PORTAGE MICROBIOLOGY EXAM 3
A negative stain is only mildly invasive and may not kill the microorganism; as such, a negative stain is
contraindicated for ___________________. - -Pathogenic samples
-Acid-fast staining procedure uses the red dye ______________, initially staining all cells red - -
carbolfuchsin
-As light passes through a microscope, what is the last piece that light passes before reaching your eyes?
- -the ocular lens, or eyepiece, directly into your eye.
-before the light reaches the sample, it first passes through a ________________ converging the light
beams into a focused area on the sample - -condenser
-Contrast - -the difference in light absorbance between two objects.
-Giemsa stain - -combined with Wright's stain, the resulting combinatorial stain can be applied to blood
smears to determine the presence (or absence) of pathogenic bacteria—human (blood) cells appear
purple and bacterial cells appear as pink
-Gram negative bacteria - -Bacteria that have a thin peptidoglycan cell wall covered by an outer plasma
membrane. They stain very lightly (pink) in Gram stain. Gram-negative bacteria are typically more
resistant to antibiotics than Gram-positive bacteria. Outer membrane is composed of LPS
-Gram staining is based on what basic principle? - -Gram staining, developed by Hans Christian Gram in
1884, began with the basic observation that different types of bacteria react differently to various dyes.
Some bacteria readily take up a specific dye while others do not.
-How is the total magnification of an object calculated? - -Total magnification is calculated by multiplying
the power of the objective and the power of the eyepiece.
-If you wish to increase the amount of light going into a microscope, what part would you adjust? - -The
iris diaphragm
-In acid-fast staining, following the decolorization wash step, only cells with a thick ____________
protective membrane remain red - -lipid-based
-micrometer - -one millionth of a meter, 10^ -6
-most common method to fix a sample - -heat fixation
-nanometer - -one billionth of a meter, 10^-9
-Negative charge - -applying nigrosin (or India ink) to a sample, its _________________ is repelled by the
negatively charged membrane resulting in a sharp contrast between the unstained specimen and the
now dark background.
A negative stain is only mildly invasive and may not kill the microorganism; as such, a negative stain is
contraindicated for ___________________. - -Pathogenic samples
-Acid-fast staining procedure uses the red dye ______________, initially staining all cells red - -
carbolfuchsin
-As light passes through a microscope, what is the last piece that light passes before reaching your eyes?
- -the ocular lens, or eyepiece, directly into your eye.
-before the light reaches the sample, it first passes through a ________________ converging the light
beams into a focused area on the sample - -condenser
-Contrast - -the difference in light absorbance between two objects.
-Giemsa stain - -combined with Wright's stain, the resulting combinatorial stain can be applied to blood
smears to determine the presence (or absence) of pathogenic bacteria—human (blood) cells appear
purple and bacterial cells appear as pink
-Gram negative bacteria - -Bacteria that have a thin peptidoglycan cell wall covered by an outer plasma
membrane. They stain very lightly (pink) in Gram stain. Gram-negative bacteria are typically more
resistant to antibiotics than Gram-positive bacteria. Outer membrane is composed of LPS
-Gram staining is based on what basic principle? - -Gram staining, developed by Hans Christian Gram in
1884, began with the basic observation that different types of bacteria react differently to various dyes.
Some bacteria readily take up a specific dye while others do not.
-How is the total magnification of an object calculated? - -Total magnification is calculated by multiplying
the power of the objective and the power of the eyepiece.
-If you wish to increase the amount of light going into a microscope, what part would you adjust? - -The
iris diaphragm
-In acid-fast staining, following the decolorization wash step, only cells with a thick ____________
protective membrane remain red - -lipid-based
-micrometer - -one millionth of a meter, 10^ -6
-most common method to fix a sample - -heat fixation
-nanometer - -one billionth of a meter, 10^-9
-Negative charge - -applying nigrosin (or India ink) to a sample, its _________________ is repelled by the
negatively charged membrane resulting in a sharp contrast between the unstained specimen and the
now dark background.
