first applied to a library covering 5.4 × 10(9) bp of metagenomic DNA, allowing the isolation of 310 clones showing beta-glucanase, hemicellulase, galactanase, amylase, or pectinase activities. Based on the results of refined secondary screens, sequencing efforts were reduced to 0.84 Mb of nonredundant metagenomic DNA, corresponding to 26 clones that were particularly efficient for the degradation of raw plant polysaccharides. Seventy-three CAZymes from 35 different families were discovered. This corresponds to a fivefold target-gene enrichment compared to random sequencing of the human gut metagenome. Thirty-three of these CAZy encoding genes are highly homologous to prevalent genes found in the gut microbiome of at least 20 individuals for whose metagenomic data are available. Moreover, 18 multigenic clusters encoding complementary enzyme activities for plant cell wall degradation were also identified. Gene taxonomic assignment is consistent with horizontal gene transfer events in dominant gut species and provides new insights into the human gut functional trophic chain.
authors.affiliation: Université de Toulouse, INSA, UPS, INP, LISBP, F-31077 Toulouse, France.
authors.forename: Lena
authors.initials: L
authors.lastname: Tasse
authors.forename: Juliette
authors.initials: J
authors.lastname: Bercovici
authors.forename: Sandra
authors.initials: S
authors.lastname: Pizzut-Serin
authors.forename: Patrick
authors.initials: P
authors.lastname: Robe
authors.forename: Julien
authors.initials: J
authors.lastname: Tap
authors.forename: Christophe
authors.initials: C
authors.lastname: Klopp
authors.forename: Brandi L
authors.initials: BL
authors.lastname: Cantarel
authors.forename: Pedro M
authors.initials: PM
authors.lastname: Coutinho
authors.forename: Bernard
authors.initials: B
authors.lastname: Henrissat
authors.forename: Marion
authors.initials: M
authors.lastname: Leclerc
authors.forename: Joël
authors.initials: J
authors.lastname: Doré
authors.forename: Pierre
authors.initials: P
authors.lastname: Monsan
authors.forename: Magali
authors.initials: M
authors.lastname: Remaud-Simeon
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Potocki-Veronese
mesh_terms: D000328:Adult; D000465:Algorithms; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016000:Cluster Analysis; D019295:Computational Biology / Q000379:methods; D057225:Data Mining / Q000379:methods*; D004043:Dietary Fiber / Q000378:metabolism*; D004798:Enzymes / Q000032:analysis / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D007422:Intestines / Q000382:microbiology*; D008297:Male; D008660:Metabolism / Q000235:genetics; D054892:Metagenome / Q000235:genetics* / Q000502:physiology; D056186:Metagenomics / Q000379:methods*; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D004043:Dietary Fiber; D004798:Enzymes