土壤拟杆菌与梭菌分解多糖类有机物质的研究进展与展望  

Decomposition of soil polymeric organic matter by Bacteroidetes and Clostridia:progress and perspectives

作　　者：黄俊杰 陆雅海[1] HUANG Junjie;LU Yahai(College of Urban and Environmental Sciences,Peking University,Beijing 100871,China)

机构地区：[1]北京大学城市与环境学院,北京100871

出　　处：《微生物学通报》2022年第3期1147-1157,共11页Microbiology China

基　　金：国家自然科学基金(91951206)。

摘　　要：土壤有机质的分解需要一系列环境微生物的参与,包括上游微生物进行有机质的初步分解、中间微生物的再分解利用和下游微生物的最终代谢过程。由微生物分泌的胞外水解酶将复杂有机质转变为简单有机质是整个分解过程的关键。近年来,针对肠道复杂有机质的微生物分解研究取得了显著进展,本文首先比较了有机质分解过程在人体肠道、反刍动物瘤胃和土壤环境三类生境的异同,然后详细分析比较了拟杆菌门(Bacteroidetes)和梭菌纲(Clostridia)进行糖类物质转运的过程机制。拟杆菌利用T9SS分泌系统进行胞外酶的分泌并依赖其多糖利用位点通过外膜的Sus复合体将初步分解后的寡糖类物质转运至周质空间,周质空间的糖苷水解酶将寡糖类物质进一步分解生成小分子糖,再经由内膜糖转运蛋白转运进胞内完成分解代谢过程。然而梭菌则是依靠纤维小体在胞外进行多聚糖的分解,再被胞外的底物结合蛋白捕获并由ABC转运蛋白转运进胞内,胞内单糖的浓度由双组分系统和碳代谢底物抑制机制协同调控。最后对未来有关土壤有机质分解需要解决的问题进行了展望。The decomposition of soil organic matter requires the coordinated function of microbial guilds,including the preliminary breakdown by upstream microorganisms,the further decomposition by midstream guilds and the final metabolism by downstream organisms.The initial breakdown of complex organic polymers is a key step,which requires the activity of microbial exoenzymes.Significant progress has been achieved recently in the research on the organic matter decomposition in gut.In this review,we compared the organic matter decomposition in human intestine,ruminant rumen and soil,with a focus on the specific mechanisms of polysaccharide transport in Bacteroidetes and Clostridia.Bacteroidetes secrete a cocktail of extracellular hydrolases into the outer membrane via type IX secretion system(T9 SS)and require a series of gene loci termed polysaccharide utilization loci(PUL)to metabolize glycans.Polysaccharides are degraded into oligosaccharides and then transported into the periplasmic space via Sus complex located in the outer membrane.Oligosaccharides are further degraded into simple sugars like glucose and imported into the cell via inner membrane transporter.Clostridia utilize cellulosomes to directly degrade glycans in the extracellular space.The monosaccharides are captured by sugar-binding proteins and transported into the cell via ABC transporters.The intracellular sugar concentration is regulated by two-component systems(TCSs)and carbon catabolite repression(CCR)mechanism.At the end of this review,we put forward the perspectives of the future research on the decomposition of complex organic matter in soil.

关 键 词：有机物质分解 拟杆菌门 多糖利用位点 梭菌纲 ABC转运蛋白 

分 类 号：S154.3[农业科学—土壤学]