Microbiology Lab Midterm Dave Bachoon || 100% Verified
Solutions.
What types of microbes dominate thee air of your microbiology lab? correct answers Bacteria,
fungi, and viruses
Why is it important to use aseptic technique when inoculating tubes and media plates? correct
answers to prevent unwanted organisms (contaminants) from getting in or on experimental tubes
or plates.
How does the procedure for using the microscope differ using high dry power as opposed to low
power? correct answers high power is used for smaller objects and uses fine focus lens, low
power is used for larger objects and uses coarse focus lens
How does loss of light affect the resolution of a specimen? correct answers decreases the
resolution or clarity
What is the purpose of using immersion oil? correct answers refraction of light is minimized and
increases the resolution
What two things can be adjusted to control the amount of light passing into a specimen? correct
answers Iris diaphram and light intensity adjuster
Describe how to properly care for a microscope after immersion oil has been used? correct
answers Remove immersion oil by using a drop of isopropanol (70%) on lens paper
Why must we stain bacteria before examining them with a microscope? correct answers Because
most bacteria lack natural pigmentation, cells are hard to visualize with out first applying a stain
What component of a stain gives bacteria their color? correct answers chromophore group
, What advantage does knowing the morphology and arrangement of a culture provide? correct
answers Each bacterium is best treated with a different antibiotic which is based on the
morphology and arrangement
Why must you use water when preparing a smear from a solid culture? correct answers water
helps to spread the culture over the glass and produces an even and more dilute density
What is a differential stain? correct answers The use of two or more dyes that react differently
with different kinds/parts of bacteria.
How can the age of the cell culture affect the results of a gram stain? correct answers Older
cultures begin to loose the ability to retain the primary dye. Aging of the cells tends to make
them become Gram Neg. even though they are not
Which is the most critical step in the gram staining procedure? correct answers Decolorization- If
you decolorize too vigorously all cells will loose the primary stain and will appear Gram Neg.
Can a bacteria cell produce more than one spore? correct answers No, a cell must lyse in order to
produce an endospore
Why is heat required to stain endospores? correct answers heat is required because you have to
penetrate the cell wall
What is the advantage to the bacteria to produce endospores? correct answers They are resistant
to physical agents (freezing temp., heat, and desiccation) and chemical agents
(antibiotics/bacterides)
Can bacteria survive with a capsule? correct answers Yes
What are the advantages of a capsule to bacteria cells? correct answers provides protection and
helps with resistance
Solutions.
What types of microbes dominate thee air of your microbiology lab? correct answers Bacteria,
fungi, and viruses
Why is it important to use aseptic technique when inoculating tubes and media plates? correct
answers to prevent unwanted organisms (contaminants) from getting in or on experimental tubes
or plates.
How does the procedure for using the microscope differ using high dry power as opposed to low
power? correct answers high power is used for smaller objects and uses fine focus lens, low
power is used for larger objects and uses coarse focus lens
How does loss of light affect the resolution of a specimen? correct answers decreases the
resolution or clarity
What is the purpose of using immersion oil? correct answers refraction of light is minimized and
increases the resolution
What two things can be adjusted to control the amount of light passing into a specimen? correct
answers Iris diaphram and light intensity adjuster
Describe how to properly care for a microscope after immersion oil has been used? correct
answers Remove immersion oil by using a drop of isopropanol (70%) on lens paper
Why must we stain bacteria before examining them with a microscope? correct answers Because
most bacteria lack natural pigmentation, cells are hard to visualize with out first applying a stain
What component of a stain gives bacteria their color? correct answers chromophore group
, What advantage does knowing the morphology and arrangement of a culture provide? correct
answers Each bacterium is best treated with a different antibiotic which is based on the
morphology and arrangement
Why must you use water when preparing a smear from a solid culture? correct answers water
helps to spread the culture over the glass and produces an even and more dilute density
What is a differential stain? correct answers The use of two or more dyes that react differently
with different kinds/parts of bacteria.
How can the age of the cell culture affect the results of a gram stain? correct answers Older
cultures begin to loose the ability to retain the primary dye. Aging of the cells tends to make
them become Gram Neg. even though they are not
Which is the most critical step in the gram staining procedure? correct answers Decolorization- If
you decolorize too vigorously all cells will loose the primary stain and will appear Gram Neg.
Can a bacteria cell produce more than one spore? correct answers No, a cell must lyse in order to
produce an endospore
Why is heat required to stain endospores? correct answers heat is required because you have to
penetrate the cell wall
What is the advantage to the bacteria to produce endospores? correct answers They are resistant
to physical agents (freezing temp., heat, and desiccation) and chemical agents
(antibiotics/bacterides)
Can bacteria survive with a capsule? correct answers Yes
What are the advantages of a capsule to bacteria cells? correct answers provides protection and
helps with resistance
