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Lab midterm
Pg 1-9
22
Microbiology
Undergraduate 2
02/23/2011

Additional Microbiology Flashcards

 


 

Cards

Term
What are the important parts of a microscope?
Definition
  1. Framework: arm
  2. Stage: holds slide and moves it around stage
  3. Lens system

-Oculars: eyepiece lenses

-Objectives: lenses attached to rotable nosepiece (4x,10x,45x,100x-oil immertion lens-)

-Condenser: directs light towards objective lens

-Iris Diaphragm

Term
What can be possibly done to improve resolution (resolving power)?
Definition

d, which is the smallest distance between two objects which can be seen as separate, can be decreased by lowering λ(wavelength of light) or increasing the NA(numerical aperture)

 

d=λ/2NA

Term
What is the formula to determine the total magnification of an object in a compound microscope?
Definition

Mag(total)= Mag(objective) * Mag(ocular)

 

-Objective: nosepiece lens (4x,10x,45x,100x)

-Ocular: eyepiece lens (usually 10x)

Term
What are the 3 principle forms of microorganisms revealed by a light microscope?
Definition
  1. Cocci: more or less spherical organisms
  2. Bacilli: Cylindrical organisms
  3. Helicoidal: Spiral shaped
Term
What are the different patterns in which cocci may appear when incompletely separated?
Definition
  • Diplococci(pairs): divide in one plane
  • Steptococci(chains): divide in one plane
  • Tetracocci(tetrads): divide in two planes
  • Staphylococci(clusters): divide in three planes irregularly
  • Sarcinae(cuboidal packets): divide in three planes regularly
Term

What are the different cylindrical shapes in which Bacilli can appear?

 

Definition
  • Coccobacillus: very short, spherical, slightly longer in one direction than other.
  • Fusiform Bacilli: tapered at the ends, 'football' shaped
  • Filamentous Bacillary: forms grow in long threds
Term
What are dyes?
Definition
Organic compounds containing a chromophore with affinity for cellular material.
Term
What are the different types of dyes?
Definition
  • Cationic: basic dyes, + charged chromophore

Methylene Blue, Crystal Violet

  • Anionic:acidic dyes,- charged chromophore

Acid fuschin, Congo Red, Nigrosin

  • Fat soluble:no charge

Sudan Black Stain granules of Poly0B-OH-Butyric acid

  • Insoluble Dyes:water insoluble

India Ink

Term
What are the types of staining procedure?
Definition
  1. Negative Staining
  2. Simple Staining
  3. Differential Staining
  4. Structural Staining
Term
Explain the negative stain procedure
Definition
  • Stains background, not the cell in brightfield microscopy
  • Uses 2 dyes:
  • Nigrosin-black anionic charged dye, repelled by the - charged surface of bacterial cell
  • India Ink-(colloidal suspension of carbon particels) doesn't penetrate cell surface

 

Term
Explain the simple stain procedure
Definition
  • One dye used to stain all cells the same color. Can be used to tell morphology and size. Cationic (+) dyes are attracted by ionic forces to the - charged surface of bacterial cell.
  • Common dyes are methylene blue and crystal violet.
Term

Explain differential stain procedure

 

Definition
  • Causes cells to stain differently based on properties of the cell
  • Two examples are:
  • Gram Stain
  • Acid Fast Stain
Term
Explain Gram stain procedure.
Definition
  • Causes the cell to stain differently based on characteristics of their cell wall.
  • Gram+ microorg. have a higher peptidoglycan and lower lipid content than Gram-.
  • Cells are stained with crystal violet, then fixed with iodine forming a crystal violet-iodine complex within the cell. Ethanol is then added as a decolorizer.(Gram- cells are easily decolorized because the ethanol dissolves the high lipid cell wall allowing the crystal violet-iodine complex to readily exit the cell. Gram+ cells resist decolorization due to the difference in cell wall consistency retaining the crystal violet-iodine complex). The Gram- cells are then counterstained with saffranin.

 

Term

Explain Acid Fast Stain

 

Definition
  • Acid fast microorganisms have a high wax content in their walls, which requires the use of steam to allow dye to penetrate the cell.
  • Cells are steamed in the presence of carbol fuschin and decolorized with acid alcohol.
  • Cells which are "acid fast" will not decoloried and remain red, while non acid fast organisms will readily lose their stain and become colorless.
  • These cells are then counterstained with Methylene blue.
Term
What are the two genera of Acid fast organisms?
Definition
  • Mycobacterium: Do not gram stain well if mature because of high wax content within walls (if youn appear as gram + tapered rods that sometimes fragment)
  • Two important species: Tuberculosis and leprae
  • Nocardia
Term
Explain structural staining
Definition
  • Spore staining: To stain spores, the cells must be steamed to allow for the dye (malachite green)to enter the spores.Once the spores are stained, all other microorganisms can be easily decolorized with water. The other microorganisms and vegetative cells are then counterstained with Safranin.
  • Endospores: green center with a pink sporangium
  • Free spores:small green oval bodies
Term
What are the 3 genera of spore forming organisms?
Definition
  1. Bacillus: areobic, gram+ rod
  2. Clostridium: anaerobic, gram+ rod
  3. Sporsacinae: cocci

-Anaerobic green: endospore/free spores clostridium

-Aerobic green: endospore/free spores of bacillus

-Anaerobic pink:vegetative/sporangia of clostridium

-Aerobic Pink:vegetative/sporangia of bacillus

 

Term
What are the five methods of tube media transfer?
Definition
  1. Pour: 15-20 ml of liquid agar used to pour into plate
  2. Broth: 5-7 ml of liquid media
  3. Deep: 5-7 ml of media which has solidified in an upright position
  4. Slant: 5-7ml of media which has solidified at an angled position
  5. Fermentation broth: broth with Durham Tube added
Term
What is natural media?
Definition
media composed of complex raw materials whose actual chemical composition is unknown (nutrient agar)
Term
What is synthetic media?
Definition
Media whose exact chemical composition is known and in many instances is design for isolation,selection or differentiation of specific types of microorganisms.
Term
What are the 2 types of synthetic media?
Definition
  1. Selective media: a media which favors the growth of one type of microorganisms over another. Accomplished by either inhibiting unwanted microorganisms or enriching
  2. Differential media: a media which differentiates or distinguishes between different types of microorganisms based on differences in appearance of growth or color changes.
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