医学微生物学课件：1 细菌的形态与结构

1、1 Morphology and Structure of Bacteria2 section 1 Size and Shapes of Bacteria3The bacteria belong to the prokaryote kingdom.Bacteria in size range from about 0.110 mm, often 0.52 mmMicrometer (mm) is usually to be their unit of size.4Basic Shapes and arrangement of the bacteriaCoccus (spherical) Bac

2、illus (rod-like) spiral bacteriumVibrio = curved (弧菌）Campylobacter Spirillum (spiral) （螺菌）Helicobacterium（螺杆菌）Helicobacter5Section 2 The Structure of Bacteria6Basic Components of BacteriaCell wall Cell membrane (cytoplasmic membrane )CytoplasmNucleoid (nuclear material)7Gram positiveGram negativeBac

3、terial structureCell Wall8A single bag-shaped, highly cross-linked macromolecule that surrounds the bacterial cell membrane and provides rigidity. Bacterial structurepeptidoglycan9Glycan (polysaccharide) backbone consisting of N-acetyl muramic acid (Mur) N-acetyl glucosamine (Gln)Peptide side chains

4、 containingD- and L- amino acidsDiaminopimelic acid( DAP二氨基庚二酸, in some cases）The side chains are cross-linked by peptide bridges which vary in structure among bacterial speciespeptide bridgespeptidoglycan10peptidoglycanFor Gram positive bacteriaBackboneSide chainsPeptide bridgesFor Gram negative ba

5、cteriaBackboneSide chains11peptidoglycanPeptidoglycan is a complex, interwoven network that surrounds the entire cell and is composed of a single covalently linked macromolecule. It is found only in bacteria cell walls. It provides rigid support for the cell, is important in maintaining the characte

6、ristic shape of the cell, and allows the cell to withstand media of low osmotic pressure, such as water.Teichoic acid These polymers of glycerol phosphate or ribitol phosphate are located in the outer layer of the gram-positive cell wall. Some of polymers of glycerol teichoic acid penetrate the pept

7、idoglycan layer and are covalently linked to the lipid in the cytoplasmic membrane, in which case they are called lipoteichoic acid; others anchor to the muramic acid of the peptidoglycan. Teichoic acid is antigenic and induces antibodies that are species-specific.a specific component of Gram positi

8、ve bacteria 13Teichoic acidMembrane teichoic acid (lipoteichoic acid) linked to the lipid in the cytoplasmic membraneWall teichoic acidanchor to the muramic acid of the peptidoglycan14teichoic acidFunctions:be antigenic and induces antibodies that are species-specific.AdhesinMaintain the structure o

9、f the cell wallRegulate certain bacterial enzymes 15specific components of Gram positive bacteria the outer membraneLipoproteinLipid bilayerLipopolysaccharide (LPS) 16specific components of Gram negative bacteriaLipopolysaccharide (LPS) (also called endotoxin) which consists of three regions: an out

10、er O antigen (特异性多糖)a middle core （核心多糖）an inner lipid A region （脂质A）displays endotoxin activity17Structure of Lipopolysaccharide18Differences Between Cell Walls of Gram Positive and Negative cell wall Gram Gram thickness 2180nm 1015nm peptidoglycan multilayer single layer Glycan about45% 15%20% lip

11、id 1%4% 1122% teichoic acid yes noOuter membrane no yes 20Functions of the cell wallMaintain the characteristic shapes of the cellAllow the cell to withstand media of low osmotic pressureRefer to the pathogenicity 21Cell wall deficient forms (L forms)Biological featuresMulti-shapesOsmotically protec

12、tive media“fried egg”, 2d7dGram negativeResistant to some antibiotics slow infection 22Bacterial structureTranspeptidase（转肽酶）in cell membranePenicillin targetPenicillin-binding protein23Bacterial structureFive typestype : the most important in G- bacteria蛋白分泌系统24Bacterial structure组氨酸蛋白激酶和反应调节蛋白广泛存在

13、于G+和G-菌中，参与细菌基本活动，与细菌毒力和致病性有关在结构和作用机制上与人类细胞的信号转导系统有本质不同。Two-component signal transduction25Bacterial structureThe cytoplasmic membrane invaginate into the cytoplasmhave a function analogous to the mitochondriaMesosomes26plasmidPlasmids are extrachromosomal, double-stranded, circular DNA molecules th

14、at are capable of replicating independently of the bacterial chromosome. Although plasmids are usually extrachromosomal, they can be integrated into the bacterial chromosome.27Bacterial structureExtrachromosomal, double-stranded, circular DNAusually present in multiple copy numberoften code for path

15、ogenesis and antibiotic resistance factorsreplicate independently of chromosomenot indispensable to the survival of bacteriaplasmids28Important plasmidsfertility plasmid (F plasmid)resistance plasmid (R plasmid) virulence plasmid (Vi plasmid)29Bacterial structureRibosomes 30S 50S the basis of select

16、ive action of several antibiotics that inhibit bacterial,but not human, protein synthesis Cytoplasm of bacteria 70S30Bacterial structureInclusion (storage material)not permanent or essential structures ,may be absent under certain conditions of growthStorage areas of nutrients metachromatic granules

17、 (异染颗粒)Cytoplasm of bacteria31Bacterial structureChromosome A supercoiled double strand DNA No outer nuclear membrane No nucleolus No mitotic spindle No histonesBacterial nucleoid32Specific Components of BacteriaCapsuleFlagellum (pl. Flagella) Pilus (pl. Pili)Spores (or endospores)33CapsulesThe caps

18、ule is a gelatinous layer covering the entire bacterium. It is composed of polysaccharide, except in the anthrax bacillus, which has a capsule of polymerized D-glutamic acid.34CapsulesSurround the outside of the cell envelopeUsually consist of polysaccharide Capsule(0.2mm),microcapsule (0.2mm)Not es

19、sential to cell viability Capsules are often lost during in vitro culture.35CapsulesCapsules of pathogenic bacteriabe protected from phagocytosis adherence to human tissuesTo protect the cell wall against attack by various kinds of antibacterial agents36capsule37flagellaBacteria flagella are thread-

20、like appendages composed entirely of protein, 1230 nm in diameter.The organ of locomotion.Four types of arrangement are known:Monotrichous (单毛菌)Lophotrichous (丛毛菌)Amphitrichous (双毛菌)Peritrichous (周毛菌 )38flagella39Functions of flagellaMotility and taxisPhototaxis (趋光性)Chemotaxis(趋化性)Aerotaxis (趋氧性)Os

21、motaxis(趋渗性)Thermotaxis (趋温性)AntigenicityPathogenicity40Flagellaare long, whiplike appendages that move the bacteria toward nutrients and other attractants. The long filament, which acts as propeller, is composed of many subunits of a single proteins, flagellin, arranged in several intertwined chain

22、s.41Pili (Fimbriae)Pili are hairlike filaments that extend from the cell surface. They are shorter and straighter than flagella and are composed of subunits of a protein, pilin, arranged in helical strands. They are mainly found on gram-negative bacteria.42 Pili are hair-like projections of the cell

23、. The types of pili vary both among and between species. two classes of piliCommon pilus (ordinary pili)adhesion to host epithelial surfaces in infectionSex pilusbe involved in sexual conjugation Pili (fimbriae)43Bacterial spores A specialized structure with enhanced survival value, such as resistan

24、ce to adverse conditions or features that promote dispersion. Spores may result from asexual (e.g., conidia sporangiospores) or sexual reproduction. During sexual reproduction, haploid cells of compatible strains mate through a process of plasmogamy, karyogamy, and meiosis.44Bacterial spores Dormant

25、 form of bacterial cell Produced by certain bacteria when starved The spore is resistant to adverse conditions - high temperature- organic solvents - dryingThe spore contains calcium dipicolinate - dipicolinic acid and calcium （吡啶二羧酸钙）5. Found in the genera Bacillus and Clostridium.45Bacterial spore

26、sSporulation, each vegetative cell forms only one spore Germination, each spore gives rise to a single vegetative cell46Structure of spores4748Functions of spore much more resistant than the vegetative forms. So it can be used to ensure the sterility of products for medical useDistinguish bacteriaSp

27、ores can not cause diseases directly. Only when they become vegetative cells through germination 49The specific components capsule:Anti-phagocytosis, adherenceflagellaThe ability to movepili:adherespores:Strong resistant50Section 3 The physical and chemical properties of bacteria 51Chemical componen

28、tsWater, inorganic salt, protein, sugar, lipid and nucleic acid Physical properties52Section 4 the conditions for growth of bacteria 53The nutritional typesAutotroph: inorganic saltHeterotroph: organic saltNutritional materialsWater, carbon source, nitrogen source, inorganic salt, growth factorsUpta

29、ke of nutritional materialspassive diffusion Active transport54The conditions of bacterial growthNutritional materialspHTemperatureAirosmotic pressure55The conditions of bacterial growthmesophiles (嗜温菌): human body temperature pathogens opportunistspyschrophile (嗜冷菌): close to freezing thermophile (

30、嗜热菌): close to boiling56The conditions of bacterial growthAirObligate aerobe: M. tuberculosisMicroaerophilic bacterium: HpFacultative anaerobe:Obligate anaerobe: C. tetani57 Bacterial requirements for growthtemperature pH osmotic pressuregas requirements58Optimal growth temperature mesophiles (嗜温菌):

31、 human body temperature pathogens opportunistspyschrophile (嗜冷菌): close to freezing thermophile (嗜热菌): close to boiling59Oxygen Requirementsobligate aerobesmust grow in the presence of oxygenthey can not carry out fermentationmicroaerophilic bacteriagrow well in low concentrations of oxygenkilled by

32、 higher concentrations of oxygen60Oxygen Requirementsfacultative anaerobesperform both fermentation and aerobic respirationcan survive in the presence of oxygen61Oxygen Requirementsobligate anaerobesdo not carry out oxidative phosphorylationkilled by O2 lack certain enzymessuperoxide dismutase (超氧化物

33、岐化酶) O2-+2H+ to H2O2 catalase (触酶)(H2O2 to H20 + O2)peroxidase (过氧化物酶)(H2O2 to H20 using NAD to NADH)62Measuring bacterial mass in liquid culturesTurbidity The cloudiness of a liquid culture of bacteria.A measure of total bacteria live and dead.This is usually quantitated with a spectrophotometer.De

34、termination of the number of viable bacteria in a culture.Usually assessed by counting the number of colonies that grow after streaking a known volume on a plate (plate counting of colony forming units). 63Section 5 growth of bacteria 64Bacterial growthBinary fissionA process by which one parent cel

35、l divides to form two progeny cells.Generation time65Generation timetime for bacterial mass to doubleExample 100 bacteria present at time 0 If generation time is 20min After 80min mass = 100 x 24 66Plotting the log of turbidity or number of living cells versus time is referred to as the growth curve

36、. The generation time is the time required for bacterial mass to double.67A decline in the number of viable bacteriaPleomorphism and involutionThe number of new cells produced balances the numberof cells that dieSpore formation, production of exotoxin and antibioticsWhen rapid cell division occursCe

37、lls are sensitive to antibioticsPreparaion of growthThe number of cells appears to remain constantLag phaseExponential phaseStationary phaseDecline phasePhases of growth in a broth culture68Fermentation testsDistinguish bacteria on the basis of fermentation of sugars, such as glucose, maltose, lacto

38、se,the production of pyruvate and lactate turns the medium acidDetected by a pH indicator69Bacterial metabolic products of biosynthesisPyrogen :The substances capable of inducing fever, include endotoxins of gram-negative bacteria and cytokines released from lymphoid cells, such as interleukin-1.Res

39、ist to 121 20min 250 dry heat medicines (Drugs)70Bacterial metabolic products of biosynthesisToxins and enzymesPigments: distinguish bacteriaAntibiotics: polymyxin BBacteriocinvitamins71S epidermidis and S aureus (blood agar plate)72water-solubility pigments of Pseudomonas aeruginosaPyocyanin(绿脓素) f

40、luorescein(荧光素)73Morphological study of bacteria light microscope can magnify 1000 times（0.25m）electron microscopecan resolve 0.001 m particle apartdarkfield microscopefluorescent microscope74Staining methodsGram stainingAcid-fast stainingNegative of background staining75Gram staining76Preparation o

41、f samples smearing dry fix77Gram staincrystal violet iodine 95% alcohol safranin 结晶紫 碘液 95%乙醇 复红 7879microscopyG+: violetG-: red80Significance of Gram stainIdentification of many bacteriaBe helpful to choose of antibioticBe helpful to understand the pathogenicity of a special bacterium81acid-fast st

42、ainDetection of the tubercle bacillus and some other mycobacteriaThe acid-fast bacteria have cell wall with rich lipid content (mainly mycolic acids) and relatively impermeable to simple stains.5% Carbolfuchisn 3% acid alcohol methylene blue823.MicroscopyAcid-fast bacteria83Artificial culture of bac

43、teria84Media for laboratory studiesBasic mediumEnriched mediumSelective mediumDifferential mediumAnaerobic medium85Media for laboratory studies Liquid medium solid medium: bacterial colony （菌落） semi-solid medium86Streaking for Isolation Pure culture A collection of a single type of bacteria isolated and growing free from all other microbes 8788Bacterial classification89Taxonomy of ba