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1、Introduction of Microbiology, Bacterial Structure Pin Lin (凌 斌), Ph.D. Departg ment of Microbiology 6th edition) 2. 醫用微生物學 (商惠芳 審閱, 6th edition) 課程要點 (Outline)Introduction of Medical MicrobiologyBacterial ClassificationBacterial StructureHistory of Microbiology1.In 1674 Dutuch biologist Leeuwenhoek
2、discovered a world of tiny “animalcules” (microbes) by microscope. 2.In 1840 German Pathologist Friedrich Henle proposed “Germ Theory” for proving microorganisms causing diseases. 3. Robert Koch grapelike clusters, diplococcus; two cells together Rod-shaped bacterium: Bacillus Escherichia coli : bac
3、illus. Spirillum: Snakelike treponeme some bacteria (螺旋菌屬) 原核細胞 (Prokaryote)的特徵真核細胞 (Eukaryote)的特徵EukaryoteProkaryoteMajor groupsFungi, plants, animalsbacteriaSize 5 m0.5-3.0 mNuclear structures NucleusChromosomesClassic membraneStrands of DNA (Diploid)No nuclear membraneCircular DNA (Haploid) Cytop
4、lasmic structures Mito, Golgi, ERRespiration+Via mitochondria-Via cytoplasmic membraneEukaryote vs. ProkaryoteBacterial Ultra-structureGram-positive vs. Gram-negative bacteria1. Gram-positive vs Gram-negative bacteria: - Similar Internal structures - Different External structures. 2. The cytoplasm o
5、f the bacteria contains - DNA chromosome, mRNA, ribosomes, proteins, and metabolites. 3. The bacterial chromosome - A single copy (haploid) and double-stranded circle in a discrete area known as the nucleoid. - No histonesCytoplasmic Structures-I4. Plasmids (質體) : - Smaller, circular, extrachromosom
6、al DNAs - Most commonly found in gram-negative bacteria - Not essential for cellular survival - Provide a selective advantage: many confer resistance to one or moreantibiotics. Cytoplasmic Structures-II1. The cytoplasmic membrane - A “lipid bilayer structure” similar to that of the eukaryotic membra
7、nes - Contains no steroids (e.g., cholesterol); mycoplasmas are the exception. 2. Involves in electron transport and energy production, which are normally achieved in mitochondria in eukaryotes. Cytoplasmic Membrane-I3. Contains transport proteins = exchange metabolites ion pumps = a membrane potent
8、ial4. Mesosome - A coiled cytoplasmic membrane - Acts as an anchor to bind and pull apart daughter chromosomes during cell division.Cytoplasmic Membrane-IIBacterial Cytoplasmic MembraneATP production machinery1. The structure components and functions of the cell wall distinguish gram-positive from g
9、ram- negative bacteria. (A). Gram positive bacteria:(1) Peptidoglycan (murein, mucopeptide)(2) Teichoic acid（胞壁酸) they are composed of protein subunits (pilin).2. Fimbriae can be morphologically distinguished from flagella because they are smaller in diameter (3 to 8 nm versus 15 to 20 nm) and usual
10、ly are not coiled in structure.3. They may be as long as 15 to 20 m, or many times the length of the cell. 4. Fimbriae promote adherence to other bacteria or to the host (alternative names are adhesins, lectins凝集 素, evasins逃避素, and aggressins攻擊素).Fimbriae (pili): Latin for “fringe”5. As an adherence
11、 factor (adhesin黏附素), flmbriae are an important virulence factor for E. coli colonization and infection of the urinary tract, for Neisseria gonorrhoeae and other bacteria. 6. The tips of the fimbriae may contain proteins (lectins) that bind to specific sugars (e.g., mannose).7. F pili (sex pili) pro
12、mote the transfer of large segments of bacterial chromosomes between bacteria. These pili are encoded by plasmid (F).Fimbriae (pili): Latin for “fringe”1. Some gram-positive bacteria, but never gram-negative such as : Bacillus (b) the bare minimum concentrations of essential proteins and ribosomes;
13、(c) High concentration of Ca2+ chelate of DPA (Ca-DPA, dipicolinic acid)(砒啶甲酸) . = DPA appears to be important in spore core dehydration and concomitant spore heat resistance.6. The structure of the spore protects the genomic DNA from desiccation, intense heat, radiation, and attack by most enzymes
14、and chemical agents.Spores (芽胞)-II7. Depletion of specific nutrients (e.g., alanine) from the growth medium triggers a cascade of genetic events (comparable to differentiation) leading to the production of spore.8. Spore mRNA are transcribed and other mRNA are turned off. Dipicolinic acid(DPA) is pr
15、oduced.9. Spore structure: Core: one copy of DNA and cytoplasmic contentsInner membrane and Spore wall Cortex: peptidoglycan layer Coat: Keratine-like protein which protect the spore. Exosporium:外胞壁Spores (芽胞)-IIISpore structure: Core: one copy of DNA cytoplasmic contents Inner membrane Spore wallCo
16、rtex: peptidoglycan layerCoat: Keratine-like protein which protect the spore.Exosporium:外胞壁Thank You & The End 10. Germination: The germination of spores into the vegetative is stimulated by disruption of the outer coat by stress, pH, heat, or another stressor and requires water and a triggering nutrient (e.g., alanine). 11. The process takes about 90 minutes. 12. Once the germination process has begun, the spore will take up water, swell, shed its coats (脫除外套) , and produ
