Stokes Microbiology Ch 3
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38 terms
Terms | Definitions |
|---|---|
 micrometer (µm), nanometer (nm) | measurements to measure microorganisms and their structural components: _______ = 0.000001 m = 10⁻⁶ m _______ = 0.000000001 m = 10⁻⁹ m (additionally, picometer = 0.000000000001 m = 10⁻¹² m) |
| simple, compound | ______ microscopes only have one lens (used by van leeuwenhoek, making him the first person to see bacteria); ______ microscopes have multiple lenses |
| light microscopy | the use of any kind of microscope that uses visible light to observe specimens |
| compound light microscope (LM) | an instrument that has a series of lenses and uses visible light as its source of illumination; light goes from the *illuminator* (source) to the *condenser* (directs through specimen) to the *objective lenses* to the *ocular lens* (eye piece) |
| total magnification | ______ = objective lens magnification (power) x ocular lens magnification (usually 10x); |
| resolution (resolving power) | the ability to distinguish fine detail/structure with a magnifying instrument; the ability of the lenses to distinguish two points a specified distance apart (ex/ if 0.4 nm, can distinguish between two points ≥ 0.4 nm); generally, the shorter the wavelength of light used, the greater this is |
| refractive index | a measure of the light-bending ability of a medium; the relative velocity with which light passes through a substance; changed by staining so that specimens are contrasted sharply with their medium under a compound LM |
| immersion oil | oil that is placed between the glass slide and the certain objective lens, so that light rays do not get lost after it passes through the specimen; high magnification with good resolution is achieved |
| brightfield illumination | when dark objects are visible against a bright background; most commonly used in laboratories; can be used with live, unstained, preserved, stain specimens; inexpensive, easy; can see internal structures |
| darkfield microscope | a microscope that has a device to scatter light from the illuminator so that the specimen appears white against a black background; does not distort living cells; shows outline, not internal details |
| phase-contrast microscope | a compound light microscope that allows [more precise] examination of structures inside [living] cells through the use of a special condenser; not necessary to fix/stain (which distorts/kills);two lights: from source and what's reflected/diffracted from a particular structure |
| DIC (Differential interference contrast) microscope | an instrument that provides a three-dimensional, magnified image; similar to phase-contrast (refractive indexes) but uses two beams split by prisms so has higher resolution; shows bright colors and is 3-D |
| fluorescence microscope | a microscope that uses an ultraviolet light source to illuminate specimens that will *fluoresce* (absorb short wavelengths of light [UV] and give off light at a longer wavelength [visible]); cells may be stained with fluorochromes (dyes); used in diagnosing infections (ex/ FA technique) |
| fluorescent-antibody (FA) technique (immunofluorescence) | a diagnostic tool using *antibodies* (natural defense molecules that react to foreign substances called *antigens*) labeled with fluorochromes and viewed through a fluorescence microscope |
| confocal microscope | a light microscope that uses fluorescent stains and laser to make two- and three-dimensional images; similar to fluorescence but only illuminates one plane at a time with short-wavelength (blue) light, resulting in improved resolutions; can scan various depths of specimen up to 100 µm deep |
| TPM (two-photon microscope) | ~ a light microscope that uses fluorescent stains and long wavelength (red) light; allows imaging of living cells in tissues up to 1 mm deep (compared to confocal's 100 µm); less damaging than confocal and can track activity in cells in real time |
| SAM (scanning acoustic microscope) | ~ a microscope that uses high-frequency ultrasound waves to penetrate surfaces; interprets the action of a sound wave sent through a specimen (what is reflected back from an interface within the material); resolution about 1 µm; used to study living cells attached to another surface |
| electron microscope | a microscope that uses electrons instead of light to produce an image (shorter wavelengths give greater resolution); uses electromagnetic lens (not glass); examines objects smaller than about 0.2 µm; always black and white but can be colored artificially for details |
| transmission electron microscope (TEM) | electron microscope that provides high magnifications (10,000-100,000x) of thin sections of specimen; final image is a "micrograph"; resolution: 2.5 nm; metals "stain" to absorb more electrons for more contrast; can see internal structures; preparation to prevent electron scattering kills specimen and can distort ("artifacts" may appear) |
| scanning electron microscope (SEM) | an electron microscope that provides 3-D views of the specimen magnified 1000x-10,000x; "micrograph" final image; useful for surface structures; resolution 10 nm; preparation to prevent electron scattering kills specimen and can distort (adds "artifacts") |
| scanned-probe microscopy | ~ microscopic technique used to obtain images of molecular shapes (see their surface), to characterize chemical properties, and to determine temperature variations within a specimen, all without modification or damaging radiation ex/ STM (scanning tunneling microscopy) and AFM (atomic force microscopy) |
| staining | coloring the sample of microbes with a dye to view through a microscope or emphasize certain structures (before so, the microorganisms must be *fixed* [attached], which kills them but distorts only minimally) |
| smear | a thin film of material containing microorganisms, spread over the surface of a slide (then fixed [by passing over a flame facing up, or covered with methyl alcohol for 1 minute] and stained which is washed off) |
| basic dye, acidic dye | ____ ___: salt (chromophore) in which the color is in the positive ion (cation), used for bacterial stains (bacteria surfaces are slightly negative = attract); ____ ___: chromophore in which the color is in the negative ion (anion), used for *negative staining* (colorless bacteria repel, stains background instead) |
| simple stain | an aqueous or alcohol solution of a single basic dye; to highlight the entire microbe so that shapes and basic structures are visible |
| mordant | chemical added to a staining solution to make it stain more intensely/to coat a structure/specimen to enlarge it; forms large crystals with the dye that are too large to escape the cell wall |
| differential stains | a stain that distinguishes objects into distinctive groups on the basis of reactions to the staining procedure; ex/ Gram stain, acid-fast stain |
| *crystal violet* (purple) (+), *safranin* (basic red) (-) | *Gram stain* (differential stain, classifies bacteria into two groups, gram-positive/gram-negative; dvlped by Hans Christian Gram) procedure: 1. *primary stain* to all cells: ____ ____ 2. iodine (mordant) 3. *decolorizing agent* (alcohol) removes color from gram-neg 4. *counterstained* with ____, then blotted |
| positive, negative | in Gram stains, bacteria that retain purple color after being decolorized = gram-_____; bacteria that lose purple color after being decolorized (then get colored red/pink) = gram-_____ |
| negative, positive | gram-______ bacteria: contain a layer of lipopolysaccharide within their cell wall, thin layer of peptidoglycan, more resistant to antibiotics, easier to destroy with alcohol; gram-______ bacteria: have a thicker peptidoglycan cell wall, teichoic and lipoteichoic acids, CV-I complex (purple) not washed out, tend to be killed by penicillin, lysozyme, detergents |
| acid-fast stain | a differential stain used to identify bacteria that are not decolorized by acid-alcohol; only binds to bacteria that have waxy material (lipids) in their cell walls (*Mycobacterium* tuberculosis/leprosy and *Nocardia*) |
| *carbolfuchsin* (red) (acid-fast), *methylene* (blue) (non-acid-fast/negative) | acid-fast staining procedure: 1. ____ to fixed smear, heated, cooled, washed 2. acid-alcohol (decolorizer) removes red stain from bacteria that are not acid-fast; 3. counterstains with ____ non-acid-fast cells (carbolfuchsin is more soluble in the acid-fast cell wall lipids, non-acid-fast lack lipids) |
| acid-fast, non-acid-fast | ______ retain red color because carbolfuchsin is more soluble in their cell wall lipids than in acid-alcohol; ______ lose red color (then colored blue) because their cell walls lack lipid components |
| special stains | stains used to color and isolate/distinguish specific parts of microorganisms, such as endospores and flagella, and to reveal the presence of capules |
| capsule stain | stain that demonstrates presence of a microbe's gelatinous covering, can determine the organism's *virulence* (degree to which a pathogen can cause disease); done by *negative staining*, then staining the bacteria cells; structure does not accept most dyes, so "halos" appear |
| endospore | special resistant, dormant structure within a cell that protects it from adverse environmental conditions; ordinary stains/dyes do not penetrate wall; highly refractive, can be detected under LM unstained, but cannot be differentiated from inclusions of stored material without special stain |
| endospore staining | Schaeffer-Fulton ______ _______ procedure: 1. primary stain: *malachite green*, heated to steaming 2. decolorized with water for 30 seconds, other parts washed colorless 3. counterstained with safranin |
| flagella staining | a tedious and delicate special staining procedure using mordant and the stain carbolfuchsin to build up the diameters of extremely small structures of locomotion so that it can be seen with a LM |
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