医学细胞生物学之细菌的形态与结构.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,第一节 细菌的大小与形态,第二节,细菌的结构,第三节 细菌形态与结构检查法,第1章 细菌的形态与结构,复习题,测量单位：,1.观察细菌常用光学显微镜，其大小用测微尺在显微镜下进行测量，以,微米(m),为测量单位。,2.,不同种类的细菌大小不一:,Baterial cells are usually between 0.4 and 1.5m in short,diameter.,同一种细菌也因菌龄和环境因素的影响而有差异。,细菌按其外形，可分三大类,球菌（,coccus,),杆菌,(bacillus),螺形菌,(spiral bacterium),球菌,杆菌,螺形菌,球菌(coccus),脑膜炎奈瑟菌,双球菌(diplococcus),肺炎链球菌,链球菌,(streptococcus),1500,链球菌扫描电镜图（呈链状）,葡萄球菌扫描电镜图（呈三维）,葡萄球菌(staphylococcus),四联球菌(tetrad,)，,1500,不同杆菌的大小因种类而异,炭疽芽胞杆菌 3-10 m,大,中,大肠埃希菌 2-3 m,小,布鲁菌 0.6-1.5 m,杆菌的形态多样,白喉棒状杆菌,双歧杆菌,霍乱弧菌（,vibrio cholerae,）,鼠咬热螺菌,幽门螺杆菌,基本结构,细胞壁,(cell wall),特殊结构,荚膜,(capsule),细胞膜,(cell membrane),细胞质,(cytoplasm),核质,(nuclear material),鞭毛,(flagellum),芽胞,(spore),菌毛,(pilus/fimbriae),(A),Electron micrograph of a thin section of the Gram-positive,M.lysodeikticus,showing the thick peptidoglycan cell wall(cw),underlying cytoplasmic(plasma)membrane(cm),mesome(m),and nucleoid(n).,(B)Freeze-fractured Bacteriodes cell showing typical major convex fracture faces through the inner(im)and outer(om)membranes.Bars=1 m;circled arrow in Fig.B indicates direction of shadowing.,一、,细胞壁的结构和化学组成,二、,细菌细胞壁缺陷型,（细菌L型）,细 菌,革兰染色,染成紫色或蓝色,染成红色,G+菌,G-菌,细菌细胞壁,革兰阳性菌：,1、肽聚糖：,聚糖骨架、四肽侧链、五肽交联桥,2、磷壁酸,（1）壁磷壁酸,（2）膜磷壁酸（脂磷壁酸）LTA,革兰阴性菌：,1、肽聚糖：,聚糖骨架、四肽侧链,2、外膜,（1）脂蛋白,（2）脂质双层,（3）脂多糖：脂质A,核心多糖,特异多糖,The peptidoglycan layer,Peptidoglycan is a complex polymer consisting of three parts:,a backbone,composed of,a,lternating,N,-,a,c,e,tylgluc,o,s,amine and,N,-acetylmuramic acid;,and a set of identical tetra,p,eptide side chains attached to,N,-acetylmuramic acid;,and a set of identical peptide cross bridges.,聚糖骨架在所有的细菌种类中是相同的,溶菌酶作用位点,四肽侧链和肽交联桥随细菌种类不同而变化,青霉素作用点,例如：革兰阳性菌中的金黄色葡萄球菌,G,-,菌肽聚糖聚糖骨架、四肽侧链,例如：革兰阴性菌中的大肠埃希菌,The fact that all peptidoglycan chains are,cross-linked means that each peptidoglycan,layer is a single giant molecule.,In gram-positive,bacteria,there are as many,as,50 sheets,of peptidoglycan,comprising up to,50%,of the cell wall material;in,gram-negative,bacteria,there appears to be only,one or two,sheets,comprising,510%,of the wall material.,Whose walls are thicker and stronger?,革兰阳性菌细胞壁特殊组分,壁磷壁酸,膜磷壁酸,磷壁酸：,G+菌的重要表面抗原,是某些G+菌的非菌毛黏附素，与致病性有关,Gram-negative cell walls contain three,components that lie outside of the,peptidoglycan layer:,lipoprotein,phospholipid bilayer,and,lipopolysaccharide,.,Outer membrane,脂蛋白,脂质双层：,脂多糖,（lipopolysaccharide,LPS,）,脂质A,(lipid A),核心多糖,(core polysaccharide),特异多糖,（O抗原）,(specic polysaccharide),外膜,OMP,OMP,少数：脂寡糖(LOS),(1)Lipid A,consists of phosphorylated glucosamine disaccharide units to which are attached a number of long-chain fatty acids.,Lipid A is the core structure of LPS.The structure and chemical compositions of lipid A are similar in nearly all Gram-negative bacteria.So the pathophysio,l,ogic effects of LPS(endotoxin)are similar regardless of their bacterial origin.,(3)Each species,however,contains a unique,repeat unit,.,The repeat units are usually linear trisaccharides or branched,tetra-or pentasaccharides.The repeat unit is referred to as,the,O antigen,.,周浆间隙：G-菌有，G+菌没有。含有多种酶。,革兰阴性菌细胞壁,细菌细胞壁的肽聚糖结构受到破坏或合成被抑制，这种细胞壁受损的细菌在,高渗环境下仍可存活者称为细菌细胞壁缺陷型或L型。,蜡样芽胞杆菌L型的镜下形态（多形性）,参考：page 14,图1-7,油煎蛋样菌落,（典型L型菌落）,颗粒型菌落,参考：page 15,图1-8,高渗低琼脂含血清培养基,生长缓慢,典型菌落：荷包蛋样细小菌落,细菌L型临床意义,慢性和反复感染,常规细菌培养为阴性,是否为细菌L型感染？,正使用作用于细,胞壁的药物治疗,做L型的专门培养,更换抗菌药物,细菌细胞膜的结构与真核细胞者基本相同，由,磷脂和多种蛋白质组成，但不含胆固醇（唯一的例外是支原体）,。,The cell membrane.Fragments of the cell membrane(CM)are seen attached to the cell wall(CW)in preparations made from,Escherichia coli.,物质转运,呼吸和分泌：分泌系统（,型）,生物合成：青霉素结合蛋白,(PBP),参与细菌分裂：中介体,(,mesosome,),中介体：是部分细胞膜内陷、折叠、卷曲形成的囊状物，多见于革兰阳性菌。其功能类似于真核细胞的纺锤丝和线粒体。,中介体(mesosome),1.核糖体(ribosome),10-20nm,tens of thousands per cell,2.质粒(plasmid),3.胞质颗粒,/内含物(inclusion),异染颗粒,(metachromatic granule),细胞质（原生质）中的重要结构,为什么作用于核糖体的链霉素和红霉素对人体细胞无影响？,1.质粒(plasmid),是细菌染色体外的遗传物质，存在于细胞质中，为闭合环状的双链DNA，带有遗传信息，控制细菌某些特定的遗传性状。,白喉棒状杆菌的异染颗粒（极体）,细菌不具有成形的核。细菌的遗传物质称为,核质(nuclear material),或,拟核,(nucleoid).,核质由,单一密闭环状DNA分子,反复回旋卷曲盘绕组成松散网状结构,。,about 1mm long,Caption:,Bacterial capsules.Light micrograph of unidentified bacteria(blue)encased in capsules(pink).Each capsule or slime layer(glycocalyx)is a thick layer of slimy material secreted by the bacteria onto their surfaces.They can help the bacteria to attach onto the host cells they are infecting.They may also serve to protect the bacteria from immune cells such as phagocytes.Phase contrast.Magnification:x1000 at 35mm size.,荚膜：厚度0.2m，光镜下可见,微荚膜：厚度,0.2m，,只能通过电镜或,血清学方法检测,粘液层：无固定形状、模糊、,黏液性、胶质,多数为多糖,少数为多肽,血清学分型,荚膜和黏液层含水量95以上,决定细菌的抗原特异性,Demonstration,Direct:Dry-film methods:Staining:Ordinary methods,Special methods,Wet-film methods:Negative staining:India ink,Indirect:Being deduced from serological evidence,Klebsiella pneumoniae,from a pneumonia lung abscess(magnified 1,000).,Bacterial capsules outlined by India ink viewed by light microscopy.,遗传,环境,抗吞噬作用,黏附作用,生物被膜,龋齿,医院内感染,抗有害物质的损伤,荚膜的生物学功能,长520m，直径1230nm,存在于所有的弧菌和螺菌,约半数的杆菌,个别球菌,主要成分：蛋白质,鞭毛抗原（H抗原）,flagellin,鞭毛染色,电镜观察,半固体培养基穿刺接种,观察活菌运动,Demonstration,1.运动(swim),2.有些细菌的,鞭毛与致病性有关,如霍乱弧菌,3.鉴定细菌和,进行细菌分类,趋利避害,鞭 毛 的 功 能,dart,wriggle,tumble,Escherichia coli cells use long,thin structures called flagella to propel themselves.These flagella form bundles that rotate counter-clockwise,creating a torque that causes the bacterium to rotate clockwise.,许多G,-,菌和少数G,+,菌,菌体表面存在的一种比鞭毛更细、更短而直硬的丝状蛋白附属器。,菌毛,鞭毛,菌毛,菌毛由,菌毛蛋白,组成,，具有抗原性。,菌毛必须用电子显微镜观察,。,编码基因位于染色体或质粒上,菌毛按功能分,普通菌毛,和,性菌毛,1.是细菌的粘附结构,2.菌毛的受体常为糖蛋白或糖脂，与菌毛结合的特异性决定了宿主感染的易感部位。,菌毛有不同类型，如型菌毛，型菌毛，定植因子，P菌毛等,与细菌致病性有关,A菌,宿主细胞B,B菌,宿主细胞A,普 通 菌 毛,与细菌的毒力、耐药性等性状的传递有关。,性菌毛：通过接合作用传递遗传物质,Endospores,Some bacteria,notebly those of the genera,Bacillus,and,clostridium,devolope a highly resistant resting phase or endospore,whereby the organism can survive in a dormant state through a long period of starvation or other adverse environmental condition.,The process does not involve multipli,c,ation.,产生芽胞的细菌都是G+菌,是细菌的休眠形式,一个芽胞,一个繁殖体,(vegetative form),遗传,环境,成熟芽胞具有多层膜结构,芽胞带有细菌全部生命必需物质,Differences from vegetative cells:,皮质以及外衣等的不通透性；钙和吡啶二羧酸含量高；含水少；低代谢和低酶活性,肉毒梭菌,破伤风梭菌,炭疽芽胞杆菌,芽胞的大小、形状、位置具有鉴别意义,Demonstration,Unstained.Being recognized by its greater refractivity.,Grams stain.Appearing as a clear space within the stained cell protoplasm.,The spore stain,对热力、干燥、辐射、化学消毒剂等理化,因素均有强大抵抗力,芽胞不直接致病，发芽成繁殖体才能致病,杀灭芽胞最可靠的方法是高压蒸汽灭菌,应以芽胞是否被杀灭作为灭菌效果的指标,芽 胞 的 功 能,观察细菌：,oil-immersion microscopy,大小,形态,排列,鞭毛,芽胞,荚膜,TEM,SEM,涂片、固定,初染-结晶紫,媒染 碘液,脱色95%酒精,复染 复红/沙黄,鉴别细菌、,选择抗菌药物、,研究细菌致病性,复习题,1.,G+菌和G-菌细胞壁的结构和化学组成各有何特点？,举例说明二者结构差异导致哪些后果。,2.何谓细菌L型？简述其形态、染色、培养的主要特点及临床意义。,3.细菌的特殊结构有哪些?各有何主要生物学意义?,4.名词解释：LPS；中介体；质粒；性菌毛；芽胞,5.溶菌酶和青霉素的作用位点。,