micro lab test 1
Terms
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- how does a negative stain differ from other stains?
- The dye is acidic and has a negative charge
- What is a benefit of using a negative stain?
- You don't have to heat fix (good for fragile organisms/cells). Also, it produces minimal cell shrinkage.
- What is the theory behind using an acidic stain?
- The negative charge repels the stain, so the cell remains uncolored against a colored background.
- What are two common acidic stains
- nigrosin and eosin
- What is an autoclave bag?
- It is used for decontamination. The items from the bag are put into an autoclave to sterilze them at 121 degrees
- needles and glass should be put in
- sharps container
- bright field microscopy is the
- most commonly used
- the best limit of resolution is
- .2 micrometers
- total magnification is
- mag of objective x mag of ocular
- eyeball to base of microscope
- ocular lens, objective lens, specimin, condensor, light
-
Actual limit of resolution
D= -
wavelength /
NA condensor + NA objective - Numeric Aperture is the
- measure of a len's ability to capture light coming from the specimin and use it to make an image
- stage micrometer
-
used to calibrate microscope
(no numbers on it) - ocular micrometer
- is a scale with uniform incrmenets of unknown size. It has to be callibrated with the objective
-
diplo
strepto
tetrad
sarcina
staphylo -
two cocci
chain cocci
four cocci
eight cocci
grape like structure - bacillus
- rod
- coccobacillus
- short rod that could be confused with cocci
- vibrio
- curved rod
- pleomorphic
- grows in a variety of shapes
- basic steps in making a bacterial smear
- drop water, add bacteria w innoc. loop, spread, air dry (flame loop again), pass through flame
- 2 benefits of making bacterial heat fixed smear?
- it makes the bacteria adhere to the slide and it coagulates the protein to make them more visible
- drawbacks to heat fixing a smear?
- it distorts the cells to an extent.
- theory behind basic stain
- basic stains are attracted to the negative charge on the surface of most bacterial cells. Thuis the cell becomes colored
- 3 common basic stains
- methylene blue, safranin, crystal violet
- how is negative stain different from other stains?
- The dye is acidic and has a negative charge
- examples of differential stains?
- gram, acid fast, capsule, spores or flagella
- differential stains are also referred to as
- structural stains
- what is the Ziehl-Neelsen (ZN) method and sequence of steps
-
Acid fast stain.
heat fix emulsion, cover smear w paper towel and carbolfucshin stain, steam for 5 min, remove paper, rinse, decolorize w acid alcohol, rinse w distilled water, counterstian w M. blue 1 min., blot dry - function of the methylene blue in acid fast?
- It stains the acid fast negative cells
- 2 diseases caused by mycobacteria?
- leprosy and tuberculosis
- function of capsule stain
- detects cells capable of producing an extracellular capsule.
- capsule production
- increases virulence in some microbes, making them less vulnerable to phagocytosis
- capsule technique
- stains around cells. The capsule remains unstained and appears as a white halo against a colored background.
- capsules are composed of
- polypeptides which are difficult to stain
- what is an endospore
- a dormant form of bacterium thatb allows it to survive lean environmental conditions
- Endospore stain process
- heat fixed smear, cover w paper. apply malachite green steam 5 minutes, counterstain w safranin 1 min, rinse, blot dry
- endoposre stain chemicals
- malachite green and safranin
- 2 genera of bacteria w endospores
- bacillus and clostridium
- would bacteria be likely pathogenic at 25 degrees?
- Probably not psychrotrophs, usually are not pathogenic
- would bacteria be likely pathogenic at 37 degrees?
- mesophiles,
- free living
- microbe does not reside on plant or animal host and are not pathogenic.
- opportunistic pathogen
- capable to cause disease
- reservoir
- area including sites outside the host where microbe resides and serves as a poential source of infection
- pathogens
- associated w host
- shape
- circular, irregular, punctiform (tiny, pinpoint)
- margin
- entire (smooth, no irregularites), undulate (wavy), lobate (lobed), filamentous, or rhizoid (branched like roots)
- elevations
- flat, raised, convex, pulvinate (very convex), and umbonate (raised in center)
- texture
- mucoid, moist or dry
- pigment description
- color, opaque, translucent, shiny or dull