上海交通大学：《微生物学 Microbiology》课程教学资源（双语课件）Lecture 3 Microbial Cell Biology（3.3）Cell Wall of Prokaryotes：Peptidoglycan and Related Molecules

上游充通大粤 Shanghai Jiao Tong University Cell Structure and Function Lecture 3-3: Microbial cell biology Zhao Liping,Chen Feng School of Life Science and Biotechnology Shanghai Jiao Tong University http://micro.sjtu.edu.cn

Lecture 3-3: Microbial cell biology Cell Structure and Function Zhao Liping, Chen Feng School of Life Science and Biotechnology Shanghai Jiao Tong University http://micro.sjtu.edu.cn

上充通大学 Shanghai Jiao Tong University 3.8 Cell Wall of Prokaryotes: Peptidoglycan and Related Molecules 原核生物细胞壁：肽聚糖与相关分子

3.8 Cell Wall of Prokaryotes: Peptidoglycan and Related Molecules 原核生物细胞壁: 肽聚糖与相关分子

Lysozyme Wall H2O enters Lysis digests wall Membrane H2O enters H2O enters Lysozyme digests wall Protoplast Protoplasts原生质体 (a)In dilute solution breakdown of the cell wall releases the protoplast,but it immediately lyses because the cytoplasmic membrane is very weak.稀溶液中原生质体会立即破裂

Protoplasts原生质体 (a) In dilute solution breakdown of the cell wall releases the protoplast, but it immediately lyses because the cytoplasmic membrane is very weak. 稀溶液中原生质体会立即破裂

Lysozyme Wall H2O enters Lysis digests wall Membrane H2O enters H2O enters Lysozyme digests wall Protoplast Protoplasts原生质体 (b)In a solution containing an isotonic concentration of a solute such as sucrose,water does not enter the protoplast and it remains stable.等渗溶液中，水不进入原生质体，原生质体稳定

Protoplasts原生质体 (b) In a solution containing an isotonic concentration of a solute such as sucrose, water does not enter the protoplast and it remains stable.等渗溶液中, 水不进入原生质体, 原生质体稳定

h 上浒充通大￥ Shanghai Jiao Tong University What is a cell wall for? A wall is for against pressure-2 atm A wall is for maintaining cell shape A wall is for giving cells rigidity Shanghai Jiao Tong University

Shanghai Jiao Tong University Shanghai Jiao Tong University What is a cell wall for? A wall is for against pressure- 2 atm A wall is for maintaining cell shape A wall is for giving cells rigidity

上海充更大 Shanghai Jiao Tong University Gram stain革兰氏染色 This staining method has long been used for classifying and identifying bacteria (For more detail:Lecture 3-1) Shanghai Jiao Tong University

Shanghai Jiao Tong University Shanghai Jiao Tong University Gram stain革兰氏染色 This staining method has long been used for classifying and identifying bacteria (For more detail: Lecture 3-1)

Step 1 Flood the heat-fixed smear with crystal violet for 1 min 结晶紫染1分钟 All cells purple Step 2 Add iodine solution for 3 min 碘液媒染3分钟 All cells remain purple Steps in the Gram stain procedure.革兰氏染色过程

Steps in the Gram stain procedure.革兰氏染色过程 结晶紫染1分钟 碘液媒染3分钟

Step 3 Decolorize with alcohol briefly -about 20 sec 酒精脱色20秒 Gram-positive cells are purple;gram- negative cells are colorless Step 4 Counterstain with safranin for 1-2 min 沙黄复染1-2分钟 Gram-positive(G+)cells are purple;gram-negative FLASH Gx (G)cells are pink to red

酒精脱色20秒 沙黄复染1-2分钟 FLASH

(⊙ ( Examples of Gram Staining

Examples of Gram Staining

国 Differences in cell wall structure are at the base of differences in the Gram-staining reaction.The G-cell wall is a multilayered structure and quite complex,whereas the G+cell wall consists of primarily a single type of molecule and is often much thicker. Gram-positive Gram-negative Peptidoglycan Peptidoglycan Membrane Membrane Periplasm Lipopolysaccharide and protein Cell walls of Bacteria FLASH

Differences in cell wall structure are at the base of differences in the Gram-staining reaction. The G- cell wall is a multilayered structure and quite complex, whereas the G+ cell wall consists of primarily a single type of molecule and is often much thicker. Cell walls of Bacteria FLASH