Chapter 1-5 Microbiology Study Guide
Exam Questions With Solved Solutions.
In what ways are microorganisms important to humans? - Answer The oxygen we breathe is
the result of microbial activities, as well as the water we drink, the health of our animals, etc.
What is a bacterial colony and how is it formed? - Answer A macroscopically visible population
of cells that is formed from a single cell that has divided many times.
How can you get a pure culture of bacteria and why are pure cultures important? - Answer
Pure cultures usually come from mixed cultures and are very important because they can be
used for experiments that probe the fundamental processes of life.
Where do you find microorganisms and do they typically live in a pure culture? - Answer
Microorganisms are found everywhere. Pure cultures are usually set up to perform
experiments.
What cellular structures distinguish prokaryotic and eukaryotic cells? - Answer -Eukaryotic
cells contain organelles, which includes, most prominently, the DNA-containing nucleus and also
mitochondria and chloroplasts.
-Prokaryotic cells have few internal structures, they lack a nucleus, and they typically lack
organelles.
What are some differences between a cell wall and a cell membrane? - Answer Cell walls are
relatively permeable and much stronger than the cell membrane.
In what types of organisms would you expect to find cell walls and or cell membranes? - Answer
Cell walls are typically found in plant cells and most microorganisms but are not found in animal
cells.
Cell membranes can be found in all cells.
How has the Earth changed over its history? How have microorganisms contributed to these
changes? - Answer 80% of life's history was exclusively microbial; Cyanobacteria provided the
greatest changes because they produced oxygen
,Why were cyanobacteria so important in the evolution of life on Earth? - Answer
Cyanobacteria are so important to the evolution of life on earth because they are responsible
for oxygenating the earth.
What is a genus name of a cyanobacterium and what is unique about these organisms? -
Answer
How do microbes contribute to the nutrition of animals such as humans and cows? - Answer
They allow for the digestion of cellulose through fermentation in ruminant animals. Humans
rely on gut microbiomes to break down complex carbohydrates.
Describe several ways in which microorganisms are important in the food and agricultural
industries. - Answer Although some microbes contribute to the spoilage of food and
foodborne diseases, some are important for the preservation, safety, or even development of
certain foods.
What is wastewater treatment and why is it important? - Answer It is the treatment of water
contaminated with human waste by using microbes so it can be safely reused or returned to the
environment. It is essential to sanitization and human health.
What is the difference between magnification and resolution? - Answer Magnification is the
capacity of a microscope to enlarge an image. Resolution is the ability to distinguish two objects
as distinct and separate.
What is the function of staining in light microscopy? - Answer The function of staining is to
either increase the contrast or to determine which type of cell is present (gram negative/ gram
positive).
What color will a gram-negative cell be after Gram staining by the conventional method? Gram
positive? Why? - Answer Gram negative will be pink, while gram positive will be purple. Gram
positive is purple because it has a thicker cell wall and layer of peptidoglycan which will keep
the crystal violet dye.
What are the steps of a gram stain and the function of each reagent? - Answer 1. flood heat-
fixed smear with crystal violet for one minute (all cells purple)
2. Add iodine solution for one minute (all cells purple)
3. Decolorize w/ alcohol for 20 sec. (gram positive cells=purple, gram negative= colorless)
, What major advantage does phase-contrast microscopy have over staining? - Answer Staining
can kill cells or distort their features, so phase-contrast microscopy allows for viewing of live
specimens.
How can cells be made to fluoresce? - Answer They are made to fluoresce by illuminating
them from above with light of a single color, and filters are used so only fluorescent light is seen.
They either naturally fluoresce due to chlorophyll or artificially fluoresce by dyes.
What are the major differences between electron microscopes and light microscopes? - Answer
Electron microscopes have greater resolution because the wavelength of electrons is much
shorter than visual light's wavelength.
What type of microscope would be used to view the three-dimensional features of a cell? Of the
internal parts of a cell? - Answer -3D: Scanning electron microscope
-Internal parts: Transmission electron microscope
Explain how Pasteur disproved spontaneous generation. - Answer Advocates of the theory
declared that "fresh air" was necessary for spontaneous generation. Pasteur made a flask
designed to allow air to reach the solution after being sterilized but prevented particulate
matter and microorganisms from entering, preventing spoilage of the solution.
Explain Koch's postulates. - Answer Koch's postulate is a set of criteria for proving that a given
microorganism causes a given disease.
What advantages do solid media offer for the isolation of microorganisms? - Answer When a
solid surface was incubated in air, masses of microbial cells developed, each having a
characteristic shape and color.
What is an example of a solid bacteriological medium? Liquid growth medium? - Answer
What is a pure culture? - Answer When a bacteria is isolated and grown away from other
microorganisms in laboratory culture.
Describe Griffith's transformation experiment. - Answer When the disease-causing strain (S) in
the experiment was in the presence of the strain that didn't cause disease (R), it transformed
the R strain into an S strain through genetic transfer.
Exam Questions With Solved Solutions.
In what ways are microorganisms important to humans? - Answer The oxygen we breathe is
the result of microbial activities, as well as the water we drink, the health of our animals, etc.
What is a bacterial colony and how is it formed? - Answer A macroscopically visible population
of cells that is formed from a single cell that has divided many times.
How can you get a pure culture of bacteria and why are pure cultures important? - Answer
Pure cultures usually come from mixed cultures and are very important because they can be
used for experiments that probe the fundamental processes of life.
Where do you find microorganisms and do they typically live in a pure culture? - Answer
Microorganisms are found everywhere. Pure cultures are usually set up to perform
experiments.
What cellular structures distinguish prokaryotic and eukaryotic cells? - Answer -Eukaryotic
cells contain organelles, which includes, most prominently, the DNA-containing nucleus and also
mitochondria and chloroplasts.
-Prokaryotic cells have few internal structures, they lack a nucleus, and they typically lack
organelles.
What are some differences between a cell wall and a cell membrane? - Answer Cell walls are
relatively permeable and much stronger than the cell membrane.
In what types of organisms would you expect to find cell walls and or cell membranes? - Answer
Cell walls are typically found in plant cells and most microorganisms but are not found in animal
cells.
Cell membranes can be found in all cells.
How has the Earth changed over its history? How have microorganisms contributed to these
changes? - Answer 80% of life's history was exclusively microbial; Cyanobacteria provided the
greatest changes because they produced oxygen
,Why were cyanobacteria so important in the evolution of life on Earth? - Answer
Cyanobacteria are so important to the evolution of life on earth because they are responsible
for oxygenating the earth.
What is a genus name of a cyanobacterium and what is unique about these organisms? -
Answer
How do microbes contribute to the nutrition of animals such as humans and cows? - Answer
They allow for the digestion of cellulose through fermentation in ruminant animals. Humans
rely on gut microbiomes to break down complex carbohydrates.
Describe several ways in which microorganisms are important in the food and agricultural
industries. - Answer Although some microbes contribute to the spoilage of food and
foodborne diseases, some are important for the preservation, safety, or even development of
certain foods.
What is wastewater treatment and why is it important? - Answer It is the treatment of water
contaminated with human waste by using microbes so it can be safely reused or returned to the
environment. It is essential to sanitization and human health.
What is the difference between magnification and resolution? - Answer Magnification is the
capacity of a microscope to enlarge an image. Resolution is the ability to distinguish two objects
as distinct and separate.
What is the function of staining in light microscopy? - Answer The function of staining is to
either increase the contrast or to determine which type of cell is present (gram negative/ gram
positive).
What color will a gram-negative cell be after Gram staining by the conventional method? Gram
positive? Why? - Answer Gram negative will be pink, while gram positive will be purple. Gram
positive is purple because it has a thicker cell wall and layer of peptidoglycan which will keep
the crystal violet dye.
What are the steps of a gram stain and the function of each reagent? - Answer 1. flood heat-
fixed smear with crystal violet for one minute (all cells purple)
2. Add iodine solution for one minute (all cells purple)
3. Decolorize w/ alcohol for 20 sec. (gram positive cells=purple, gram negative= colorless)
, What major advantage does phase-contrast microscopy have over staining? - Answer Staining
can kill cells or distort their features, so phase-contrast microscopy allows for viewing of live
specimens.
How can cells be made to fluoresce? - Answer They are made to fluoresce by illuminating
them from above with light of a single color, and filters are used so only fluorescent light is seen.
They either naturally fluoresce due to chlorophyll or artificially fluoresce by dyes.
What are the major differences between electron microscopes and light microscopes? - Answer
Electron microscopes have greater resolution because the wavelength of electrons is much
shorter than visual light's wavelength.
What type of microscope would be used to view the three-dimensional features of a cell? Of the
internal parts of a cell? - Answer -3D: Scanning electron microscope
-Internal parts: Transmission electron microscope
Explain how Pasteur disproved spontaneous generation. - Answer Advocates of the theory
declared that "fresh air" was necessary for spontaneous generation. Pasteur made a flask
designed to allow air to reach the solution after being sterilized but prevented particulate
matter and microorganisms from entering, preventing spoilage of the solution.
Explain Koch's postulates. - Answer Koch's postulate is a set of criteria for proving that a given
microorganism causes a given disease.
What advantages do solid media offer for the isolation of microorganisms? - Answer When a
solid surface was incubated in air, masses of microbial cells developed, each having a
characteristic shape and color.
What is an example of a solid bacteriological medium? Liquid growth medium? - Answer
What is a pure culture? - Answer When a bacteria is isolated and grown away from other
microorganisms in laboratory culture.
Describe Griffith's transformation experiment. - Answer When the disease-causing strain (S) in
the experiment was in the presence of the strain that didn't cause disease (R), it transformed
the R strain into an S strain through genetic transfer.
