Evidence for lignin oxidation by the giant panda fecal microbiome.
Evidence for lignin oxidation by the giant panda fecal microbiome.
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DOI：
10.1371/journal.pone.0050312
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Xiao Y
中科院分区：
文献类型：
--
作者：
Fang W;Fang Z;Zhou P;Chang F;Hong Y;Zhang X;Peng H;Xiao Y
大熊猫对竹子中的木质素和木质素相关酚类化合物的消化一直困扰着科学家，因为在以竹子为食的动物的基因组中缺乏木质素降解基因。为了筛选大熊猫粪便中木质素降解菌，构建了大熊猫粪便中木质素降解菌的16 S rRNA基因文库。系统发育分析表明，肠道细菌的主要类群为变形菌门（53%）和厚壁菌门（47%）。两个菌群分别隶属于已知的木质素降解菌恶臭假单胞菌（Pseudomonasputida）和红树林细菌。为了验证大熊猫肠道中的微生物有助于降解木质素的假设，构建了肠道细菌的宏基因组文库，并筛选了含有编码漆酶（木质素降解相关酶）的基因的克隆。从宏基因组克隆中鉴定出一个多铜氧化酶基因，命名为lac 51。序列分析和铜含量测定表明，Lac 51是一种漆酶，而不是金属氧化酶，并可能在其原始宿主细胞外工作，因为它有一个TAT型信号肽和跨膜片段在其N-末端。Lac 51在模拟大熊猫肠道生理环境的条件下氧化多种木质素相关的酚类化合物，包括双羟萘啶、2，6-二甲氧基苯酚、阿魏酸、藜芦醇、愈创木酚和芥子酸。此外，2，2 ′-连氮基-双（3-乙基苯并噻唑啉-6-磺酸）（ABTS）、阿魏酸和胡萝卜酸作为介体，可促进Lac 51对木质素的氧化能力。木质素在445 nm处的吸光度在孵育10 h后分别为ABTS的36%、胡萝卜酸的51%和阿魏酸的51%。我们的研究结果表明，肠道细菌的大熊猫可能会促进木质素部分的氧化，从而阐明了竹木质素的动物消化。
The digestion of lignin and lignin-related phenolic compounds from bamboo by giant pandas has puzzled scientists because of the lack of lignin-degrading genes in the genome of the bamboo-feeding animals. We constructed a 16S rRNA gene library from the microorganisms derived from the giant panda feces to identify the possibility for the presence of potential lignin-degrading bacteria. Phylogenetic analysis showed that the phylotypes of the intestinal bacteria were affiliated with the phyla Proteobacteria (53%) and Firmicutes (47%). Two phylotypes were affiliated with the known lignin-degrading bacterium Pseudomonas putida and the mangrove forest bacteria. To test the hypothesis that microbes in the giant panda gut help degrade lignin, a metagenomic library of the intestinal bacteria was constructed and screened for clones that contained genes encoding laccase, a lignin-degrading related enzyme. A multicopper oxidase gene, designated as lac51, was identified from a metagenomic clone. Sequence analysis and copper content determination indicated that Lac51 is a laccase rather than a metallo-oxidase and may work outside its original host cell because it has a TAT-type signal peptide and a transmembrane segment at its N-terminus. Lac51 oxidizes a variety of lignin-related phenolic compounds, including syringaldazine, 2,6-dimethoxyphenol, ferulic acid, veratryl alcohol, guaiacol, and sinapinic acid at conditions that simulate the physiologic environment in giant panda intestines. Furthermore, in the presence of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), syringic acid, or ferulic acid as mediators, the oxidative ability of Lac51 on lignin was promoted. The absorbance of lignin at 445 nm decreased to 36% for ABTS, 51% for syringic acid, and 51% for ferulic acid after incubation for 10 h. Our findings demonstrate that the intestinal bacteria of giant pandas may facilitate the oxidation of lignin moieties, thereby clarifying the digestion of bamboo lignin by the animal.
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