Microbiology Lab Exam | Practice Questions & Verified Answers
what are the safety rules in lab tie hair back
closed toed shoes
wear a lab coat or long-sleeved scrub top during lab
eye protection (if needed/wanted)
wear gloves whenever dealing with live organisms, staining, chemicals, and blood
never put anything in your mouth (chewing gum, applying lip products, biting nails or
pencils)
no pippets in the mouth
wash hands with soap before leaving class
wipe down work area before class and when leaving class
do not leave bunsen burners unattended
What conditions, molecules and nutrients do microbes - nutrients
need to grow? - moister
- proper pH
- suitable O2 level (not all bacteria need O2)
- Suitable temperature
- Sterile
Distinguish between trypticase soy agar (TSA), blood agar TSA
and sabourand dextrose agar (SDA). What organisms can growing bacteria (basically all)
grow on them? How are they different? How are they the Blood agar
same? same as TSA, BUT has sheep red blood cell
also for growing bacteria (basically all)
SDA
best for growing yeast/mold (fungi)
different pH (~5.6 according to google)
Define and be able to identify the dependent, independent, independent: things that CHANGE between experimental group
and standardized variables in an experiment. amount of sunlight
dependent: thing that you're going to MEASURE/count/observe
height of plant
standardized variable: all things that will stay the same
amount/frequency of water, soil (amount and nutrients), the same plant, etc (you
should be able to name a variety!)
What is aseptic technique and why do we use it. set of practice for sterilization to prevent contamination
Describe the process of transferring bacteria from one first you should turn on the Bunsen burner and put the inoculating loop through it for
culture to another without contaminating either culture. a few seconds until the area that will be touched by the microbe turns
reddish/orange
next wait for the inoculating loop to cool for a few seconds to prevent killing off the
microbe with the heat of the tool
when the tool is cooled down, remove the cap from the tube where the microbe is,
and put it through the flame 3 quick times to sterilize the tube
carefully take the tube and insert the inoculating loop through the tube, trying not to
touch the sides of the tube, and only tapping the microbe (no visible amount should
be seen on the loop)
once you take out the tool from the loop (without touching the sides of the tube), put
the tube back in the flame for 3 quick times to sterilize it before putting the cap back
on
next, grab the culture that you are going to mix the inoculating loop with, and also
put it through the flame 3 quick times to sterilize it
carefully transfer the bacteria onto the fresh media once done, flame the tube's
opening, close the tube with the cap, and completely sterilize the tool you used in
the Bunsen burner before setting it down
Draw the streak pattern when you are streaking a bacterial you flame the inoculating loop 5ish times
sample to achieve isolation (quadrant streak). At what you only gather bacteria from the original sample once
points during this process should you flame your
inoculating loop? When do you gather bacteria from the
original sample?
Define "colony" as it is used to describe growth on an agar a colony is a cluster of bacteria
plate in the lab. visible mass of microorganisms that originate from a mother cell, growing on a
medium (like an agar plate)
single microbial cell multiplying into a visible cluster, allowing for easy identification
, Microbiology Lab Exam | Practice Questions & Verified Answers
Identify several characteristics of colonies on a streak plate shape/form: circle, irregular
that can be used to differentiate between different bacterial color: creamy, white, yellow, red, purple, etc
species. margin (edge): appearance of colony's outer boundary (smooth, wavy, lobed,
thread-like)
opacity: amount of light passing through colony (opaque, translucent, transparent)
Review the guidelines for the care, use and cleaning of a care:
microscope. Always carry the microscope with two hands (one on the arm, one supporting the
base).
Keep it upright at all times.
Do not touch the lenses with your fingers.
Only use lens paper for cleaning lenses (never paper towels or clothing).
Store it with the lowest objective lens (4x) in place.
Wrap the cord properly and cover the microscope when not in use.
proper use
Start with the scanning objective (4x).
Place the slide on the stage and secure it with stage clips.
Use the coarse focus knob only on low power.
Switch to higher objectives gradually (10x → 40x).
Use fine focus only on high power (40x).
Adjust light/diaphragm for best contrast.
Always center the image before switching to higher magnification.
cleaning microscope:
Clean lenses only with lens paper before and after use.
Remove immersion oil immediately if used (for 100x oil immersion lens):
Use lens paper + appropriate cleaning solution if needed.
Wipe the stage if it gets dirty.
Never use harsh chemicals or spray directly on lenses.
Make sure everything is dry before storing.
Review the names, locations, and functions of the parts of
the microscope.
Follow the path that light travels from the light source to Light Source --> Iris Diaphragm --> Condenser Lens --> Objective Lens --> Body
your eyes when looking at a specimen through a Tube --> Ocular Lens --> Eye
microscope.
How do you calculate total magnification? TM = (eyepiece)(objective)
Differentiate between a simple stain and a negative stain. simple stain: all cells have more negative charges, we can stain by
How are the stains different? How are the staining using positively charged chromogens (colorful molecules)
protocols different? What do bacteria stained with negative uses methylene blue, crystal violet, safranin
stain look like? How about a simple stain? BACTERIA will look COLORED against light; UNCOLORED BACKGROUND
Simple Staining Protocol:
Place a drop of bacterial suspension on a slide and let it air dry.
Heat-fix the slide by passing it briefly through a flame. This kills the bacteria and
glues them to the glass.
Apply the basic stain and let it sit for a designated period of time (e.g., 1 minute).
Rinse gently with water, blot dry, and view under the microscope.
negative stain: negatively charged chromogen are repelled from cell
will COLOR BACKGROUND; CELLS are WHITE or UNSTAINED
Negative Staining Protocol:
Place a single drop of the acidic stain on one end of the slide.
Mix a small amount of bacteria into the drop of stain.
Use the edge of a second slide to spread the mixture into a thin, feathered film
across the glass.
Allow the slide to completely air dry.
Do not heat-fix the slide. You can view it directly under the microscope since the
lack of heat prevents the bacterial cells from shrinking or distorting
what are the safety rules in lab tie hair back
closed toed shoes
wear a lab coat or long-sleeved scrub top during lab
eye protection (if needed/wanted)
wear gloves whenever dealing with live organisms, staining, chemicals, and blood
never put anything in your mouth (chewing gum, applying lip products, biting nails or
pencils)
no pippets in the mouth
wash hands with soap before leaving class
wipe down work area before class and when leaving class
do not leave bunsen burners unattended
What conditions, molecules and nutrients do microbes - nutrients
need to grow? - moister
- proper pH
- suitable O2 level (not all bacteria need O2)
- Suitable temperature
- Sterile
Distinguish between trypticase soy agar (TSA), blood agar TSA
and sabourand dextrose agar (SDA). What organisms can growing bacteria (basically all)
grow on them? How are they different? How are they the Blood agar
same? same as TSA, BUT has sheep red blood cell
also for growing bacteria (basically all)
SDA
best for growing yeast/mold (fungi)
different pH (~5.6 according to google)
Define and be able to identify the dependent, independent, independent: things that CHANGE between experimental group
and standardized variables in an experiment. amount of sunlight
dependent: thing that you're going to MEASURE/count/observe
height of plant
standardized variable: all things that will stay the same
amount/frequency of water, soil (amount and nutrients), the same plant, etc (you
should be able to name a variety!)
What is aseptic technique and why do we use it. set of practice for sterilization to prevent contamination
Describe the process of transferring bacteria from one first you should turn on the Bunsen burner and put the inoculating loop through it for
culture to another without contaminating either culture. a few seconds until the area that will be touched by the microbe turns
reddish/orange
next wait for the inoculating loop to cool for a few seconds to prevent killing off the
microbe with the heat of the tool
when the tool is cooled down, remove the cap from the tube where the microbe is,
and put it through the flame 3 quick times to sterilize the tube
carefully take the tube and insert the inoculating loop through the tube, trying not to
touch the sides of the tube, and only tapping the microbe (no visible amount should
be seen on the loop)
once you take out the tool from the loop (without touching the sides of the tube), put
the tube back in the flame for 3 quick times to sterilize it before putting the cap back
on
next, grab the culture that you are going to mix the inoculating loop with, and also
put it through the flame 3 quick times to sterilize it
carefully transfer the bacteria onto the fresh media once done, flame the tube's
opening, close the tube with the cap, and completely sterilize the tool you used in
the Bunsen burner before setting it down
Draw the streak pattern when you are streaking a bacterial you flame the inoculating loop 5ish times
sample to achieve isolation (quadrant streak). At what you only gather bacteria from the original sample once
points during this process should you flame your
inoculating loop? When do you gather bacteria from the
original sample?
Define "colony" as it is used to describe growth on an agar a colony is a cluster of bacteria
plate in the lab. visible mass of microorganisms that originate from a mother cell, growing on a
medium (like an agar plate)
single microbial cell multiplying into a visible cluster, allowing for easy identification
, Microbiology Lab Exam | Practice Questions & Verified Answers
Identify several characteristics of colonies on a streak plate shape/form: circle, irregular
that can be used to differentiate between different bacterial color: creamy, white, yellow, red, purple, etc
species. margin (edge): appearance of colony's outer boundary (smooth, wavy, lobed,
thread-like)
opacity: amount of light passing through colony (opaque, translucent, transparent)
Review the guidelines for the care, use and cleaning of a care:
microscope. Always carry the microscope with two hands (one on the arm, one supporting the
base).
Keep it upright at all times.
Do not touch the lenses with your fingers.
Only use lens paper for cleaning lenses (never paper towels or clothing).
Store it with the lowest objective lens (4x) in place.
Wrap the cord properly and cover the microscope when not in use.
proper use
Start with the scanning objective (4x).
Place the slide on the stage and secure it with stage clips.
Use the coarse focus knob only on low power.
Switch to higher objectives gradually (10x → 40x).
Use fine focus only on high power (40x).
Adjust light/diaphragm for best contrast.
Always center the image before switching to higher magnification.
cleaning microscope:
Clean lenses only with lens paper before and after use.
Remove immersion oil immediately if used (for 100x oil immersion lens):
Use lens paper + appropriate cleaning solution if needed.
Wipe the stage if it gets dirty.
Never use harsh chemicals or spray directly on lenses.
Make sure everything is dry before storing.
Review the names, locations, and functions of the parts of
the microscope.
Follow the path that light travels from the light source to Light Source --> Iris Diaphragm --> Condenser Lens --> Objective Lens --> Body
your eyes when looking at a specimen through a Tube --> Ocular Lens --> Eye
microscope.
How do you calculate total magnification? TM = (eyepiece)(objective)
Differentiate between a simple stain and a negative stain. simple stain: all cells have more negative charges, we can stain by
How are the stains different? How are the staining using positively charged chromogens (colorful molecules)
protocols different? What do bacteria stained with negative uses methylene blue, crystal violet, safranin
stain look like? How about a simple stain? BACTERIA will look COLORED against light; UNCOLORED BACKGROUND
Simple Staining Protocol:
Place a drop of bacterial suspension on a slide and let it air dry.
Heat-fix the slide by passing it briefly through a flame. This kills the bacteria and
glues them to the glass.
Apply the basic stain and let it sit for a designated period of time (e.g., 1 minute).
Rinse gently with water, blot dry, and view under the microscope.
negative stain: negatively charged chromogen are repelled from cell
will COLOR BACKGROUND; CELLS are WHITE or UNSTAINED
Negative Staining Protocol:
Place a single drop of the acidic stain on one end of the slide.
Mix a small amount of bacteria into the drop of stain.
Use the edge of a second slide to spread the mixture into a thin, feathered film
across the glass.
Allow the slide to completely air dry.
Do not heat-fix the slide. You can view it directly under the microscope since the
lack of heat prevents the bacterial cells from shrinking or distorting
