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micrometer
=0.000001m (10neg6 m) the prefis micro indicates that the unit following it should be divided by 1million.
nonometer
=0.00000001m (10neg9m)
Light microscopy
refers to the use of any kind of microscope that uses visible light to observe specimens
Compound light microscope
has a series of lenses and uses visible light as its source of illumination.
illuminator
the light source
condenser
which has lenses that direct the light rays through the specimen
objective lenses
the leses closest to the specimen
ocular lens
eyepiece
total magnification
calculates by multiplying the objective lens magnification (power) by the ocular lens magnification (power)
Resolution
(also called resolving power) is the ability of the lenses to distinguish fine detail and structure.
Refractive index
a measure of the light-bending ability of a medium. we change the refractive index of specimens by staining them.
Immersion Oil
Used only with the 100X objecive, The immersion oil has the sam refractive index as glass, so the oil becomes part ofthe optics of the glass of the microscope. inless immersion oil is used, light rays are refacted as they enter te air from the slide, and the objective lens would have to be increased in diameter to capture most of them. If oil is not used the image becomes fuzzy
Brightfield illumination
focusing the light, the condenser produces a brighfield illumination.
Darkfield mocroscope
used for examining live micoorganisms that either are invisible in the ordinary light microscope, cannot be stained by standard methods, or are so distorted by staining that thier characteristics then cannot be identified. A drkffield microscope uses a darkfield condenser that contains an opaque disc. There is no direct backround light, the specimen appears light against a black backround-the dark field.
Antibodies
natural defense molecules that are produced by humans and many animals in reaction to a fforeign substance, or antigen.
electron microscope
in electron microsocopy, a beam of electrons is used instead of light. The better rresolution of electron microscopes is due to the shorter wavelengths of electrons.
Transmission electron microscope (TEM)
is a finely focused beam of electrons from an electron gun passes through a specially prepared, ultrathin section of the specimen.
Scanning electron microscope
overcomes the problem of sectioning associated with a transmission electron microscope. A scanning electron microscope provides striking 3-D views of specimens.
Staining
coloring the microorganisms with a dye that emphasizes certainn structures.
fixed
(atached) to the microscope slide. Fixing simultaneously kills the microorganisms and fixes or sticks them to the slide.
smear
when a specimen is to be fixed, a thin film of material containing the mircoorganisms is spread over the surface of the slide. This film, called a smear, is allowed to air dry
Chromophore
Stains are salts composed of a positive and negative ion, one of which is colored and is known as the chromophore.
Basic dyes/Acidic dyes
basic dyes: positive ion Acidic dyes: in the negative ion **Bacteria are slightly negatively charged at pH7.
Basic Dyes
include crystal violet, methylene blue, malachite green, and safranin, are more commonly used than acidic dyes.
Negative staining
Preparing colorless bacteria agins a colored background is called negative staining.
Simple stain
an aqueous or alcohol solution of a single basic dye.
Mordant
a chemical is added to the solution to intensify the stain. One function of a mordant is to increase the affinity of a stain for a biological specimen; another is to coat a stucture (such as a flagellum) to make it thicker and easier to see after it is stained with a dye. Simple stains: methylene blue, carbolfuchsin, crystal violet, and safranin
Differential stains
react differently with different kinds of bacteria and thus can be used to distinguish among them. **the diffeential stains most frequently used for bacteria are the Gram stain and the acid-fast stain.
Gram stain
one of the most useful staining procedures beccause it classifies bacteria into two large groups: Gram-positive and Gram-negative.
Primary Stain
a heat fixed smear is covered with a basic purple dye, usually crystal violet, it imparts its color to all cells
decoloriaing agent
an alcool=acetone solution, which removes the purple from the cells fo som species but not from others.
Gram Positive
Bacteria that rretain color after the alcohol has attempted to decolorize them are classiffied as gram-positive
Gram Negative
Bacteria that lsoe the dark violet or purple color after decolorization are classified as gram-neegative.
Counterstains
Safranin is applied because it turns the gram-negative bacteria pink. Stains such as safranin that have a contrasting color to the promary stain are called counterstains. **Because gram-positive bacteria retain the original purple stain, they are not affected by the counterstain.
Acid-Fast Stain
One that differentiates bacteria into distinctive groups is the acid fast stain, it binds strongly only to baccteria that have a waxy material in thier cell walls. Microbiologists use this stain to identify all bavteria in the genus Mycobacterium.
Special Stains
are used to color and isolate specific parts of microorganisms, such as endospores and flagella, and to reveal the presence of capsules.
Capsule
A gelationous covering, that covers many microorganisms.
Virulence
the degree to which a pathogen can cause disease.
Endospore
a special resistant, dormant structure formed within a cell that protects a bacterium from adverse environmental conditions. Endospors cannot be stained by gram staining because the dyes do not penetrate the wall of the endospore. Endospore stain is done on a hot plate because the heat helps the stain penetrate the endospore wall.
Flagella
Structures of locomotion too small to be seen with a light microscope without staining.
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