1微生物細(xì)胞的顯微和亞顯微結(jié)構(gòu)2

1、arrangements of lipids in aqueous mediahydrophobic surfaces such as fatty acyl chains aggregate in aqueous solutions. caused by aversion of water molecules to hydrophobic surfaces which force the water into ordered structures. alternative structures with the hydrophobic surfaces as compact as possib

2、le, are favored.脂質(zhì)體單膜小泡 多膜小泡 雙層體 liposome （脂質(zhì)體）liposome are highly stable structures that can be subjected to manipulations such as gel filtration chromatography and dialysis. with such methods, it is possible to prepare liposome having different inside and outside solution compositions. liposome ca

3、n be used as drug and enzyme delivery systems in therapeutic applications. for example, liposome can be used to introduces contrast agents into the body for diagnostic imaging procedures, including computerized tomographic (ct) and magnetic resonance imaging (mri). liposome can fuse with cells, mixi

4、ng their contents with the intracellular medium. if methods can be developed to target liposomes to selected cell populations, it may be possible to deliver drugs, therapeutic enzymes, and contrast agents to particular kinds of cells (such as cancer cells) （藥物靶）2. protein: 蛋白質(zhì)是組成微生物細(xì)胞膜的另一重蛋白質(zhì)是組成微生物細(xì)

5、胞膜的另一重要成分，可占細(xì)胞膜干重的要成分，可占細(xì)胞膜干重的50-65。按存在的位置分為：按存在的位置分為：鑲嵌蛋白外周蛋白細(xì)菌視紫紅質(zhì) 細(xì)菌視紫紅蛋白（細(xì)菌視紫紅蛋白（bacteriorhodopsin ) 這種蛋白是嗜鹽菌紫膜中所特有的，約占膜重的75%，分子量為26 000da。每分子蛋白上有一分子視黃醛與多肽鏈的一個(gè)賴氨酸結(jié)合在一起，成為具有紫紅色的蛋白質(zhì)。每分子細(xì)菌視紫紅蛋白有7段-螺旋結(jié)構(gòu)組成，每段-螺旋結(jié)構(gòu)長約4nm，橫跨細(xì)胞膜，而使細(xì)胞膜上呈現(xiàn)出六角形格的規(guī)則排列 the 3d structure of bacteriorhodopsin (cross section of t

6、he structural model. selected residues important for proton transfer steps are marked. the probable path of protons is indicated by arrows.the sequence of bacteriorhodopsin written to show the seven transmembrane helices and the extracellular and intracellular loops. the extracellular surface is at

7、the bottom.eiin all these cases, the portion within the lipid bilayer consists primarily of hydrophobic amino acids. these are usually arranged in an alpha helix so that the polar -c=o and -nh groups at the peptide bonds can interact with each other rather than with their hydrophobic surroundings. t

8、hose portions of the polypeptide that project out from the bilayer tend to have a high percentage of hydrophilic amino acids. furthermore, those that project into the aqueous surroundings of the cell are usually glycoproteins, with many hydrophilic sugar residues attached to the part of the polypept

9、ide exposed at the surface of the cell. some transmembrane proteins that span the bilayer several times form a hydrophilic channel through which certain ions and molecules can enter (or leave) the cell.trs130 can be extracted from the p100 fraction by salt, but not by detergent.trs130 is a membrane-

10、associated protein肉豆蔻酰c14異戊二烯基棕櫚酸肉豆蔻酸脂肪族氨基酸糖基磷脂酰肌醇carrier proteins are peripheral proteins which do not extend all the way through the membrane. they move specific molecules through the membrane one at a time. channel proteins extend through the bilipid layer. they form a pore through the membrane t

11、hat can move molecules in several ways. 按照功能分：a. 運(yùn)輸?shù)鞍祝╰ransport proteins） identify the cell/compartment to othersb. marker proteinsmarker proteins extend across the cell membrane and serve to identify the cell. the immune system uses these proteins to tell friendly cells from foreign invaders. they

12、are as unique as fingerprints. c. receptor proteins allow the cell to receive instructionsthese proteins are used in intercellular communication. in this animation you can see a hormone binding to the receptor. this causes the receptor protein release a signal to perform some actiond. enzymes 膜中酶蛋白的

13、種類十分豐富，聚集了關(guān)于細(xì)胞壁、莢膜和細(xì)胞膜膜中酶蛋白的種類十分豐富，聚集了關(guān)于細(xì)胞壁、莢膜和細(xì)胞膜合成的酶類，某些水解酶類如脂酶、蛋白酶和肽酶等，呼吸酶類合成的酶類，某些水解酶類如脂酶、蛋白酶和肽酶等，呼吸酶類和電子傳遞鏈中的各種電子傳遞體，和和電子傳遞鏈中的各種電子傳遞體，和atp酶酶 atp酶酶二、細(xì)胞膜的結(jié)構(gòu)二、細(xì)胞膜的結(jié)構(gòu)流體鑲嵌模型流體鑲嵌模型（fluid mosaic model）膜變窄membrane fluidity: frye-edidin experimentfrye-edidin experimentfrye-edidin experimentmembrane bila

14、yer mobility proteins could move rapidly in biological membranes (frye-edidin experiments)many membrane proteins can move laterally across a membrane at a rate of a few microns per minute. on the other hand, some integral membrane proteins are much more restricted in their lateral movement, with dif

15、fusion rates of about 10nm/sec or even slower. lipids also undergo rapid lateral motion in membrane . a typical phospholipid can diffuse laterally in a membrane at a rate of several um/sec. at that rate, a phospholipid could travel from one end of a bacterial cell to the other in less than a second

16、or traverse a typical animal cell in a few minutes. on the other hand, transverse movement of lipid or protein from one face of bilayer to the other is much slower ( and much less likely) lipid movements in membranesbond rotation (1012 - 1013/sec)translational motion (microns/sec)rotational diffusio

17、n (108 - 109/sec)bilateral motion or flip-flop (days/event)翻轉(zhuǎn)酶翻轉(zhuǎn)酶 ca2+ induce phase separation in membranes formed from phosphatidylserine (ps) 磷脂酰絲氨酸 and phosphatidylethanolamine (pe)磷脂酰乙醇胺 or from ps, pe, and phosphatidylcholine (pc) 磷脂酰膽堿 . ca2+ added to these membranes forms complexes with the n

18、egatively charged serine carboxyl, causing the ps to cluster and separate from the other lipids. such metal-induced lipid phase separation has been shown to regulate the activity of membrane-bound enzymes.membranes are asymmetric structures1. lateral asymmetry （橫向不對稱）（橫向不對稱）membrane lipid asymmetryp

19、cpepssm2. transverse asymmetry （橫向不對稱）（橫向不對稱）(神經(jīng)神經(jīng))鞘磷脂鞘磷脂三、細(xì)胞質(zhì)（三、細(xì)胞質(zhì)（cytoplasm）細(xì)胞質(zhì)無色透明，呈溶膠狀態(tài)，形成結(jié)構(gòu)復(fù)雜的細(xì)胞質(zhì)無色透明，呈溶膠狀態(tài)，形成結(jié)構(gòu)復(fù)雜的三維網(wǎng)狀系統(tǒng)，由細(xì)胞膜伸展至核區(qū)。細(xì)胞質(zhì)的三維網(wǎng)狀系統(tǒng)，由細(xì)胞膜伸展至核區(qū)。細(xì)胞質(zhì)的主要成分為主要成分為水、蛋白質(zhì)、核酸、脂類水、蛋白質(zhì)、核酸、脂類，還有少量，還有少量糖和無機(jī)鹽。由于富含核酸，因而嗜堿性強(qiáng)。幼糖和無機(jī)鹽。由于富含核酸，因而嗜堿性強(qiáng)。幼齡菌細(xì)胞質(zhì)含齡菌細(xì)胞質(zhì)含rnarna多，電子密度較高。老齡菌細(xì)胞多，電子密度較高。老齡菌細(xì)胞質(zhì)的質(zhì)的rna

20、rna含量少，電子密度較低。細(xì)胞質(zhì)中，存在含量少，電子密度較低。細(xì)胞質(zhì)中，存在有單位膜包被的間體和空泡，或僅有單層蛋白質(zhì)有單位膜包被的間體和空泡，或僅有單層蛋白質(zhì)包被的貯存顆粒，如聚包被的貯存顆粒，如聚-羥基丁酸顆粒、糖原羥基丁酸顆粒、糖原顆粒、羧酶體顆粒、羧酶體（carboxsome）和蛋白質(zhì)結(jié)晶等，和蛋白質(zhì)結(jié)晶等，有的根本沒有膜包被。有的根本沒有膜包被。 細(xì)胞質(zhì)的主要功能是：細(xì)胞質(zhì)的主要功能是：為各種細(xì)胞器維持其正常結(jié)構(gòu)及其存在、各種為各種細(xì)胞器維持其正常結(jié)構(gòu)及其存在、各種酶系統(tǒng)及其催化生化反應(yīng)提供所需要的空間、酶系統(tǒng)及其催化生化反應(yīng)提供所需要的空間、理化環(huán)境和一切底物，并容納各生化反應(yīng)的

21、產(chǎn)理化環(huán)境和一切底物，并容納各生化反應(yīng)的產(chǎn)物。一旦由于細(xì)胞膜破裂，細(xì)胞質(zhì)即泄漏或流物。一旦由于細(xì)胞膜破裂，細(xì)胞質(zhì)即泄漏或流失，細(xì)胞必將死亡。失，細(xì)胞必將死亡。四、核糖體（四、核糖體（ribosome） 性狀原核微生物真核微生物小亞單位小亞單位 s值30s40s分子量0.91061.4106rrna s值16s18s堿基數(shù)目15411650蛋白質(zhì) 種類2130分子量范圍8300-258008000-45000大亞單位大亞單位 s值50s60s分子量1.81062.8106rrnas s值5s，23s5s，5.8s，25s堿基數(shù)目120，2904121，158，3360蛋白質(zhì) 種類3245分子量范

22、圍5300-2460011500-45000第二節(jié)第二節(jié) 微生物細(xì)胞的外部結(jié)構(gòu)微生物細(xì)胞的外部結(jié)構(gòu) 一、表面附屬物（一、表面附屬物（surface appendages） （一）、鞭毛、菌毛和性毛（一）、鞭毛、菌毛和性毛 1、細(xì)菌的鞭毛（、細(xì)菌的鞭毛（bacterial flagella） 螺旋菌 detecting bacterial motility since motility is a primary criterion for the diagnosis and identification of bacteria, several techniques have been deve

23、loped to demonstrate bacterial motility, directly or indirectly. 1. flagellar stains outline flagella and show their pattern of distribution. if a bacterium possesses flagella, it is presumed to be motileflagellar stains of three bacteria a. bacillus cereus b. vibrio cholerae c. bacillus brevis (cdc

24、). since the bacterial flagellum is below the resolving power of the light microscope, although bacteria can be seen swimming in a microscope field, the organelles of movement cannot be detected. staining techniques such as leifsons method utilize dyes and other components that precipitate along the

25、 protein filament and hence increase its effective diameter. flagellar distribution is occasionally used to differentiate between morphologically related bacteria. for example, among the gram-negative motile rod-shaped bacteria, the enterics have peritrichous flagella while the pseudomonads have pol

26、ar flagella. 2. motility test medium demonstrates if cells can swim in a semisolid medium. a semisolid medium is inoculated with the bacteria in a straight-line stab with a needle. after incubation, if turbidity (cloudiness) due to bacterial growth can be observed away from the line of the stab, it

27、is evidence that the bacteria were able to swim through the medium. 基體鞭毛絲鞭毛鉤 (a)(a) g g- -細(xì)菌細(xì)菌 （b b）g g+ +細(xì)菌細(xì)菌鞭毛絲（鞭毛絲（filament ）: l成分為成分為鞭毛蛋白（flagellin）l鞭毛亞單位的分子量介于30,000-60,000da之間。l一個(gè)種的鞭毛絲一般由一種鞭毛蛋白亞單位組成，極少有兩種鞭毛蛋白亞單位組成。不同菌種的鞭毛蛋白的氨基酸組成不同，但共同點(diǎn)是都共同點(diǎn)是都不含不含半胱氨酸和色氨酸，脯氨酸、半胱氨酸和色氨酸，脯氨酸、酪氨酸和組氨酸的含量也很低酪氨酸和組氨酸的

28、含量也很低。l鞭毛蛋白具有抗原特異性，稱為h抗原抗原。鞭毛鉤鞭毛鉤（hook）l直徑17nm，長約900nm，約占鞭毛干重的ll是由一種蛋白亞單位組成l蛋白亞單位的分子量因種而異，例如e. coli，salmonella typhimurium的分子量為42 000dal鞭毛鉤蛋白亞單位的氨基酸中，苯丙氨酸和蛋氨酸的含量較高 基體鞭毛絲鞭毛鉤基體基體（basal body）蛋白由蛋白由9-109-10種分子量在種分子量在9,000da-9,000da-60,000da60,000da之之間的多肽鏈間的多肽鏈亞單位裝配亞單位裝配而成。而成。 (a)(a) g g- -細(xì)菌細(xì)菌 b b）g g+

29、+細(xì)菌細(xì)菌（2）功能：）功能：鞭毛是細(xì)菌的運(yùn)動(dòng)器官鞭毛是細(xì)菌的運(yùn)動(dòng)器官運(yùn)動(dòng)時(shí)以運(yùn)動(dòng)時(shí)以m環(huán)為轉(zhuǎn)子帶動(dòng)中軸和鞭毛絲旋轉(zhuǎn)；環(huán)為轉(zhuǎn)子帶動(dòng)中軸和鞭毛絲旋轉(zhuǎn)；s環(huán)、環(huán)、p環(huán)和環(huán)和l環(huán)，起固定軸瓦的作用，允許中軸在其中央環(huán)，起固定軸瓦的作用，允許中軸在其中央孔中旋轉(zhuǎn)。推動(dòng)孔中旋轉(zhuǎn)。推動(dòng)m環(huán)轉(zhuǎn)動(dòng)的環(huán)轉(zhuǎn)動(dòng)的動(dòng)力來自細(xì)胞質(zhì)膜內(nèi)外動(dòng)力來自細(xì)胞質(zhì)膜內(nèi)外的質(zhì)子濃度梯度的質(zhì)子濃度梯度，即膜內(nèi)外的質(zhì)子運(yùn)動(dòng)力，當(dāng)質(zhì)子，即膜內(nèi)外的質(zhì)子運(yùn)動(dòng)力，當(dāng)質(zhì)子自外（或內(nèi)）流向內(nèi)（或外）時(shí)，便推動(dòng)自外（或內(nèi)）流向內(nèi)（或外）時(shí)，便推動(dòng)m環(huán)旋轉(zhuǎn)，環(huán)旋轉(zhuǎn)，每旋轉(zhuǎn)一圈據(jù)推算需要每旋轉(zhuǎn)一圈據(jù)推算需要256個(gè)質(zhì)子。個(gè)質(zhì)子。 two proteins

30、in the flagellar motor, called mota and motb, form a proton channel through the cytoplasmic membrane and rotation of the flagellum is driven by a proton gradient. this driving proton motive force occurs as protons accumulating in the space between the cytoplasmic membrane and the cell wall as a resu

31、lt of the electron transport system travel through the channel back into the bacteriums cytoplasm.the bacterial flagellum can rotate both counterclockwise and clockwise. this is controlled by a protein switch in the molecular motor of the basal body. clockwise rotation results in a tumbling motion a

32、nd changes the direction of bacterial movement. on the other hand, counterclockwise rotation leads to long, straight or curved runs without a change in direction. during a run, that lasts about one second, the bacterium moves 10- 20 times its length before it stops. in the case of a tumble, the move

33、ment lasts only about one-tenth of a second and no real forward progress is made.當(dāng)鞭毛逆時(shí)針轉(zhuǎn)動(dòng)時(shí)，細(xì)菌作直線運(yùn)動(dòng)當(dāng)鞭毛逆時(shí)針轉(zhuǎn)動(dòng)時(shí)，細(xì)菌作直線運(yùn)動(dòng)，順時(shí)針順時(shí)針轉(zhuǎn)動(dòng)時(shí)，細(xì)菌就翻騰轉(zhuǎn)向轉(zhuǎn)動(dòng)時(shí)，細(xì)菌就翻騰轉(zhuǎn)向。這與鞭毛蛋白亞單位鞭毛蛋白亞單位以左手螺旋的方向而成為鞭毛絲有關(guān)以左手螺旋的方向而成為鞭毛絲有關(guān)。鞭毛逆時(shí)針轉(zhuǎn)動(dòng)也是向左轉(zhuǎn)動(dòng)，致使細(xì)菌后部的鞭毛扭成一束，進(jìn)行逆時(shí)針外轉(zhuǎn)動(dòng)，而推動(dòng)細(xì)菌前進(jìn)。當(dāng)鞭毛作順時(shí)針（向右）轉(zhuǎn)動(dòng)時(shí)，鞭毛便散開，而引起翻騰轉(zhuǎn)向。細(xì)菌的趨化性a. 無刺激物時(shí)，e.coli 翻騰時(shí)改變運(yùn)動(dòng)方向a

34、.b. 有刺激物時(shí)，e.coli翻騰時(shí)朝向刺激物濃度較高的方向游動(dòng) b.motility serves to keep bacteria in an optimum environment via taxis. taxis is a motile response to an environmental stimulus. bacteria can respond to chemicals (chemotaxis), light (phototaxis), osmotic pressure (osmotaxis), oxygen (erotaxis), and temperature (the

35、rmotaxis).chemotaxis is a response to a chemical gradient of attractant or a repellent molecules in the bacteriums environment. in an environment that lacks such a gradient, the bacterium moves randomly. it travels in a straight line, or runs, for a few seconds, then stops, tumbles, and runs in a di

36、fferent direction. however, when the bacterium is exposed to a chemical gradient of, for example, an attractant, it tumbles less frequently (has longer runs) as it moves up the gradient, but tumbles at the normal rate if it travels down the gradient. in this way, the net movement is towards a more o

37、ptimum environment.微生物趨化性的機(jī)理微生物趨化性的機(jī)理基粒作為發(fā)動(dòng)機(jī)可驅(qū)動(dòng)鞭毛桿作順時(shí)針和逆時(shí)針方向轉(zhuǎn)動(dòng)。m環(huán)包含flig, mota 和motb 蛋白。用于驅(qū)動(dòng)m環(huán)轉(zhuǎn)動(dòng)的能量來源于mota 和和motb形成形成的通道的通道所產(chǎn)生的質(zhì)子動(dòng)力。motb也起著將m環(huán)固定在細(xì)胞壁中肽聚糖層的作用。 flig 蛋白在接受來自甲基受體趨化蛋白mcps（methyl accepting chemotaxis proteins）的信號后作順時(shí)針或逆時(shí)針方向轉(zhuǎn)動(dòng)。2、細(xì)菌的菌毛（、細(xì)菌的菌毛（fimbriae） 菌毛是廣泛存在于革蘭氏陰性細(xì)菌和某些革蘭菌毛是廣泛存在于革蘭氏陰性細(xì)菌和某些革

38、蘭氏陽性細(xì)菌菌體表面的一層由氏陽性細(xì)菌菌體表面的一層由短且直短且直的氈狀物細(xì)的氈狀物細(xì)絲，原叫絲，原叫繖繖毛（毛（fimbriae），現(xiàn)多稱菌毛（），現(xiàn)多稱菌毛（pili）。 菌毛由菌毛由菌毛蛋白菌毛蛋白組成，菌毛蛋白的氨基酸組成組成，菌毛蛋白的氨基酸組成與鞭毛蛋白的不同。與鞭毛蛋白的不同。 根據(jù)菌毛的形態(tài)和功能，可分為數(shù)個(gè)類型：體根據(jù)菌毛的形態(tài)和功能，可分為數(shù)個(gè)類型：體菌毛、極菌毛和束菌毛等。菌毛、極菌毛和束菌毛等。 超微結(jié)構(gòu)表明菌毛都是由不同數(shù)量的螺旋線超微結(jié)構(gòu)表明菌毛都是由不同數(shù)量的螺旋線空心圓柱體?？招膱A柱體。體菌毛、極菌毛和束菌毛的菌毛蛋白單位數(shù)體菌毛、極菌毛和束菌毛的菌毛蛋白單位數(shù)

39、量、螺旋線和中空圓柱體的內(nèi)外徑各不相同。量、螺旋線和中空圓柱體的內(nèi)外徑各不相同。革蘭氏陰性菌的菌毛著生于細(xì)胞膜，伸出周革蘭氏陰性菌的菌毛著生于細(xì)胞膜，伸出周質(zhì)間隙和細(xì)胞壁。革蘭氏陽性菌的菌毛附著質(zhì)間隙和細(xì)胞壁。革蘭氏陽性菌的菌毛附著于細(xì)胞的位置尚不清楚。菌毛具有較強(qiáng)的再于細(xì)胞的位置尚不清楚。菌毛具有較強(qiáng)的再生能力。生能力。菌毛的功能菌毛的功能并非運(yùn)動(dòng)，而是用于附著基物，也與并非運(yùn)動(dòng)，而是用于附著基物，也與致病性有關(guān)。致病性有關(guān)。致病性細(xì)菌以菌毛粘附到組織細(xì)胞、粘膜細(xì)胞和致病性細(xì)菌以菌毛粘附到組織細(xì)胞、粘膜細(xì)胞和精子細(xì)胞的表面上，這是致病菌侵染宿主的第一精子細(xì)胞的表面上，這是致病菌侵染宿主的第一

40、步。步。l型菌毛還能引起血細(xì)胞凝集作用。但某些細(xì)型菌毛還能引起血細(xì)胞凝集作用。但某些細(xì)菌如不動(dòng)桿菌（菌如不動(dòng)桿菌（acinetobacter）的極菌毛可使細(xì)胞）的極菌毛可使細(xì)胞作顫動(dòng)式運(yùn)動(dòng)。黃色粘球菌的菌毛可引起滑動(dòng)式作顫動(dòng)式運(yùn)動(dòng)。黃色粘球菌的菌毛可引起滑動(dòng)式運(yùn)動(dòng)。運(yùn)動(dòng)。bacteria altering the adhesive tips of their pili3、細(xì)菌的性菌毛（、細(xì)菌的性菌毛（sex pili） 一般認(rèn)為性菌毛也是菌毛的一類，只是由于其較普通菌毛長而粗直長而粗直一些而有別于普通菌毛，而且具有使“雌”、“雄”細(xì)菌接合的功能。性毛的直徑較菌毛的直徑粗，較鞭毛的細(xì)，約為9-1

41、0nm，長而直，數(shù)目少，1-3根。大腸桿菌的性毛分兩型：大腸桿菌的性毛分兩型：一型稱為f pili，長可達(dá)20m。編碼形成f pili的基因位的基因位于于f質(zhì)粒上質(zhì)粒上另一型較短，稱i pili，不超過2m，直徑為7nm。編碼編碼形成形成i plli的基因位于的基因位于col i和和r質(zhì)粒上質(zhì)粒上。f菌毛是由菌毛蛋白單體組成的4條同軸螺旋線，裝配成外徑8nm，內(nèi)徑2nm和螺距為12.8nm的空心圓柱體。f菌毛在內(nèi)膜中裝配，穿過外膜伸展到細(xì)胞表面。構(gòu)成性菌毛的蛋白稱為性菌毛蛋白（pilin）。大腸桿菌性毛蛋白亞單位的分子量為11 800da，含124個(gè)氨基酸，但缺組氨酸、脯氨酸和半胱氨酸。但每分

42、子性菌毛蛋白含有2分子磷酸和1分子葡萄糖。 bacterial species where observedtypical number on celldistribution on cell surfacefunctionescherichia coli (f or sex pilus)1-4uniformmediates dna transfer during conjugationescherichia coli (common pili or type 1 fimbriae)100-200uniformsurface adherence to epithelial cells of t

43、he gi tractneisseria gonorrhoeae100-200uniformsurface adherence to epithelial cells of the urogenital tractstreptococcus pyogenes (fimbriae plus the m-protein)?uniformadherence, resistance to phagocytosis; antigenic variabilitypseudomonas aeruginosa10-20polarsurface adherencesulfolobus acidocaldariu

44、s (an archean)?attachment to sulfur particles4、真核微生物的鞭毛和纖毛、真核微生物的鞭毛和纖毛 某些低等水生真菌和藻類的游動(dòng)孢子以及許多原生動(dòng)物的細(xì)胞表面有鞭毛，單極生或雙極生。有些原生動(dòng)物，如草履蟲細(xì)胞表面著生很多纖毛（cilia）。鞭毛和纖毛都是運(yùn)動(dòng)器官，二者內(nèi)部結(jié)構(gòu)相似，只不過鞭毛長（150m），纖毛短（5-10m），二者直徑相似，約為0.15-0.3m，光學(xué)顯微鏡下，勉強(qiáng)可見。（1）結(jié)構(gòu)）結(jié)構(gòu) 鞭毛和纖毛主要由鞭桿鞭桿（shaft）和基基體體（basal body）兩部分所組成。鞭桿和基體之間有一過渡區(qū)。鞭桿伸出細(xì)胞之外，基體埋于細(xì)胞膜中。

45、鞭桿外有一層單位膜包圍，此膜與細(xì)胞質(zhì)膜相連。鞭桿鞭桿基體基體過渡區(qū)鞭桿的橫切面如圖，中央有一對微管，由中央鞘包著；外圍環(huán)繞有9對二聯(lián)體（doublets）。微管的這種排列，被稱為92型結(jié)構(gòu)型結(jié)構(gòu) 基體又稱生毛體或動(dòng)體，呈短桿狀，在電鏡下觀察，直徑約120-170nm，長為200-500nm，橫切面觀察，可見外圍有9個(gè)三聯(lián)體，中央沒有微管和鞘，為為90型型。 （2）功能）功能真核細(xì)胞的鞭毛或纖毛的功能是運(yùn)動(dòng)，但與細(xì)菌鞭毛的運(yùn)動(dòng)方式完全不同，它們是以波浪形擺動(dòng)波浪形擺動(dòng)（鞭打）（鞭打）以推動(dòng)細(xì)胞前進(jìn)，而不是像細(xì)菌鞭毛那樣轉(zhuǎn)動(dòng)。 （二）、莢膜（二）、莢膜（capsule）和粘液層（）和粘液層（sli

46、me layer） 在形態(tài)上它們可以分為二類： 大莢膜大莢膜（macrocapsules），在光學(xué)顯微鏡下可見，至少0.2m厚，有明確的外界面。 微莢膜微莢膜（microcapsules），厚度小于0.2m，因此在光學(xué)顯微鏡下看不見，但用免疫學(xué)的方法可以測出它們的存在。是否真有微莢膜是有爭論的，有人認(rèn)為組成微莢膜的物質(zhì)是細(xì)胞壁的一種成分； 粘液層粘液層，它積累在微生物細(xì)胞的表面而沒有特定的形態(tài)結(jié)構(gòu)。產(chǎn)生莢膜的微生物也時(shí)常產(chǎn)生粘液層，其組成成分不同于莢膜。在培養(yǎng)液中常會(huì)有組成粘液層的物質(zhì)。1、化學(xué)組成、化學(xué)組成 水是莢膜和粘液層的主要組分，多糖是最常見的莢膜和粘液層的有機(jī)成分。 capsules

47、 are generally composed of polysaccharide; rarely they contain amino sugars or peptides （1）同型多糖（homopolysaccharides） leuconostoc所產(chǎn)生的葡聚糖（glucans）。葡聚糖主要以（16）鍵連接，具有分枝的葡萄糖多聚體，除（16）鍵外，也有些（13）和（14）鍵。它可作為血漿代用品。（2）雜型多糖（heteropolysaccharides）pseudomonas aeruginosa的胞外多糖是由d-葡萄糖，d-半乳糖，d-甘露糖，l-鼠李糖和d-葡萄糖醛酸構(gòu)成的酸性多糖

48、。由于細(xì)菌胞外多糖具有抗原性胞外多糖具有抗原性，因此醫(yī)學(xué)臨床診斷上常用血清學(xué)方法對病原菌進(jìn)行鑒定作快速診斷。（2）雜型多糖（heteropolysaccharides）pseudomonas aeruginosa的胞外多糖是由d-葡萄糖，d-半乳糖，d-甘露糖，l-鼠李糖和d-葡萄糖醛酸構(gòu)成的酸性多糖。由于細(xì)菌胞外多糖具有抗原性胞外多糖具有抗原性，因此醫(yī)學(xué)臨床診斷上常用血清學(xué)方法對病原菌進(jìn)行鑒定作快速診斷。bacteriumcapsule compositionstructural subunitsgram-positive bacteriabacillus anthracispolypept

49、ide (polyglutamic acid)d-glutamic acidbacillus megateriumpolypeptide and polysaccharided-glutamic acid, amino sugars, sugarsstreptococcus mutanspolysaccharide(dextran) glucosestreptococcus pneumoniaepolysaccharidessugars, amino sugars, uronic acidsstreptococcus pyogenespolysaccharide (hyaluronic aci

50、d) n-acetyl-glucosamine and glucuronic acidgram-negative bacteriaacetobacter xylinumpolysaccharide(cellulose) glucoseescherichia colipolysaccharide (colonic acid)glucose, galactose, fucose glucuronic acidpseudomonas aeruginosapolysaccharidemannuronic acidazotobacter vinelandiipolysaccharideglucuroni

51、c acidagrobacterium tumefacienspolysaccharide(glucan) glucose2、功能 碳源和能源貯藏物質(zhì)并能保護(hù)細(xì)胞免受干燥的影響由于能抗宿主吞噬細(xì)胞的吞噬和噬菌體的侵染，增強(qiáng)了某些病原菌的致病能力。例如能引起肺炎的肺炎雙球菌型，如果失去了莢膜，則成為非致病菌。mediate adherence of cells to surfaces. biofilmsome bacteria produce slime materials to adhere and float themselves as colonial masses in their en

52、vironments. other bacteria produce slime materials to attach themselves to a surface or substrate. bacteria may attach to surface, produce slime, divide and produce microcolonies within the slime layer, and construct a biofilm, which becomes an enriched and protected environment for themselves and o

53、ther bacteria. a classic example of biofilm construction in nature is the formation of dental plaque (牙菌斑 ) mediated by the oral bacterium, streptococcus mutans 鏈球菌. （三）、點(diǎn)陣顆粒（三）、點(diǎn)陣顆粒（lattice granule）許多細(xì)菌和一些藍(lán)細(xì)菌（cyanobacteria）都有覆蓋整個(gè)或部分細(xì)胞壁表面的規(guī)則排列的大分子顆粒晶體層，大多數(shù)僅有一層晶體層，也可有兩層重疊但排列不同的晶體層，此稱為點(diǎn)陣顆粒。例如，海洋亞硝化胞囊菌

54、（nitrosocystis oceanus）的兩個(gè)晶體層，分別為六角形和直線形排列。腐蛤螺菌（spirillum putridiconchylium）的細(xì)胞表面，球形顆粒以線狀排列成外層，較大顆粒以四角形排列成內(nèi)層，并以規(guī)則式樣相互聯(lián)合，結(jié)合到細(xì)胞壁脂多糖層凹坑的外表面。 空腸彎曲菌(campylobacter jejuni)表面的點(diǎn)陣顆粒（）負(fù)染(a) 145 000, (b) 175 000（四）、外膜泡（四）、外膜泡（outer membrane vesicle）在掃描電鏡下和負(fù)染標(biāo)本中，均可見到革蘭氏陰革蘭氏陰性性細(xì)菌細(xì)胞表面或周圍，經(jīng)常存在著大小懸殊、形狀多樣的突起物或脫落物。球狀

55、、管狀及其兩者相結(jié)合的復(fù)合體。a. 副百日咳博德特菌(bordetella para pertussis)b. 銅綠假單胞菌（pseudomonas aeruginosa）(a) 大小外膜泡復(fù)合體（*） (b) 增生的多層外膜泡（*）t株霍亂弧菌(vibrio cholerae t-variant)的外膜泡對于外膜泡的形成機(jī)理，wensink（1981）認(rèn)為由于外膜合成速度超過了肽聚糖層的合成速度，外膜便與下面的肽聚糖層局部分離，并向胞外凸出，逐漸膨脹成球狀，或不斷伸長成管狀，或形成兩者的聯(lián)合體。成熟的外膜泡，在基部收縮合攏后便自細(xì)胞上脫落，成為游離的外膜泡 .外膜泡的主要化學(xué)成分是脂多糖化學(xué)

56、成分是脂多糖（lps）。 外膜泡似有防御性作用外膜泡似有防御性作用，細(xì)胞通過釋放外膜泡可擺脫吸附的噬菌體。含有細(xì)菌素（bacteriocin）的外膜泡，能直接抵御噬菌體和其它原核微生物的侵襲。 （五）、螺管結(jié)構(gòu)（螺管結(jié)構(gòu)（coil structure） 個(gè)別細(xì)菌細(xì)胞有一種粗大中空而不易彎曲的菌毛樣個(gè)別細(xì)菌細(xì)胞有一種粗大中空而不易彎曲的菌毛樣附屬物，這種細(xì)絲具有間距附屬物，這種細(xì)絲具有間距12nm、并與垂直線傾斜、并與垂直線傾斜7度的橫向條紋，形成一條螺旋形細(xì)絲，螺旋細(xì)絲外度的橫向條紋，形成一條螺旋形細(xì)絲，螺旋細(xì)絲外覆一個(gè)管狀鞘膜，被稱為螺管結(jié)構(gòu)覆一個(gè)管狀鞘膜，被稱為螺管結(jié)構(gòu) 。黃疸出血型鉤端螺

57、旋體(leptospera icterohaemorrhagiae)的螺管結(jié)構(gòu)(a) 負(fù)染，88,000一段螺線（）從鞘管斷開處（）脫出，失去螺線的這段鞘管變成狹窄（），(b) a圖的高倍放大，負(fù)染 292,000螺管結(jié)構(gòu)起源于細(xì)胞壁，鞘膜由外膜延伸而來，但與細(xì)胞膜之間無結(jié)構(gòu)上的聯(lián)系，這不同于菌毛和鞭毛。螺管結(jié)構(gòu)易自細(xì)胞上脫落和失去鞘膜。有鞘膜的螺管結(jié)構(gòu)直徑6065nm，長13m，基部呈喇叭形。無鞘膜的，呈螺旋線圈狀，直徑3840nm。螺旋線圈易被拉開和壓扁。螺管結(jié)構(gòu)目前僅發(fā)現(xiàn)于鉤端螺旋體屬中，其功能尚不清楚 s-layer：many gram-negative and gram-positi

58、ve bacteria, as well as many archaea possess a regularly structured layer called an s-layer attached to the outermost portion of their cell wall. it is composed of protein or glycoprotein and in electron micrographs, has a pattern resembling floor tiles.characteristic properties of s-layer proteins

59、s-layers are composed of a single protein or glycoprotein species (mw 40-200 kda) and exhibit either oblique, square or hexagonal lattice symmetry with unit cell dimensions in the range of 3 to 30 nm. s-layers are generally 5 to 10 nm thick and show pores of identical size (diameter, 2 - 8 nm) and m

60、orphology. s-layer proteins show a remarkably difference in surface corrugation (皺) and chemistry between inner and outer face. the topography of the inner face (with respect to the bacterial cell) is more corrugated than to outer onefunctions: a. the s-layer may protect bacteria from harmful enzyme