医学微生物学第一章 细菌的形态和结构.ppt

Electron Micrograph of Escherichia coli with a Conjugation Pilus F+ Conjugation 4. 芽胞 芽胞是细菌细胞质脱水浓缩，在菌体内形成的圆形或椭圆形的小体，是细菌的休眠形式。 Figure 16. 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. 核心 皮质 芽胞壳 外膜 芽胞外衣 内 外 （1）芽胞的结构 内膜 芽胞壁 （2）形成和发芽 （3）芽胞的特性 1个芽胞体 1个繁殖体 不利条件 条件适宜 不易着色，芽胞染色法 抵抗力强 （1）抵抗力强，灭菌以杀灭芽胞为标准； （2）细菌的鉴别。 （4）意义 三、革兰染色法 结晶紫 碘液 95%酒精 稀释复红 1分，水洗 1分，水洗 30秒，水洗 步 骤 Gram stain of Staphylococcus aureus Gram stain of Escherichia coli G＋菌 紫色 结 果 G—菌 红色 * 常在应用某些抗生素（青霉素、头孢）治疗中发生，且易复发 * Hans Christian Gram was a Danish bacteriologist. He developed the Gram stain as a means to differentiate pneumococci from Klebsiella pneumonia in 1884. It remains one of the most important staining techniques in microbiology today. The Gram stain is often the first test performed in the identification of bacteria.????????? Gram staining is based on the differences in the cell walls of Gram positive and Gram-negative organisms. It is best to use younger cells because older Gram-positive bacteria are subject to break down of the cell wall by enzymes produced by the bacteria with age. Gram-positive organisms have a cell wall composed almost entirely of peptidoglycan whereas Gram-negative organisms have a lipid rich outer wall. This fundamental difference allows the Gram stain to work. The crystal violet complex is an insoluble complex that is difficult to remove. When alcohol is used as a decolorizer, it dehydrates the Gram-positive cell wall and traps the complex inside the cell wall. However, alcohol is able to remove the complex from the lipid rich wall of Gram-negative organisms. The now clear Gram-negative organisms are stained with fuchsin or safranin so that the Gram negative and Gram-positive