第三章 原核微生物：細(xì)菌和古生菌1

1、A Microbiology Course by Bo CHEN (e-mail: )CONTENTSSurvey of Procaryotic Cell StructureBacterial External StructureBacterial Internal StructureBacterial Shapes, Arrangements, and SizesBacterial Identification and Classification SystemsUnusual Procaryotic GroupsSECTION 1 Survey of Procaryotic Cell St

2、ructure(原核細(xì)胞的結(jié)構(gòu)概覽)Survey of procaryotic cell structure (a typical rod-shaped bacterium). General structure; Special structure10986754123中間體：1.增加表面積；2.類似細(xì)胞器功能糖被儲藏顆粒菌毛性毛鞭毛類核Survey of Procaryotic Cell StructureProcaryotic cell (原核細(xì)胞)Appendages (附體)Cytoplasm (細(xì)胞質(zhì)) Cell envelope (細(xì)胞包被)Flagella (鞭毛) Pili

3、(性毛) Fimbriae (菌毛)Glycocalyx (糖被) Cell wall Cell membraneCell pool Granules (貯藏顆粒) Ribosomes Nucleoid (類核)/chromosomeCapsules (莢膜) Slime layers (粘液層)External structureInternal structureSECTION 2 Bacterial External Structure (細(xì)菌的外部結(jié)構(gòu))2.1 APPENDAGES: CELL EXTENSIONS (附體：細(xì)胞的延伸)Appendages (附體)Flagella (

4、鞭毛) motility (運(yùn)動性)Pili (性毛) DNA transfer (DNA轉(zhuǎn)移)Fimbriae (菌毛) adhesion (粘附)Flagella Bacterial Propellers(鞭毛 細(xì)菌的螺旋槳) 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 (桿菌), and a

5、 small number of cocci (球菌) are flagellatedFig.4.2 Structure of flagella. (a) Electron micrograph of basal bodies and filaments (at arrows) of bacterial flagella (66,000). (b) Details of the basal body in a gram-negative cell.Form of flagella鞭毛絲鞭毛鞘 (sheath)基體!Filament, a helical structure composed o

6、f proteins flagellin (鞭毛絲, 由鞭毛蛋白構(gòu)成), 20 nm in diameter, 1-70 nm in lengthFig.4.3 Electron micrographs depicting types of flagellar arrangementsTypes of flagella (三種類型)1. Monotrichous (a. 單生)2. Lophotrichous (b. 單端叢生) Amphitrichous (c. 兩端叢生)3. Peritrichous (d. 周生)Note: 端生=極生 (polar flagella)Gr. hairy

7、Motility (運(yùn)動性) 運(yùn)動方式不同于鞭子的抽動，而是360旋轉(zhuǎn) (rotation) Velocity: Pseudomonas aeruginosa (銅綠假單胞菌): polar, can swim 4.4 mm/min (2,000-fold the length of the bacterium) E. coli: peritrichous (周生), 1 mm/minFunction of flagellaFig.4.5 The operation of flagella and the mode of locomotion in bacetria with polar an

8、d peritrichous flagella. Direction of rotation:Counterclockwise: swim forward (run) Clockwise: stop (tumble 翻滾)Motility Detectiona. Stab inoculation into a semisolid medium (半固體穿刺培養(yǎng))(a)(b)b. Hanging drop slide (懸滴法)Motile: the cell swims and progresses from one point to another; Nonmotile: the cell

9、oscillates (振蕩) in the same space (Brownian movement).鞭毛與趨向性 They can detect and move in response to chemical and light signals Chemotaxis (趨化性) Positive: favorable chemical stimulus (nutrients, move forward) Negative: harmful chemical stimulus (move away) Phototaxis (趨光性) some photosynthetic bacter

10、iaFig.4.9 Three bacteria in the process of conjugation (bacterial mating 細(xì)菌接合作用).Pili (性毛)Sex pilusFound only on G-bacteriaFunction: DNA TransferFig.4.8 Form and function of bacetrial fimbriaeFunction: adhesion (粘附 attachment)Relationship between Fimbriae and pathogenicity Gonococcus (淋球菌)侵染泌尿道 E. c

11、oli侵染腸道 Mutation and pathogenicityFimbriae (菌毛)(絨毛)2.2 THE CELL ENVELOPE (細(xì)胞包被)123Glycocalyx (糖被) 糖被：是包裹在某些細(xì)菌細(xì)胞壁外的一層膠狀物質(zhì) 多種名稱：多糖-多肽復(fù)合物，糖萼，糖被 兩類： 莢膜 (b)：結(jié)構(gòu)比較緊密，有固定形態(tài)，固定在壁上 粘液層 (a)：結(jié)構(gòu)比較松散，無固定形態(tài)，未固定在壁上不動桿菌屬根瘤菌屬Capsule (莢膜)* the cell proper: the proper cell 嚴(yán)格意義上的(真正的，本身的)細(xì)胞 光滑型菌落：S型，smooth type，mucoid

12、(粘液樣的) ，有莢膜 粗糙型菌落：R型，rough type，noncoid ，無莢膜根據(jù)有無莢膜，菌落分為2種類型：莢膜的功能 保護(hù) (protection)： 極端環(huán)境下（e.g.干旱、貧瘠）防止水分和營養(yǎng)丟失；防止噬菌體的吸附和裂解；防止宿主白細(xì)胞吞噬：有莢膜的肺炎鏈球菌有致病性，引起肺炎，如發(fā)生突變，無莢膜的肺炎鏈球菌致病性大大下降 營養(yǎng)補(bǔ)充 (nutrient supplement)： 莢膜多糖、多肽 粘附 (adhesion)： 定位作用，菌膠團(tuán)（莢膜包裹在細(xì)胞群上，e.g.動膠菌屬Zoogloea）Fig.4.13 Biofilm. Staphylococcus aureus

13、(金葡) cells attached to a catheter (導(dǎo)尿管) by a slime secretion.Application of Capsules 腸膜狀明串株菌 糖被中提取葡聚糖制備“代血漿” 野油菜黃單胞菌 粘液層中提取胞外多糖 黃原膠 新型粘著劑？Cell Wall (細(xì)胞壁) 壁與墻的區(qū)別Cell Wall (細(xì)胞壁) Location: the second layer of cell envelope, between glycocalyx and cell membrane. Composition: mainly composed of peptidogl

14、ycan (肽聚糖), the unique component of eubacteria cell wall (注意：真細(xì)菌特有，古細(xì)菌沒有). Function: keep the cell shape, provide osmotic (滲透壓) protection.1. Glycan chain (聚糖鏈)2. Tetrapeptide side chain (四肽側(cè)鏈)3. Peptide interbridge (肽間橋)(G)(M)Peptidoglycan (肽聚糖)網(wǎng)絡(luò)狀大分子(N-乙酰氨基葡萄糖)(N-乙酰胞壁酸)Glycan chain (聚糖鏈)Lactic aci

15、d糖苷鍵Glycan chain (聚糖鏈) G： N-乙酰氨基葡萄糖 M：N-乙酰胞壁酸 聚糖鏈：每條鏈10-65個(gè)二糖單位 (-G-M-) 金葡：只有9個(gè)二糖單位 地衣芽胞桿菌：79個(gè)二糖單位S.aureus (G+)Peptide chain(G+)=O短肽鏈：包括四肽側(cè)鏈和肽間橋penicillin acting sitePeptide Chain (肽鏈) 四肽側(cè)鏈：4個(gè)aa按L型與D型交替方式連接，在金葡（G+）中為L-Ala-D-Glu-L-Lys-D-Ala，D-型aa在細(xì)菌細(xì)胞壁之外很少出現(xiàn) 肽間橋：金葡中為5個(gè)Gly，不同細(xì)菌可能肽聚糖不同（已知超過100種，肽聚糖多樣性）

16、，主要是肽間橋組成aa不同。 青霉素：作用于肽間橋Gly與四肽側(cè)鏈D-Ala之間（不同抗生素作用效果不同，肽間橋組成多樣性造成，見上圖）Lactic acid糖苷鍵Tetrapeptide side chain (四肽側(cè)鏈,G)N-乙酰胞壁酸乙酰氨基葡萄糖內(nèi)消旋二氨基庚二酸, G-獨(dú)有G四肽側(cè)鏈與G+組成有所不同m-DAP (內(nèi)消旋二氨基庚二酸,G)與Lysine (賴氨酸,G+)Peptidoglycan (肽聚糖)網(wǎng)絡(luò)狀大分子復(fù)合物 由3部分組成：1. Glycan chain (聚糖鏈)2. Tetrapeptide side chain (四肽側(cè)鏈)3. Peptide interbr

17、idge (肽間橋)單層多層: 枯草桿菌20層肽聚糖網(wǎng)狀結(jié)構(gòu)的特點(diǎn) Rigidity 剛性：決定和保持細(xì)胞的形狀 Integrity 完整性：保護(hù)細(xì)胞不致因滲透壓破裂 Meshwork 網(wǎng)狀結(jié)構(gòu)：物質(zhì)交換 (營養(yǎng)吸收、廢物排出)*交聯(lián)度：決定網(wǎng)孔大小與結(jié)構(gòu)強(qiáng)度 (交聯(lián)度越大，網(wǎng)孔越小，結(jié)構(gòu)強(qiáng)度越大)Mechanisms of Antibiotics and Lysozymes(N-乙酰氨基葡萄糖)(N-乙酰胞壁酸)Lysozyme (溶菌酶)糖苷鍵Lysozyme- sensitive bond, lysozyme hydrolyzing sitePenicillin target: binds and blocks peptidaseC=OS.aureus (G+)Penicillin (青霉素)The mode of action of penicillins on the bacterial cell wallPenicillins bind and block peptidases catalyzing the cross-link of glycan molecules, thereby interrupting the completion of the cell wall.“散架”Alexander Fleming (