Microbiology Exam 1
Microbiology Exam 1 BSC 302
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This 5 page Study Guide was uploaded by Annie Hopkins on Monday February 8, 2016. The Study Guide belongs to BSC 302 at Marshall University taught by Dr. Jennifer Mosher in Summer 2015. Since its upload, it has received 90 views. For similar materials see Principles of Microbiology in Biology at Marshall University.
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Date Created: 02/08/16
Chapter 2 Resolution is the smallest distance by which two objects can be separated and still be distinguished Detection is the ability to determine the presence of an object Magnification means an increase in the apparent size of an image to resolve smaller separations between objects Bacilli = rods Cocci = spheres Spiral forms – Spirilla Absorption means that the photon’s energy is acquired by the absorbing object Reflection means that the wavefront bounces off the surface of an object Refraction is the bending of light as it enters a substance that slows its speed Scattering occurs when the wavefront interacts with an object smaller than the wavelength of light Magnification requires the bending of light rays, as in refraction Parallel rays each bend at an angle such that all of the rays meet at a certain point, called the focal point Magnification without increasing detail is called empty magnification Light rays actually form wave fronts, which undergo interference Bright Field Microscopy- Generates a dark image of an object over a light background Compound microscope is a system of multiple lenses designed to correct or compensate for aberration - Ocular lens - Objective lens - Need to be parfocal Total magnification = magnification of ocular multiplied by that of the objective Wet Mount- a drop of water on a slide with a coverslip Fixation = cells are made to adhere to a slide in a fixed position Staining = cells are given a distinct color Simple stain adds dark color specifically to cells, but not to the external medium or surrounding tissue Differential stain stains one kind of cell but not another Gram-positive bacteria retain the crystal violet stain because of their thicker cell wall Gram-negative bacteria do not Acid-fast stain = carbolfuchsin used to stain Mycobacterium species Spore stain = malachite green used to detect spores of Bacillus and Clostridium Negative stain = colors the background, which makes capsules more visible absorbs light of a specific wavelength (the excitation wavelength), then emits light at a longer wavelength (the emission wavelength) fluorophore is a fluorescent chemical compound Dark-field optics enables microbes to be visualized as halos of bright light against darkness Transmission electron microscopy (TEM)- Electrons pass through the specimen - Reveals internal structures Scanning electron microscopy (SEM)- Electrons scan the specimen surface- Reveals external features in 3D Chapter 3 Cytoplasm = consists of a gel-like network Cell membrane = encloses the cytoplasm Cell wall = covers the cell membrane Nucleoid = non-membrane-bound area of the cytoplasm that contains the chromosome in the form of looped coils Flagellum = external helical filament whose rotary motor propels the cell The structure that defines the existence of a cell is the cell membrane phospholipid consists of glycerol with ester links to two fatty acids and a phosphoryl head group two layers of phospholipids in the bilayer are called leaflets Small uncharged molecules, such as O2 and CO2, easily permeate the membrane by diffusion Water tends to diffuse across the membrane in a process called osmosis Passive transport = molecules move along their concentration gradient Active transport = molecules move against their concentration gradient In eukaryotic membranes, the reinforcing agents are sterols, such as cholesterol In bacteria, the same function is filled by hopanoids, or hopanes Hydrocarbon chains are branched terpenoids sacculus, consists of a single interlinked molecule Most bacterial cell walls are made up of peptidoglycan Gram-positive bacteria (thick cell wall) Gram-negative bacteria (thin cell wall) Capsule (not all species)- Made of polysaccharides S-Layer (not all species)- Made of protein Amino acid cross-links in peptidoglycan Teichoic acids for strength FtsZ = forms a “Z-ring” in spherical cells MreB = forms a coil inside rod-shaped cells CreS “crescentin” = forms a polymer along the inner side of crescent-shaped bacteria Signal recognition particle (SRP) binds to the growing peptide Polymerase with the help of accessory proteins (the replisome) Thylakoids = extensively folded intracellular membranes Carboxysomes = polyhedral bodies packed with the enzyme Rubisco for CO2 fixation Gas vesicles = to increase buoyancy Storage granules - Glycogen, PHB, and PHA, for energy - Sulfur, for oxidation Magnetosomes - Membrane-embedded crystals of magnetite, Fe3O4 - Orient the swimming of magnetotactic bacteria Pili- are straight filaments of pilin protein - Used in attachment Sex pili are used in conjugation Stalks are membrane-embedded extensions of the cytoplasm - Tips secrete adhesion factors called holdfasts Nanotubes are intercellular connections that pass material from one cell to the next Peritrichous cells have flagella randomly distributed around cell Lophotrichous cells have flagella at the end(s) Monotrichous cells have a single flagellum Note: flagella rotate either clockwise (CW) or counterclockwise (CCW) relative to the cell Attractants cause CCW rotation Repellents cause CW rotation Chapter 4 Essential nutrients are those that must be supplied from the environment Macronutrients - Major elements in cell macromolecules - C, O, H, N, P, S - Ions necessary for protein function - Mg2+, Ca2+, Fe2+, K+ Micronutrients - Trace elements necessary for enzyme function - Co, Cu, Mn, Zn Defined minimal medium contains only the compounds needed for an organism to grow Autotrophs fix CO2 and assemble into organic molecules (mainly sugars) Heterotrophs use preformed organic molecules Phototrophs obtain energy from chemical reactions triggered by light Chemotrophs obtain energy from oxidationreduction reactions Lithotrophs use inorganic molecules as a source of electrons Organotrophs use organic molecules Nitrogen fixers possess nitrogenase, which converts N2 to ammonium ions (NH4 + ) Nitrifiers oxidize ammonia to nitrate (NO3 – ) Denitrifiers convert nitrate to N2 Protist algae, such as single-celled Euglena, are mixotrophic Coupled transport systems are those in which energy released by moving a driving ion down its gradient is used to move a solute up its gradient Symport the two molecules travel in the same direction Antiport the actively transported molecule moves in the direction opposite to the driving ion The largest family of energy-driven transport systems is the ATP-binding cassette superfamily, or ABC transporters Uptake ABC transporters are critical for transporting nutrients Efflux ABC transporters are generally used as multidrug efflux pumps Siderophores are specialized molecules secreted to bind ferric ion (Fe3+) and transport it into the cell Group translocation is a process that uses energy to chemically alter the substrate during its transport Dilution streaking - Dragging a loop across the surface of an agar plate Spread plate - Tenfold serial dilution is performed on a liquid culture - A small amount of each dilution is then plated Complex media are nutrient rich but poorly defined Synthetic media are precisely defined Enriched media are complex media to which specific components are added Selective media favor the growth of one organism over another Differential media exploit differences between two species that grow equally well Streak plate - Dragging a loop across the surface of an agar plate Spread plate - Tenfold serial dilutions are performed on a liquid culture - A small amount of each dilution is then plated Viable cells can be counted via the pour plate method Microorganisms can be counted indirectly via biochemical assays of cell mass, protein content, or metabolic rate. - Also by measuring optical density Binary fission, where one parent cell splits into two equal daughter cells Growth rate, or rate of increase in cell numbers or biomass, is proportional to the population size at a given time Generation time is the time it takes for a population to double simplest way to model the effects of a changing environment is to culture bacteria in a batch culture continuous culture, all cells in a population achieve a steady state chemostat ensures logarithmic growth by constantly adding and removing equal amounts of culture media surface-attached communities called biofilms
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