Functional metagenomics reveals abundant polysaccharide-degrading gene clusters and cellobiose utilization pathways within gut microbiota of a wood-feeding higher termite

文献类型： 外文期刊

第一作者： Liu, Ning

作者： Liu, Ning;Cao, Lin;Huang, Yongping;Wang, Qian;Liu, Ning;Zhang, Lei;Zhou, Zhihua;Liu, Ning;Li, Hongjie;Currie, Cameron R.;Li, Hongjie;Chevrette, Marc G.;Currie, Cameron R.;Chevrette, Marc G.;Zhou, Haokui;Zhou, Xuguo;Pope, Phillip B.;Wang, Qian

作者机构：

期刊名称：ISME JOURNAL （ 影响因子：10.302； 五年影响因子：12.284 ）

ISSN： 1751-7362

年卷期： 2019 年 13 卷 1 期

页码：

收录情况： SCI

摘要： Plant cell-wall polysaccharides constitute the most abundant but recalcitrant organic carbon source in nature. Microbes residing in the digestive tract of herbivorous bilaterians are particularly efficient at depolymerizing polysaccharides into fermentable sugars and play a significant support role towards their host's lifestyle. Here, we combine large-scale functional screening of fosmid libraries, shotgun sequencing, and biochemical assays to interrogate the gut microbiota of the wood-feeding "higher" termite Globitennes brachycerastes. A number of putative polysaccharide utilization gene clusters were identified with multiple fibrolytic genes. Our large-scale functional screening of 50,000 fosmid clones resulted in 464 clones demonstrating plant polysaccharide-degrading activities, including 267 endoglucanase-, 24 exoglucanase-, 72 beta-glucosidase-, and 101 endoxylanase-positive clones. We sequenced 173 functionally active clones and identified similar to 219 genes encoding putative carbohydrate-active enzymes (CAZymes) targeting cellulose, hemicellulose and pectin. Further analyses revealed that 68 of 154 contigs encode one or more CAZyme, which includes 35 examples of putative saccharolytic operons, suggesting that clustering of CAZymes is common in termite gut microbial inhabitants. Biochemical characterization of a representative xylanase cluster demonstrated that constituent enzymes exhibited complementary physicochemical properties and saccharolytic capabilities. Furthermore, diverse cellobiose-metabolizing enzymes include beta-glucosidases, cellobiose phosphorylases, and phopho-6-beta-glucosidases were identified and functionally verified, indicating that the termite gut micro-ecosystem utilizes diverse metabolic pathways to interconnect hydrolysis and central metabolism. Collectively, these results provide an in-depth view of the adaptation and digestive strategies employed by gut microbiota within this tiny-yet-efficient host-associated ecosystem.

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