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276 Microbes Midterm Notes_final.docx

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Wilfrid Laurier University

276 Microbes Midterm Notes Unifying theme: Cells (and microbes) can be viewed as: 1. Biochemical catalysts (metabolism and enzymes) -maintaining a thermodynamic energy flow far from equilibrium defines life -metabolism, differentiation, motility, communication 2. Genetic Coding Devices -ability to do this needs to be kept and transferred History of Microbiology Robert Hooke -England (1635-1703) -first microscope (30X) -micrographia (1665) -cell theory Antoni van Leeuwenhoek -Netherlands (1632-1723) -primitive microscope (50-300X) -“animalcules” – bacteria (1676) -father of microbiology Edward Jenner -England (1749-1823) -small pox vaccination -father of immunology Louis Pasteur -France (1822-1895) -sterilization (downfall of spontaneous generation) -aseptic technique (free of contamination) Ignaz Semmelweis -Vienna (1846) -physicians assistant -childbed fever epidemic Martinus Beikerinick -Holland (1851-1931) -enrichment techniques -metabolic diversity Sergei Winogradsky -Russia (1856-1953) -nutrient cycling (nitrogen/sulfur) -chemolithotrophs Robert Koch -Germany (1843-1910) -germ theory- link between microbes and disease Koch’s Postulates: a) suspected pathogen must be present in all cases of disease and absent in all healthy animals b) suspected pathogen must be grown in pure culture c) cells from pure culture of suspected disease must cause disease in healthy animal d) re-isolate pathogen- must be same as original Prokaryotes (Viruses) Prokaryotes (Bacteria/archaea) -different from other microbes -smaller in size -much smaller -no internal membrane bound organelles -unicellular organisms (one cell) -complex cell walls -genetic potential to replicate but need host -typically divide by binary fission -ribosomes are different and chromosome organization Microbial Eukaryotes Fungi- yeasts, molds Protozoa- free-living or parasitic Algae- photosynthetic eukaryotes ** all are unicellular Shape Arrangement of Bacilli Arrangement of Cocci: Arrangement of Spiral Bacteria: Other Arrangements: Visualizing Microbes! (microscopes) 1. Light Microscopy Microbiology Applications: 2. Atomic Force Microscopy 1. agricultural 2. environmental 3. Electron Microscopy 3. industrial 1. Light Microscopy- Brightfield 4. medical -requires good technique (staining) -condenser focuses light (brightfield) -resolution limit 0.2 um (micrometers up to 1500X) Types of Stain: a) simple: single dye/stain b) differential: multiple dyes/stain c) acid fast: waxy cell walls d) negative: used to visualize capsule (halo around cell) e) endospore: differential stain, schaffer-fulton method d) flagellar: requires layers of stain 2. Light Microscopy- Darkfield -illuminated from the side, not the bottom 3. Light Microscopy- Phase-contrast -phase is light altered as it passes through the specimen -region is in-phase/out-of-phase 4. Light Microscopy- Fluorescence -Definition: ability of organisms to absorb a short wave length of light and emit them at longer wavelengths (1) natural fluorescence under UV light (2) artificial fluorescence 5. Light Microscopy- Differential Interference (DIC) - 2 beams of light split by separate prisms (polarized) -shadows give 3D appearance 6. Light Microscopy- Confocal -0.1 um resolution (twice of other light) -lasers excite fluorochrome stained specimen -computer interface produces final image 7. Atomic Force Microscopy (AFM) -tiny stylus detects weak repulsive forces of atoms -stylus scans specimen surface to build image -living specimen 8. Electron Microscopy (EM) -uses much smaller wavelengths of electrons (not light) -electromagnets focus electrons -in a vacuum, therefore, no live specimen -resolution 0.2 nm (2,000,000 X) -cut thin sections of specimen (20-60 nm) -stained with heavy metals -image is shadow of specimen 8.1 Electron Microscopy- Scanning (SEM) -15-100,000 X -dehydrated, fixed, coated with gold -scattered electrons from surface are collected by photomultiplier -color enhances images 8.2 Electron Microscopy- Cryotomography (cyro-TEM) -rapid freezing to preserve native state of structures -images recorded from different directions  makes 3D 9. X-Rays -0.1-100nm resolution -view viruses (Norwalk) -protein subunits (inside virus) -atomic resolution Characteristics of Life 1) Evolution -archaea are more closely related to eukarya Phylogenetic Trees of Life: a) rRNA b) fatty acid methyl esters (FAME) -lipid content of membranes c) DNA-DNA hybridization -base differences between DNA samples d) GC Ratios -identified whole genome DNA content ratios e) DNA profiling -finger printing/bar-coding f) multi-locus sequencing typing (MLST) -multiplc conserved genes g) whole genome analysis 2) Metabolism – Phylogenetic Development a) Chemolithotrophs: -Energy: oxidation of inorganic chemicals -Carbon: no carbon (inorganic) b) Chemoor
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