Microbiology Lab Final UTA Exam|183
Questions and Answers
5 Implicit I's of Microbiology - -Inoculation
Incubation
Isolation
Inspection
Identification
- Inoculation - -Put bacteria on/in a medium
- Incubation - -Let it grow at an optimum temperature
- Isolation - -Separate out individual colonies
- Inspection - -Look at characteristics
- Identification - -Identify microbe based on observations
- Form - -Shape of the whole colony; First thing we see when we examine a
bacterium under the microscope
- Margin - -Edge of colony
- Elevation - -Side view
- Morphology - -Form, Margins, Elevation, and Pigment Production
- Friable - -Crusty growth
- Agar Slants - -Used mainly in media cultivation and maintenance of stock
cultures.
-Dry, flat, spreading edge, friable, translucent, mucoid/butyrous, and filiform
growth
- Filiform - -Dense opaque growth with a smooth edge
- Bacteria are Defined by? - -Their cellular structure and small size
- Pellicle - -Bacteria float on top of medium and produce a type of surface
membrane
- Sediment - -Bacteria sink to the bottom
,- Uniform Fine Turbidity (UFT) - -cloudy growth
- Flocculent - -Clumping growth
- Coccus/Cocci - -Spherical shape, greek for berry
Can occur in chains (streptococci), clusters (staphylococcus), or tetrads
(groups of four)
- Bacillus/Bacilli - -Rod shaped, latin for little staff
Rounded, flat tapered ends (fusiform) and can either be motile or non-motile
- Spirillum/Spirilli - -Rigid curved or spiral shaped bacteria, latin for little coil
- Vibrio - -Gently curved rods
- Spriochetes - -Slender, flexible spirals, greek for coil of long hair
- Filamentous Bacteria - -Form long multi-nucleated filamentous hyphae that
may branch to produce mycelium
- Pleomorphic - -Misc. category
-Many bacterium are variable in shape and cannot be characterized by a
single form. Most of these bacteria assume general rod shapes (different
from bacilli) and can assume squares, star shapes, and cocci-bacilli
- Bacterial Smear - -Emulsion of bacteria, spreading bacteria on glass slide
Smear prepared from liquid (broth) or from an agar plate (requires drops of
water). Add DI water when smearing from a plate to the slide but not when
smearing broth!
Should not be too thick or thin
Always vortex liquid media beforehand
- Why do we stain bacteria? - -Bacteria have same refractive index as water.
These allow cells and internal structures to become more visible
- Heat Fixation - --Heat fix slide only after preparing a bacterial smear
-Pass slide through Bunsen burner flame using a microscopic slide holder
- Pros of Heat Fixation - -Kills the bacteria
Fixes bacteria to the slide, ensures against specimen decay over time
Helps with biochemical reactions
, - Cons of Heat Fixation - -Cell distortion, slide damage, dilution issues
- Basic dyes - -Stains bacteria
Bacteria slightly negative at pH=7
- Acidic dyes - -Stains the background
- Simple Stain - -Aqueous or alcohol solution of single basic dye
- Stains - -Solvent and colored molecule (chromogen + chromophore makes
it up)
- Chromogen - -Positively charged (forms bond with (-) charged bacterial
cell)
- Chromophore - -Part of chromogen that gives stain its color
- Common Basic Stains - -Methlyene blue, Crystal Violet, Safranin (these are
cationic, stain acidic structures)
- Basic Stains - -Apply to heat fixed specimens
- Gram Stain - -A differential stain used to detect difference within or
between cells; differentiates G- and G+
Utilizes:
Crystal Violet: primary stain, 1 min
Gram's Iodine: mordant, 1 min
95% Ethanol: decolorizer, quick less than 15 sec
Safranin: counterstain, 1 min
Named after Hans Christian Gram, 1st test performed when identifying
unknown bacteria; variability exists due to bacterial cell wall response to
dyes
- Gram Positive - -Have thicker peptidoglycan
Will retain primary stain of crystal violet (stain purple) because they have
thick PG that traps the dye among its high degree of teichoic acid crosslinks
- Gram Negative - -Have thin peptidoglycan and outer membrane LPS and a
higher lipid content that is targeted by the alcohol/acetone decolorizer and
makes the cell's outer layers more porous; they are unable to retain CV
primary stain
Questions and Answers
5 Implicit I's of Microbiology - -Inoculation
Incubation
Isolation
Inspection
Identification
- Inoculation - -Put bacteria on/in a medium
- Incubation - -Let it grow at an optimum temperature
- Isolation - -Separate out individual colonies
- Inspection - -Look at characteristics
- Identification - -Identify microbe based on observations
- Form - -Shape of the whole colony; First thing we see when we examine a
bacterium under the microscope
- Margin - -Edge of colony
- Elevation - -Side view
- Morphology - -Form, Margins, Elevation, and Pigment Production
- Friable - -Crusty growth
- Agar Slants - -Used mainly in media cultivation and maintenance of stock
cultures.
-Dry, flat, spreading edge, friable, translucent, mucoid/butyrous, and filiform
growth
- Filiform - -Dense opaque growth with a smooth edge
- Bacteria are Defined by? - -Their cellular structure and small size
- Pellicle - -Bacteria float on top of medium and produce a type of surface
membrane
- Sediment - -Bacteria sink to the bottom
,- Uniform Fine Turbidity (UFT) - -cloudy growth
- Flocculent - -Clumping growth
- Coccus/Cocci - -Spherical shape, greek for berry
Can occur in chains (streptococci), clusters (staphylococcus), or tetrads
(groups of four)
- Bacillus/Bacilli - -Rod shaped, latin for little staff
Rounded, flat tapered ends (fusiform) and can either be motile or non-motile
- Spirillum/Spirilli - -Rigid curved or spiral shaped bacteria, latin for little coil
- Vibrio - -Gently curved rods
- Spriochetes - -Slender, flexible spirals, greek for coil of long hair
- Filamentous Bacteria - -Form long multi-nucleated filamentous hyphae that
may branch to produce mycelium
- Pleomorphic - -Misc. category
-Many bacterium are variable in shape and cannot be characterized by a
single form. Most of these bacteria assume general rod shapes (different
from bacilli) and can assume squares, star shapes, and cocci-bacilli
- Bacterial Smear - -Emulsion of bacteria, spreading bacteria on glass slide
Smear prepared from liquid (broth) or from an agar plate (requires drops of
water). Add DI water when smearing from a plate to the slide but not when
smearing broth!
Should not be too thick or thin
Always vortex liquid media beforehand
- Why do we stain bacteria? - -Bacteria have same refractive index as water.
These allow cells and internal structures to become more visible
- Heat Fixation - --Heat fix slide only after preparing a bacterial smear
-Pass slide through Bunsen burner flame using a microscopic slide holder
- Pros of Heat Fixation - -Kills the bacteria
Fixes bacteria to the slide, ensures against specimen decay over time
Helps with biochemical reactions
, - Cons of Heat Fixation - -Cell distortion, slide damage, dilution issues
- Basic dyes - -Stains bacteria
Bacteria slightly negative at pH=7
- Acidic dyes - -Stains the background
- Simple Stain - -Aqueous or alcohol solution of single basic dye
- Stains - -Solvent and colored molecule (chromogen + chromophore makes
it up)
- Chromogen - -Positively charged (forms bond with (-) charged bacterial
cell)
- Chromophore - -Part of chromogen that gives stain its color
- Common Basic Stains - -Methlyene blue, Crystal Violet, Safranin (these are
cationic, stain acidic structures)
- Basic Stains - -Apply to heat fixed specimens
- Gram Stain - -A differential stain used to detect difference within or
between cells; differentiates G- and G+
Utilizes:
Crystal Violet: primary stain, 1 min
Gram's Iodine: mordant, 1 min
95% Ethanol: decolorizer, quick less than 15 sec
Safranin: counterstain, 1 min
Named after Hans Christian Gram, 1st test performed when identifying
unknown bacteria; variability exists due to bacterial cell wall response to
dyes
- Gram Positive - -Have thicker peptidoglycan
Will retain primary stain of crystal violet (stain purple) because they have
thick PG that traps the dye among its high degree of teichoic acid crosslinks
- Gram Negative - -Have thin peptidoglycan and outer membrane LPS and a
higher lipid content that is targeted by the alcohol/acetone decolorizer and
makes the cell's outer layers more porous; they are unable to retain CV
primary stain
