第二章 原核微生物形态、构造和功能4(刘).ppt

（四）细菌细胞壁以外的构造 —菌毛(fimbria，复数fimbriae) The capsule has several roles. It protects the cell from DRYING. It serves as an extra source of NUTRITION. in times of need. It helps the cells STICK or attach to things because of its sticky (adhesive) nature and as such is part of biofilms. By sticking the cells to solid surfaces capsules/slime layers prevent them from washing away and provide a protective environment for the cells. It PROTECTS the cell from destruction by white blood cells. It may be TOXIC or inhibitory to a hosts defense system and so aid in the disease process. 应用：荚膜也可以成为有价值的材料。Leucomostoc mesenteroides 的葡聚糖荚膜已用于生产代血浆的主要成分——右旋糖酐和葡聚糖凝胶制剂；从野菜黄单胞菌（Xanthomonas campestris）荚膜提取黄原胶，它是优良的食品添加剂，又是石油开采中优良的压浆剂；用产菌胶团的菌进行污水处理等；通过荚膜的血清学反应进行细菌鉴定（荚膜膨胀试验）。 危害：食品变质发粘；增强致病力；造成严重龋齿等。 Flagella are filamentous protein structures attached to the cell surface that provide the swimming movement for most motile procaryotes. Procaryotic flagella are much thinner than eukaryotic flagella, and they lack the typical 9 + 2 arrangement of microtubules. The diameter of a procaryotic flagellum is about 20 nanometers, well-below the resolving power of the light microscope. The flagellar filament is rotated by a motor apparatus in the plasma membrane allowing the cell to swim in fluid environments. Bacterial flagella are powered by proton motive force (chemiosmotic potential) established on the bacterial membrane, rather than ATP hydrolysis which powers eukaryotic flagella. About half of the bacilli and all of the spiral and curved bacteria are motile by means of flagella. Very few cocci are motile, which reflects their adaptation to dry environments and their lack of hydrodynamic design. 鞭毛（flagellum）：（幻灯片040）细菌体表的细长、波曲的丝状附属物为鞭毛，数目为一到数十根，功能是运动。 检查：电子显微镜直接观察，经鞭毛染色后在光学显微镜下观察，观察暗视野中水浸片或悬滴中运动着的细菌，半固体培养基穿刺接种观察，观察平板菌落形状。构造：阳性菌鞭毛的基体由S、M两个环组成，阴性菌鞭毛的基体由L、P、S、M四个环组成，环中央有鞭毛杆（rod）串插着，鞭毛杆外侧联接一个钩形鞘（hook），其上长有一条长约10~20μm的鞭毛丝（filament）。鞭毛丝一般是由三股鞭毛蛋白链呈螺旋、平行或中间方式紧密结合组成的。幻灯片047.049.050 示细菌鞭毛的基粒构造