粘细菌纤维堆囊菌降解纤维素多酶复合体的确证和性质分析

【作者】 侯配斌；

【导师】 李越中；

【作者基本信息】 山东大学 ， 微生物学， 2006， 博士

【摘要】 粘细菌是一类特殊的革兰氏阴性杆菌，能够进行滑行运动，具有复杂的多细胞行为和形态发生过程，是一类“生活在真核生物边缘”的高等的原核生物类群；产生众多结构新颖、作用机制独特的生物活性次级代谢产物是粘细菌的另一重要特征。根据“食性"的差异可将粘细菌简单的划分为溶细菌和溶纤维素两个生理类群。溶纤维素群中只有堆囊菌属一个属，纤维堆囊菌是其中的模式种。作为重要的微生物药物(例如著名的埃博霉素)产生菌，纤维堆囊菌逐渐引起全球的广泛关注。但是，对其最为基本的微生物学特性——粘细菌中唯一能够降解纤维素、半纤维素等生物大分子的类群，相关研究则涉及很少。本文利用实验室所建立的国内最大的粘细菌资源库的优势，对纤维堆囊菌降解纤维素的基本性质及相关酶类进行了研究。 纤维素是地球上最丰富的可再生有机资源，对纤维素的降解基本上是由微生物完成的。不同微生物降解纤维素时所采取的策略也不尽相同，主要表现在各种降解酶类的作用机制和组织形式上。纤维堆囊菌能够在以纤维素为唯一碳源的简单无机盐培养基(如CNST培养基)上生长，可产生多种纤维素和半纤维素酶类。所以，我们从表征其纤维素酶类的基本性质出发，开展了相关研究。广泛选取了13株纤维堆囊菌作为研究对象，对其在不同纤维素底物上的生长形态、降解纤维素特征、分化发育能力以及多种纤维素和半纤维素酶类的产生时间进行了测定和比较。通过对各菌株在滤纸纤维素底物上生长和子实体形成情况的分析，我们将其总结为两种不同的类型：一种类型是以接种点为中心，先向四周快速扩展，在扩展过程中伴随着滤纸纤维素的降解，达到一定程度以后，整个菌落的细胞同时开始聚集，并形成子实体结构，其子实体基本在生长同一时期形成，并布满整个菌落，这种类型的特点就是几乎所有的菌体细胞都处于相同的生长时期，细胞生长和分化发育具有一定的同步性；另一种类型是在菌落外围菌体细胞仍在增殖扩展时，靠近中心部位的菌体则已开始聚集和进入分化发育阶段，首先形成子实体结构，随着培养时间的延长，外围细胞也逐渐形成子实体结构，其子实体最终布满菌落中心部位或整个菌落，这种类型的特点就是菌落中不同部位的细胞所处更多还原

【Abstract】 The myxobacteria are a special kind of Gram-negative unicellular bacteria with rod-shaped vegetative cells. Because of their gliding movement, complicated multicellular behavior and morphogenesis process, the myxobacteria are generally considered as advanced prokaryotes, which may live on the edge of eukaryotes. Another outstanding trait of the myxobacteria is that they can produce a large number of bioactive secondary metabolites with some novel structures and unique mechanism of action. Based on their specialization in degradation of biomacromolecules, they are divided into two groups, one is bacteriolytic, and the other is cellulolytic. Within cellulolytic group, there is only one genus named Sorangium, in which Sorangium cellulosum is the type species in this genus. As an important medicine microbial producer (e.g. the famous antitumor drug epothilone), S. cellulosum draws worldwide attention. However, very few studies have been focused on the activity of degrading biomacromolecular materials, such as cellulose and hemicellulose, which is the unique and basic property of S. cellulosum among the myxobacteria. In virtue of the biggest domestic myxobacteria strain bank established by our laboratory, this paper tried to explore the characteristics and mechanism of Sorangium’s cellulolytic activity.Cellulose is the most abundant and renewable organic biopolymer on earth and the degradation of cellulose is mainly carried out by microorganisms. Different microorganisms select different strategies to hydrolyze cellulose, represented by the organization and mechanism of action of their cellulolytic enzymes. Sorangium strains can grow on simple inorganic salt medium (e.g. CNST medium) with cellulose as the only carbon source by producing cellulases and hemicellulases. Accordingly, to elucidate basic property of cellulases produced by S. cellulosum was set as our research starting point. The morphologies, cellulolytic characteristics and更多还原