Microbiology Chapter 3

Front 1

Acid fast positive, such as tuberculosis, is colored

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red

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non acid fast is colored

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blue

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total magnification =

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objective lens x ocular lens

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resolution

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the ability of the lenses to distinguish between two points

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shorter wavelengths of light provide

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greater resolution

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refractive index

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a measure of the light-bending ability of a medium

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immersion oil is used to...

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keep light from bending

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brightfield illumination

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light reflected off the specimen does not enter the objective lens

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darkfield illumination

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light reflected off the specimen enters the objective lens

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phase-contrast microscopy

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accentuates diffraction o the light that passes through a specimen, good for viewing internal structures of unstained specimens

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differential interference contrast microscopy

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accentuates diffraction of the light that passes through a specimen, uses two beams of light

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flourescence microscopy

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uses UV light, fluorescent substances absorb UV light and emit visible light; cell may be stained with fluorescent dyes, useful to specifically id pathogens in specimens

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fluorochromes

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fluorescent dyes

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confocal microscopy

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can create a 3D image
cells tained with flurochrome dyes, the short wavelength (blue) light is used to excite the dyes, and the light illuminates each plane in a specimen to produce a 3D image up to 100 um deep

Front 15

two-photon microscopy

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used to study cells attached to a surface; cells are stained with fluorochrome dyes; thwo photons of long-wavelength (red) light are used to excite the dyes;

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scanning acoustic microscopy

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used to study cells attached to a surface (such as a catheter tip); measures sound waves that are reflected back from an object

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electron microscopy

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uses electrons instead of light;
the shorter wavelength of electrons gives greater resolution

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transmission electron microscopy (TEM)

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uses ultrathin section of specimen;
light passes through specimen, through an electromagnetic lens, to a screen or film;
specimens may be stained with heavy metal salts

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scanning electron microscopy (SEM)

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produces 3D images;
an electron gun produces a beam of electrons that scans the surface of a whole specimen;
secondary electrons emitted from the specimen produce the image

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scanning tunneling microscopy (STM)

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uses a metal probe to scan a specimen

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scanned-probe microscopy aka atomic force microscopy (AFM)

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uses a metal-and diamond probe inserted into the specimen to new 3D images

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staining

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coloring the microbe with a dye that emphasizes certain structures

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smear

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a thin film of a solution of microbes on a slide

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purpose of fixing a smear

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to attach the microbes to the slide and kill the microbes

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in a basic dye, the chromophore is a

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cation

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in an acidic dye, the chromophore is a

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anion

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negative staining

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staining the background instead of the cell

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simple stain

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use of a single basic dye

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mordant

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may be used to hold the stain or coat the specimen to enlarge it

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differential stains

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are used to distinguish between bacteria;
include the gram stain and acid-fast stains

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gram positive bacteria tend to be killed by

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penicillin and detergents

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gram negative bacteria are more or less resistent to antibiotics

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more resistant

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why is gram negative more resistant to antibiotics?

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the cell wall has more lipids and is more water insoluble

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what is the #1 nosocomial infection

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E. coli

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gram stain primary stain

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crystal violent

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gram stain mordant

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iodine

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gram stain decolorizing agent

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alcohol-acetone

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gram stain counterstain

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safranin

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color of gram positive cells after safranin

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purple

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color of gram negative cells after safranin

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red

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myco-

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fungal

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what is different about an acid-fast cell

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the stained waxy cell wall is not decolorized bhy acid-alcohol

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what are two acid-fast cells

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Mycobacterium (TB)
Nocardia
leprasy

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acid-fast stain primary stain

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carbolfuchsin

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acid-fast stain decolorizing agent

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3% acid 97% alcohol

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acid-fast stain counterstain

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methylene blue

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color of acid-fast cell after methylene blue

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red

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color of non-acid-fast cell after methylene blue

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blue

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capsule staining

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negative stain and cells also stained; capsule appears as white halo around cell

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endospore stain primary stain

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malachite green, usually with heat

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endospore stain decolorizing agent

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water

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endospore stain counterstain

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safranin

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flagella staining uses

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mordant on flagella;
carbolfuchsin simple stain

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a micrometer is equal to

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10-6 m or .000001 m

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a nanometer is equal to

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10-9 m

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first simple microscope

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by van Leeuwenhoek, single lens, 300x

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most ocular lens magnify by

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10x

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quorum sensing

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the ability of bacteria to communicate and coordinate behavior. bacteria that use quorum sensing produce and secrete a signaling chemical called an inducer

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example of a gram positive bacteria

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Staphylococcus epidermis
Bacillus subtilis

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example of a gram negative bactera

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E. coli