《细菌的形态与结构》PPT课件.ppt
,细菌的形态与结构,Morphology and structural of bacteria,A general view of bacteria,Bacteria are a group of phylogenetically related prokaryotes including typical bacteria,mycoplasma,chlamydia,rickettsia,spirochetes and actinomyces.Bacteria are small single cell microbes that have to be observed by microscopes.They are present just about everywhere.Some of them are harmful to us,but many of them benefit our life.,The size of bacteria and the significance of being small,Measure of bacterial sizes：m=1/1000mm,细菌体积微小，相对表面积大，有利于其与外界的物质交换。故细菌代谢旺盛，繁殖迅速,=,Surface 4r2,Volume 4/3 r3,=,r,3,Three typical shapes of bacteria,杆菌Bacillus,球菌Coccus,螺形菌Spiral-shaped bacterium,弧菌Vibrio,螺菌Spirillum,螺旋体Spirochete,螺形菌Spiral-shaped bacterium,细菌的结构,细胞膜,细胞壁,核质,细胞质,特殊结构,基本结构,包绕在细胞膜外的一层坚韧有弹性的结构含有肽聚糖(peptidoglycan)维持形态、抵抗低渗、物质交换、具抗原性和染色性革兰氏染色法(Gram Stain)可区分细菌细胞壁差别 革兰氏阳性菌(Gram positive bacteria,G+bacteria)革兰氏阴性菌(Gram negative bacteria,G-bacteria),细胞壁 Cell wall,聚糖骨架(peptidoglycan backbone)：含N-乙酰胞壁酸和N-乙酰葡萄糖胺，两者交替间隔排列，由-1,4 糖苷键相连 四肽侧链(peptide side chain)：与聚糖骨架上N-乙酰胞壁酸相连 五肽交联桥(peptide interbridge)：连接两个相邻的四肽侧链,细胞壁肽聚糖结构,1.肽聚糖含量丰富，层厚，2050层 2.肽聚糖=聚糖骨架+四肽侧链+五肽交联桥=三维立体结构3.含特有组分磷壁酸，此外，某些菌有特殊表面蛋白,革兰氏阳性菌细胞壁特点,(壁)磷壁酸(Teichoic acid),脂(或膜)磷壁酸(Lipoteichoicacid,LTA),如A族链球菌M蛋白金黄色葡萄球菌A蛋白,革兰氏阳性菌细胞壁特殊组分,具抗原性粘附作用,1.肽聚糖含量少，层薄，13层2.肽聚糖=聚糖骨架+四肽侧链=二维平面结构3.肽聚糖层外具有独特的外膜，由脂质双层、脂蛋白 和脂多糖组成，外膜与内膜之间的间隙称周浆间隙,革兰氏阴性菌细胞壁特点,Toxic,anchors in OM,脂多糖=内毒素Lipopolysaccharide(LPS)=Endotoxin,Species or serotype-specific,O antigen,Genus-specific,The cell wall of Gram negative bacteria,OM:Endotoxin：Lipid A gives toxic properties(fever&shock)Negative charge：Protects from phagocytosis OMP：Barrier to some antibioticsO polysaccharides：Serotyping antigensPeriplasm：Rich of enzymesPeptidoglycan：Supporting structure,G-bacteria:functions of cell wall,革兰氏阳性菌与革兰氏阴性菌细胞壁区别,细菌细胞壁缺陷型(Cell wall deficient forms,CWDF;L-form),Derived from normal G+or G-bacteriaInduced by antibiotics,lysozyme,etcDifferent from original cells in many ways:morphology,culture,staining,antigenicity,susceptibility to antibiotics,pathogenicity,etcClinical importance:chronic infection,antibiotic resistance,diagnostic problem,Normalcell,L-form,Penicillin,Lysozyme,Antibacterial mechanismsof lysozyme and penicillin,Transpeptidase,细胞膜 Plasma membrane,细胞质 cytoplasm,Gelatinoid materials surrounded by the plasma membraneIncluding：water,proteins,nucleic acids,lipids,carbohydrates,inorganic salts，etcPlace for cell metabolismImportant inclusions and sub-micro structures:ribosome，plasmid，intracellular granules,核糖体 Ribosome,2 subunits 70s ribosomesProtein synthesisAntibiotics inhibit protein synthesisErythromycin(红霉素)-50SStreptomycin(链霉素)30S,质粒 Plasmid,是细菌染色体外的可独立复制的遗传物质。由闭合的双链环状DNA组成，控制细菌某些特定的遗传性状，非细菌生命活动所必须,医学上重要的质粒（1）F质粒：编码细菌性菌毛（2）R质粒：控制细菌耐药性（3）Col质粒：编码大肠菌素（4）Vi质粒：决定细菌的毒力,胞质颗粒 Intracellular granules：细菌“仓库”,Metachromatic granules(polar body)of Corynebacterium diphtheriae,(RNA+多聚偏磷酸盐，嗜碱性强）,细胞核 Nucleoid,细菌基因组位于单一的共价闭合环状双链DNA分 子上，DNA分子折叠盘旋成松散网状结构，聚集 在细胞质中某一区域，称为拟核(nucleoid)或核质(nuclear material)或细菌染色体(chromosome)无组蛋白成分无核膜包裹,荚膜：包绕在细胞壁外的一层不易着色的粘液性物质化学组成：多糖、少数为多肽(如炭疽芽孢杆菌)功能：抗不良环境：抵抗吞噬细胞吞噬和消化、体液因子的杀菌作用、干燥粘附作用,荚膜 Capsule,鞭毛 Flagella,是细菌细胞表面由蛋白质构成的波状弯曲的、细长的丝状物功能：赋予细菌运动性和趋向性鞭毛有无、鞭毛类型、鞭毛抗原(H抗原)特异性可用于鉴定有助于致病菌定植,菌毛是G-细菌和少数几种G+细菌表 面存在的一种比鞭毛更细、更短、更直的纤丝状蛋白质结构类型 普通菌毛：粘附宿主细胞受体 性菌毛：由F质粒编码，可从F+菌 向F-菌转移，同时可将F+菌部分 染色体DNA带入F-菌(conjugation),菌毛 Pili,fimbriae,是某些G+细菌在一定环境中(特别是营养缺乏时)，在体内形成的圆形或卵圆形不易着色的小体，是细菌的休眠形式有多层膜结构、含水量低、含有独特的吡啶二羧酸抗逆性强(热、干燥、消毒剂、辐射)不是细菌繁殖体，但在适宜条件下可迅速发芽转化为繁殖体细胞,芽胞 Spore,endospore,Clostridium:*产气荚膜梭菌气性坏疽*破伤风梭菌破伤风*肉毒梭菌肉毒中毒Bacillus:*炭疽芽胞杆菌炭疽病*芽胞杆菌彻底灭菌的指标,医学上重要的芽胞产生菌,肽聚糖,抗生素作用靶点,磷壁酸,与细菌粘附宿主细胞有关,吡啶二羧酸,与细菌芽胞的抗逆性有关,LPS,细菌的内毒素,与检验有关的细菌的物理性状：菌体小：用显微镜放大法观察半透明：染色法、相差显微镜、比浊法、分光 光度计法 带负电荷：可与带正电荷的碱性染料结合内部渗透压高：细菌L型培养需高渗培养基,key words,Cell wallPeptidoglycanLTALPS(endotoxin,O antigen)Gram stainGram positive bacteriaGram negative bacteriaL form,Metachromatic granulesPlasmidNucleoidCapsuleFlagela(H antigen)Fimbriae,piliEndosporeAntibiotic targets,
