第三章原核微生物：细菌和古生菌1讲课.ppt

CONTENTS Survey of Procaryotic Cell Structure Bacterial External Structure Bacterial Internal Structure Bacterial Shapes, Arrangements, and Sizes Bacterial Identification and Classification Systems Unusual Procaryotic Groups SECTION 1 Survey of Procaryotic Cell Structure(原核细胞的结构概览) Survey of Procaryotic Cell Structure SECTION 2 Bacterial External Structure (细菌的外部结构) 2.1 APPENDAGES: CELL EXTENSIONS (附体：细胞的延伸) Flagella — Bacterial Propellers(鞭毛 — 细菌的螺旋桨) Flagellum: Latin, whip 20 nm in diameter, 1-70 nm in length Function: motility, or self-propulsion, to swim in aqueous habitat All spirilla (螺旋菌), about half of the bacilli (杆菌), and a small number of cocci (球菌) are flagellated Motility (运动性) 运动方式不同于鞭子的抽动，而是360°旋转 (rotation) Velocity: Pseudomonas aeruginosa (铜绿假单胞菌): polar, can swim 4.4 mm/min (2,000-fold the length of the bacterium) E. coli: peritrichous (周生), 1 mm/min 鞭毛与趋向性 They can detect and move in response to chemical and light signals Chemotaxis (趋化性) Positive: favorable chemical stimulus (nutrients, move forward) Negative: harmful chemical stimulus (move away) Phototaxis (趋光性) some photosynthetic bacteria 荚膜的功能 保护 (protection)： 极端环境下（e.g.干旱、贫瘠）防止水分和营养丢失；防止噬菌体的吸附和裂解；防止宿主白细胞吞噬：有荚膜的肺炎链球菌有致病性，引起肺炎，如发生突变，无荚膜的肺炎链球菌致病性大大下降 营养补充 (nutrient supplement)： 荚膜多糖、多肽 粘附 (adhesion)： 定位作用，菌胶团（荚膜包裹在细胞群上，e.g.动胶菌属Zoogloea） Application of Capsules 肠膜状明串株菌 糖被中提取葡聚糖制备“代血浆” 野油菜黄单胞菌 粘液层中提取胞外多糖 —黄原胶 新型粘着剂？ Cell Wall (细胞壁) 壁与墙的区别 Cell Wall (细胞壁) Location: the second layer of cell envelope, between glycocalyx and cell membrane. Composition: mainly composed of peptidoglycan (肽聚糖), the unique component of eubacteria cell wall (注意：真细菌特有，古细菌没有). Function: keep the cell shape, provide osmotic (渗透压) protection. Glycan chain (聚糖链) G： N-乙酰氨基葡萄糖 M：N-乙酰胞壁酸 聚糖链：每条链10-65个二糖单位 (…-G-M-…) 金葡：只有9个二糖单位 地衣芽胞杆菌：79个二糖单位 Peptide Chain (肽链) 四肽侧链：4个aa按L型与D型交替方式连接，在金葡（G+）中为L-Ala-D-Glu-L-Lys-D-Ala，D-型aa在细菌细胞壁之外很少出现 肽间桥：金葡中为5个Gly，不同细菌可能肽聚糖不同（已知超过1