MICRO LAB FINAL EXAM
List the three bacterial shapes: Bacilli (rod), Cocci (spherical), and Spirilla (cork-screw)
What is the total magnification when you observe a bacteria with the "oil immersion" objective of your
microscope? 1000x
What does "parfocal" mean? when one lens is in focus, all the other lenses will be in focus with only
minor adjustments of the fine focus
Coarse adjustment vs. Fine adjustment course adjustment: can only use it with the 4x objective lens,
use to raise and lower the stage and bring the specimen into near focus
fine adjustment: focusing under the highest magnification, sharpens the focus quality of the image
present after it is brought into good focus by the coarse adjustment
Iris diaphragm regulates the amount of light passing through the condenser/present on the specimen
being viewed
Condenser (part of microscope) uses its many lenses to concentrate the light from the light source on to
the specimen
True motility purposeful and directional swimming movement
Brownian motility vibration of a particle caused by the unequal collision of water molecules
against it
Streaming motility all objects flow with the movement of the water
What is the purpose of heat-fixing a slide before staining? to make sure all the cells are "fixed" to
the slide to keep them from being washed away
How do Gram positive bacterium appear under the microscope immediately following the ethanol
decolorization step? purple
How do Gram negative bacterium appear under the microscope immediately following the ethanol
decolorization step? clear
Why must the loop be flamed and cooled before use, AND flamed immediately after use? -to
sterilize it so it doesn't contaminate the bacteria
-flamed after to kill the leftover bacteria still on it
-also to protect the microbiologist and the surrounding enviro
, Structural differences between Gram positive and Gram negative bacteria: Gram positive: thick cell
wall with multiple layers of peptidoglycan in their cell wall and NO outer membrane
Gram negative: thin cell wall with one or two layers of peptidoglycan in their cell wall WITH an outer
membrane
5. What is the most important step of a differential stain? Why? Do simple stains have this step? -the
destaining/decolorization step because there is where the bacteria react differently depending on if it is
Gram positive or negative
-simple stains do not have this step
Name the mordant in the Acid fast and Endospore stains heat
Why do endospores require harsh treatment to be stained or killed? they are dense and
impermeable, they are formed in response to harsh conditions
Name a Genus of Bacteria that forms endospores. What color is the endospore and the rest of the
bacteria after an endospore stain? -Bacillus and Clostridium
-after the stain, the endospores are green, and the rest of the bacteria is red
Mycolic acid is found in what Genus of bacteria? How will this bacteria stain in anAcid-Fast stain? Name
a disease caused by Acid Fast bacteria -Mycobacterium and Nocardia
-the acid fast cells will stain red, and non acid fast cells will stain blue
(so the bacterium above will stain red)
-a disease caused by acid-fast bacteria is tuberculosis
Name a reason why capsules are helpful to bacteria. Why are capsule-forming bacteria dangerous to
humans? -capsules can increase a bacterium's ability to cause disease (virulence), survival of
desiccation, and attachment to surfaces
-dangerous to humans tho because once they get in the body there is a high chance of the disease
spreading and since their survival is increased, they also make it harder for humans to kill the bacteria
How can you tell the media is sterile with: Nutrient broth tubes and Nutrient agar plates? Broth
tubes: the liquid will appear clear
Agar plates: clear solid gel with no growth or cloudiness (usually milky white, yellow, greenish, or black)
Streak Plate Method of Isolation -most common and easiest method
-a small droplet of culture or sample is spread across the surface of a medium with an wire loop, this
pattern is used to gradually thin out the sample and separate the cells in order to encourage the growth
of discrete colonies in each quadrant
List the three bacterial shapes: Bacilli (rod), Cocci (spherical), and Spirilla (cork-screw)
What is the total magnification when you observe a bacteria with the "oil immersion" objective of your
microscope? 1000x
What does "parfocal" mean? when one lens is in focus, all the other lenses will be in focus with only
minor adjustments of the fine focus
Coarse adjustment vs. Fine adjustment course adjustment: can only use it with the 4x objective lens,
use to raise and lower the stage and bring the specimen into near focus
fine adjustment: focusing under the highest magnification, sharpens the focus quality of the image
present after it is brought into good focus by the coarse adjustment
Iris diaphragm regulates the amount of light passing through the condenser/present on the specimen
being viewed
Condenser (part of microscope) uses its many lenses to concentrate the light from the light source on to
the specimen
True motility purposeful and directional swimming movement
Brownian motility vibration of a particle caused by the unequal collision of water molecules
against it
Streaming motility all objects flow with the movement of the water
What is the purpose of heat-fixing a slide before staining? to make sure all the cells are "fixed" to
the slide to keep them from being washed away
How do Gram positive bacterium appear under the microscope immediately following the ethanol
decolorization step? purple
How do Gram negative bacterium appear under the microscope immediately following the ethanol
decolorization step? clear
Why must the loop be flamed and cooled before use, AND flamed immediately after use? -to
sterilize it so it doesn't contaminate the bacteria
-flamed after to kill the leftover bacteria still on it
-also to protect the microbiologist and the surrounding enviro
, Structural differences between Gram positive and Gram negative bacteria: Gram positive: thick cell
wall with multiple layers of peptidoglycan in their cell wall and NO outer membrane
Gram negative: thin cell wall with one or two layers of peptidoglycan in their cell wall WITH an outer
membrane
5. What is the most important step of a differential stain? Why? Do simple stains have this step? -the
destaining/decolorization step because there is where the bacteria react differently depending on if it is
Gram positive or negative
-simple stains do not have this step
Name the mordant in the Acid fast and Endospore stains heat
Why do endospores require harsh treatment to be stained or killed? they are dense and
impermeable, they are formed in response to harsh conditions
Name a Genus of Bacteria that forms endospores. What color is the endospore and the rest of the
bacteria after an endospore stain? -Bacillus and Clostridium
-after the stain, the endospores are green, and the rest of the bacteria is red
Mycolic acid is found in what Genus of bacteria? How will this bacteria stain in anAcid-Fast stain? Name
a disease caused by Acid Fast bacteria -Mycobacterium and Nocardia
-the acid fast cells will stain red, and non acid fast cells will stain blue
(so the bacterium above will stain red)
-a disease caused by acid-fast bacteria is tuberculosis
Name a reason why capsules are helpful to bacteria. Why are capsule-forming bacteria dangerous to
humans? -capsules can increase a bacterium's ability to cause disease (virulence), survival of
desiccation, and attachment to surfaces
-dangerous to humans tho because once they get in the body there is a high chance of the disease
spreading and since their survival is increased, they also make it harder for humans to kill the bacteria
How can you tell the media is sterile with: Nutrient broth tubes and Nutrient agar plates? Broth
tubes: the liquid will appear clear
Agar plates: clear solid gel with no growth or cloudiness (usually milky white, yellow, greenish, or black)
Streak Plate Method of Isolation -most common and easiest method
-a small droplet of culture or sample is spread across the surface of a medium with an wire loop, this
pattern is used to gradually thin out the sample and separate the cells in order to encourage the growth
of discrete colonies in each quadrant
