Cellulose and hemicellulose decomposition by forest soil bacteria proceeds by the action of structurally variable enzymatic systems.
Cellulose and hemicellulose decomposition by forest soil bacteria proceeds by the action of structurally variable enzymatic systems.
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DOI：
10.1038/srep25279
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发表时间：
2016-04-29
影响因子：
4.6
通讯作者：
Baldrian P
中科院分区：
文献类型：
--
作者：
López-Mondéjar R;Zühlke D;Becher D;Riedel K;Baldrian P
有证据表明，细菌对森林土壤中纤维素和半纤维素的分解起积极作用；然而，它们在这一过程中的作用尚不清楚。在此，我们对温带栎林凋落物和有机土壤中具有潜在纤维素降解活性的细菌进行了筛选和鉴定。研究人员对该生态系统中丰富的三种纤维素水解菌进行了基因组测序，并对其在植物生物量和微晶纤维素上生长过程中的蛋白质组进行了表征。Pedobacter和Mucilaginibacter表现出复杂的酶系统，其中含有多种降解纤维素和半纤维素的糖活性酶，这些酶在功能上对内切葡聚糖酶、β-葡萄糖苷酶、内切木聚糖酶、β-木糖糖苷酶、甘露糖糖苷酶和糖结合模块是冗余的。Luteibacter不表达任何传统上被认为是纤维素酶的糖基水解酶。相反，纤维素分解可能是由含有纤维素结合结构域的表达的GH23家族蛋白进行的。有趣的是，植物木质纤维素和结晶纤维素的存在都会引发一系列水解蛋白的产生，包括纤维素酶、半纤维素酶和其他糖基水解酶。我们的发现强调了纤维素分解土壤细菌中酶系统的广泛和未被探索的结构多样性，并表明了多种丰富的细菌分类群在纤维素和其他植物多糖分解中的作用。
Evidence shows that bacteria contribute actively to the decomposition of cellulose and hemicellulose in forest soil; however, their role in this process is still unclear. Here we performed the screening and identification of bacteria showing potential cellulolytic activity from litter and organic soil of a temperate oak forest. The genomes of three cellulolytic isolates previously described as abundant in this ecosystem were sequenced and their proteomes were characterized during the growth on plant biomass and on microcrystalline cellulose. Pedobacter and Mucilaginibacter showed complex enzymatic systems containing highly diverse carbohydrate-active enzymes for the degradation of cellulose and hemicellulose, which were functionally redundant for endoglucanases, β-glucosidases, endoxylanases, β-xylosidases, mannosidases and carbohydrate-binding modules. Luteibacter did not express any glycosyl hydrolases traditionally recognized as cellulases. Instead, cellulose decomposition was likely performed by an expressed GH23 family protein containing a cellulose-binding domain. Interestingly, the presence of plant lignocellulose as well as crystalline cellulose both trigger the production of a wide set of hydrolytic proteins including cellulases, hemicellulases and other glycosyl hydrolases. Our findings highlight the extensive and unexplored structural diversity of enzymatic systems in cellulolytic soil bacteria and indicate the roles of multiple abundant bacterial taxa in the decomposition of cellulose and other plant polysaccharides.