文档介绍：概念:某些细菌生长到一定阶段或在一定环境条件下,细胞的正常生长和分裂停止,细胞内细胞质浓缩,逐步行成一个圆形、椭圆形或圆柱形的,对不良环境有较强抵抗力的特殊结构,称为芽胞。芽胞成熟后可自行从芽胞囊中释放出来。因芽胞的形成都是在细胞内,故又称内生孢子。﹙十﹚芽胞(endospore ,spore) 芽胞芽胞囊 Figure. Gram stain of Bacillus anthracis , the cause of anthrax 1、 Shape,location and relative size to the spore of parent cell 在杆菌中能形成芽孢的种类较多,在球菌和螺旋菌中只有少数菌种可形成芽孢。产生芽孢的几个属: ?(Bacillus) 芽孢杆菌属?(Clostridium) 梭状芽孢杆菌属?(Sporosarcina )芽孢八叠球菌属 2、能形成芽孢的细菌种类芽孢的结构?芽孢的外壁层厚而致密,主要成分为脂蛋白,通透性差,不易着色。?核心含有大量的 DNA 、RNA 、蛋白质酶等物质,还含有 2,6 —吡啶二羧酸(DPA ),DPA 是芽孢特有的成分。一般以 DPA —Ca的形式存在。?皮层主要含芽孢肽聚糖、 DPA —Ca,皮层体积大,比较致密。?芽孢平均含水量低,约40%. 3、芽孢的组成和结构芽孢有多层结构,主要包括孢外壁、芽孢衣、皮层和核心: Figure . Electron micrograph of a bacterial endospore . The spore has a core wall of unique peptidoglycan surrounded by several layers, including the cortex, the spore coat and the exosporium . The dehydrated core contains the bacterial chromosome and a few ribosomes and enzymes to jump-start protein synthesis and metabolism during germination. 轴丝形成形成前芽孢前芽孢隔膜形成前芽孢发育成熟芽孢形成芽孢囊裂解 4、芽孢的形成过程★1、对高温、干燥、辐射、化学药物有强大的抵抗力。★2、含水量低、壁厚而致密,通透性差,不易着色,折光性强。★3、芽胞内新陈代谢几乎停止, 处于休眠状态,但保持潜在萌发力。★4、一个芽孢萌发只产生一个营养状态的细胞。 5、芽孢的特性 Property Vegetative cells Endospores Surface coats Typical Gram-positive murein cell wall polymer Thick spore coat, cortex, and peptidoglycan core wall Microscopic appearance Nonrefractile Refractile Calcium dipicolinic acid Absent Present in core Cytoplasmic water activity High Very low Enzymatic activity Present Absent Macromolecular synthesis Present Absent Heat resistance Low High Resistance to chemicals and acids Low High Radiation resistance Low High Sensitivity to lysozyme Sensitive Resistant Sensitivity to dyes and staining Sensitive Resistant Table. Differences between endospores and vegetative cells