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1、Medical MicrobiologyChapter 1 IntroductionI. Microbes 1. Definition (microorganism): are the little and simple organisms with rapid growth rates.2. Classification: 1) Noncellular type Such as: virusesGeneral Characteristics of Viruses :1. Smallest: 20 300 nm, most were too small to be seen with the
2、light microscope , filtrable.2. Simplest: non-cellular entity, contain DNA or RNA and protein.3. Obligate intracellular parasites (专性细胞内寄生): growing only within the living cells. 4. Self-replication (自我复制): Once it has invaded a cell it is able to direct the host cell machinery to synthesize new int
3、act infectious virus particles (virions).Definition of a virus:2) Prokaryotic type No nuclear membrane or mitotic apparatus, only nuclear region can be seen, which composed of DNA.No separate internal membrane bound organelles .Such as: Archaebacterium(古细菌): Eubacterium（真细菌）: Bacterium Mycoplusma Ch
4、lamydia Riclcettsia Spirochetes Actinomycetes Cynaobacterium(蓝细菌)：no pathogenesis to human3) Eukaryotic type intracellular membrane enclosed organelles,nucleus : two membrane layers Endoplasmic Reticulum (ER): rough ER ;Smooth ER MitochondriaSuch as Fungi : hyphae and yeast3. Distribution of Microor
5、ganisms:1) In environments.2) In human organismsII Microbiology and Virology1. research objective : Pathogenic Microbes 1)biological properties 2)pathogenesis and immune response 3) Diagnosis 4)therapy and protection Microbiology: Virology：is the study of viruses, complexes of nucleic acids and prot
6、eins that have the capacity for replication in animal, plant and bacterial cells.2. HistoryLeeuwenhock: invent Microscope in 1674 . Pasteur : pasteurization , Vaccine Koch : solid medium, purify bacteria Pathogenic microbe criterion Lister : disinfection aseptic technique Iwanovsky : virus.3. Modern
7、 Microbiology 1) Most bacteria were controled by antibiotics. Drug-resistant strains resistence plasmid. 2) Normal floraopportunistic pathogens (flora disequilibrium super-infection ) Hospital acquired infections. New bacteria : Helicobacter pylorichronic gastritis.3) Viral researches have made prog
8、ress. New presented viruses: AIDSNew diagnostic techniques . ELISA; PCR( polymerase chain reaction.)Viral infection associated with tumors:mechanisms of Viral disease; anti-infection immunology and develop vaccines:Research tools of molecular biology:anti-virus drugs:4) New type vaccine .Microbial g
9、enomic program, MGP .Basic Principles of MicrobiologyChapter 2 Basic Properties of microbesSection I BacteriaI . Size and Shape of bacteria(I ) Size of bacteria Measure unit: um(micrometer): Coccus 1 um bacillus 23um(II) Shape of bacteria 1. coccus (cocci)1) diplococcus : in pairs 2) streptococcus:
10、long chain 3) tetrad and sarcina: 4) staphylococcus: irregular cluster2. bacillus (bacilli): rod3. Spirilla bacterium 1)vihrio v. cholera2)Spirillum Helicobacter H. pyloriII. Basic Bacterial Structure cell wall Basic structure cell membrane, mesosomeCytoplasm: ribosome, plasmid, cytoplasmic granules
11、; nucletid （I）cell wall1. function :1)protection 2) keep the constant shape . 3)antigenicity .4) exchange material2. structure and chemical composition: peptidoglycan（mucopeptide）1)polysaccharide backbone: N-acetyl glucosamine link N-acetyl muramic acid with 1.4 glucosidic bond2)tetrapeptide side ch
12、ain: link muramic acid. ala glu lys ala 3)pentaptide bridge: G+ : Lglycine; G : diaminopimelic acid 3. Special components of Gram-positive cell wall (1) eichoic acids : wall teichoic acid and membrane teichoic acid functions :1) bind Mg2+(magnesium) upply of this ion to the cell2) provide the cell w
13、ith its consistency3) adhesion -pathogenicity 4) antigenicity(2) polysaccharidesmay contain a variety of sugars. 4. Special components of Gram-Negative cell wall .(1) peptidoglycan(2) Outer membrane : exchange receptor(sex pili phaqe)1) Lipoprotein are firmly but non covalently attached to the pepti
14、do-glycan and out membrane 2) lipopolysaccharide, LPS a complex and unique glycolipid consisting of three distinct but covalently linked regions: a) lipid A: glucosamine disaccharide units connected by pyrophosphate bridge . endotoxin , non-genus specificb) core polysaccharidec) specific polysacchar
15、ide “O” Ag（II）Cell membranemesosome : invaginated vesicular membrane，to increase membrane area such as chondriosome(线粒体) and spindle.Function as 1) spindle-like（类纺锤体）：cell division 2) chondroid(类线粒体)：（III）Cytoplasmplasmid：extra-chromosomal genetic material, circle double streands DNA, to replicate i
16、ndependently, to carry genetic information, to control a wide rang of functions to bacteria.（Fertility）factor F -control sex pili factor R-control drug resistance col factor -control E col: to produce bacteriocin.III. Special structure of bacteria Specific structure: capsule, flagellum, pillus, endo
17、spore（I）capsule 1. Concept: bacteria secrete a slime layer outside the cell wall, which is composed of polysacchride or polypeptid.Such as :pneumococcus, anthracis0.2um capsule the rate of reproduction.The living bacteria population decreases with time, due to a lack of nutrients and toxic metabolic
18、 by-products.Section II VirusesI Size and ShapeVirion（病毒体）: The basic infectious particle of a virus is known as the virion.The virion is composed of the nucleic acid genome, structural protein and in some viruses an enclosing lipid-containing envelope. Size : 20 - 300 nm ( the most virus150 nm); Sh
19、ape: the commonest shape - small spherical virus Others-filamentous,brick,bulletII. Structure and Chemical CompositionViruses contain:a nucleic acid genome (RNA or DNA)a protective protein coat (called the capsid)A Viral envelopeNon-structural protein(I) Core : Nucleic acid（核酸） 1. Single kind: consi
20、st of DNA or RNA ( never both).1) DNA :single-stranded DNA (ssDNA):double-stranded DNA ( dsDNA ) : - the commonest type of nucleic acid in viruses of human.2) RNA: double-stranded RNA (dsRNA) :single-stranded RNA (ssRNA): - the commonest type of nucleic acid in viruses of human. ssRNA : is the same
21、as the viral mRNA ,can direct as viral mRNA -ssRNA: as a template transcribe complementary mRNA. Retrovirus: ssRNA2. Functions: 1) virus replication: template2) genome （基因组）: encodes genetic information.3) infectious nucleic acid（感染性核酸）: refer to some viral nucleic acid which can enter cells and rep
22、roduce new viruses,such as dsDNA V and +ssRNA V. *segment of RNA (分节段RNA)*open reading frame, ORF(开放读码框)3. Non-structural protein:(1) viral enzymes: such as： RNA-dependent RNA polymerase or transcriptase .(2) specific viral protein: such as : transformation protein of tumor virus.(II) . Capsid （衣壳）：
23、 protein coat , 1. capsid is composed of distinct morphologic units- capsomeres（壳粒） - icosahedral symmetry: - helical symmetry: - complex symmetry: 2. Functions:1) protection (protect viral nucleic acid from enzymic action).2) specific binding sites.3) antigenicity of capsid protein.(III). Envelope
24、(包膜): lipid, glycoprotein1. Consists of lipid bilayer and glycoprotein:lipid - derived from host cell membrane.Glycoprotein- coded by the viral genome.Spikes(刺突) - virus-encoded glycoprotein protruding from lipid bilayer, which are important for adsorption and entry into the host cell.2. Functions:1
25、) as the binding sites(for enveloped virus).2) antigenicity of glycoprotein.III. Viral MultiplicationReplication: The process of intracellular viral multiplication, consisting of the synthesis of PROTEINS; NUCLEIC ACIDS; and sometimes LIPIDS, and their assembly into a new infectious particle.(I.) Re
26、plication cycle（复制周期）:1. adsorption (吸附): interaction between specific binding sites on viral capsid (or envelope) and specific receptors on host cell surface.2. penetration（穿入）:virus enter the cells.Entry of Naked viruses: endocytosisEntry of enveloped virus :(1) simple fusion of membranes -expels
27、nucleocapsid into cytoplasm (2) entire particle taken up by endocytosis- virus still in vesicle which fuses with endosome (due to low pH)3. uncoating（脱壳）：Rapid change from stable structure to release of genome -depends on virus structure and presence of envelope-during which the endocytic vesicle an
28、d the viral capsid are enzymatically degraded and the viral genome is released. 4. biosynthesis（生物合成）: 4.1 Three kinds of strategies for RNA viruses:(1)Positive-strand viruses a. SYNTHESIS OF VIRAL PROTEINSThe mRNA is translated into a single polypeptide (polyprotein), which is cleaved. Products of
29、cleavage include: An RNA polymerase (replicase)、Structural components of the virion、Proteases .b. RNA REPLICATION1. Viral RNA polymerase copies plus-sense genomic RNA into complementary minus-sense RNA:2. New minus sense strands serve as template for new plus sense strands. 3. New plus strand has th
30、ree alternative fates:i. It may serve as a template for more minus strandsii. It may be packaged into progeny virionsiii. It may be translated into polyprotein (In this case VPg is removed prior to translation)(2) Negative-strand viruses a. TRANSCRIPTIONto refer to synthesis of mRNAs.b. TRANSLATIONMessenger RNAs are translated on host ribosomes and all five viral proteins made at the same time. c. RNA REPLICATIONRNA replication is the process by which new copies of genome-length RNAs are made .RNA replication occurs in the cytoplasm and is carr
