Xylan Utilization in Human Gut Commensal Bacteria Is Orchestrated by Unique Modular Organization of Polysaccharide-Degrading Enzymes
Xylan utilization in human gut commensal bacteria is orchestrated by unique modular organization of polysaccharide-degrading enzymes Meiling Zhanga,b,c,1,2, Jonathan R. Chekand,1, Dylan Dodda,b,e,1,3, Pei-Ying Hongc,4, Lauren Radlinskia,b,e, Vanessa Revindrana,b, Satish K. Nairb,d,5, Roderick I. Mackiea,b,c,5, and Isaac Canna,b,c,e,5 aEnergy Biosciences Institute, bInstitute for Genomic Biology, and Departments of cAnimal Sciences, dBiochemistry, and eMicrobiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801 Edited by Arnold L. Demain, Drew University, Madison, NJ, and approved July 29, 2014 (received for review April 19, 2014) Enzymes that degrade dietary and host-derived glycans represent One of the most important functional roles specific to the lower the most abundant functional activities encoded by genes unique gut microbiota is the degradation and fermentation of dietary fiber to the human gut microbiome. However, the biochemical activities that is resistant to digestion by human enzymes. The enzymes in- of a vast majority of the glycan-degrading enzymes are poorly volved in breaking down polysaccharides are members of carbo- understood. Here, we use transcriptome sequencing to under- hydrate active enzymes (CAZymes) and are categorized into stand the diversity of genes expressed by the human gut bacteria families of carbohydrate-binding modules (CBMs), carbohydrate Bacteroides intestinalis and Bacteroides ovatus grown in monocul- esterases (CEs), glycoside hydrolases (GHs), glycoside transferases ture with the abundant dietary polysaccharide xylan. The most (GTs), or polysaccharide lyases (PLs) (14). The CAZy gene cat- highly induced carbohydrate active genes encode a unique glycoside alog of the human genome pales in comparison with that of the gut hydrolase (GH) family 10 endoxylanase (BiXyn10A or BACINT_04215 microbiota, which exceeds the total number of human CAZymes and BACOVA_04390) that is highly conserved in the Bacteroidetes by at least 600-fold (15).
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