BIOL 271 MICROBIOLOGY MODULES 1-6 EXAM QUESTIONS AND
ANSWERS - 100% VERIFIED - LATEST 2026/2027 GUARANTEED
PASS (PASS GUARANTEE)
Who is considered the "Father of Microbiology"? Antonie van
Leeuwenhoek.
What did Leeuwenhoek use to observe microorganisms? A single-lens
microscope.
Who disproved spontaneous generation using swan-neck flasks? Louis
Pasteur.
What is the germ theory of disease? The theory that microorganisms cause
many diseases.
Who established Koch’s postulates? Robert Koch.
What is the first step of Koch’s postulates? The same pathogen must be
present in every sick individual.
What is a pathogen? A disease-causing microorganism.
Which domain of life lacks a true nucleus? Bacteria and Archaea.
Which domain contains organisms with a true nucleus? Eukarya.
Are viruses considered living organisms? No, because they lack cellular
structure and cannot reproduce independently.
What is the study of fungi called? Mycology.
What is the study of viruses called? Virology.
What is the study of parasites called? Parasitology.
What is the unit of measurement for most bacteria? Micrometer (µm).
,What is the unit of measurement for viruses? Nanometer (nm).
What does "resolution" mean in microscopy? The ability to distinguish two
objects as separate and distinct.
What type of microscope uses visible light and multiple lenses? Compound
light microscope.
What is the total magnification of a microscope with a 10x ocular and a
100x oil immersion lens? 1000x.
Why is oil used with the 100x lens? To prevent light refraction and increase
resolution.
What does "parfocal" mean? When a specimen is in focus with one
objective, it is nearly in focus with the others.
What type of microscopy uses electrons instead of light? Electron
microscopy.
What is the difference between TEM and SEM? TEM shows internal
structures (2D), SEM shows surface details (3D).
What is the purpose of staining in microscopy? To increase contrast
between the organism and the background.
What is a simple stain? Using a single basic dye to color the cell.
What is a differential stain? A stain that differentiates bacteria into groups
based on chemical differences.
What are the two most common differential stains? Gram stain and Acid-
fast stain.
What color are Gram-positive bacteria after staining? Purple.
What color are Gram-negative bacteria after staining? Pink/Red.
What is the primary stain in the Gram stain? Crystal violet.
What is the mordant in the Gram stain? Iodine.
What is the decolorizer in the Gram stain? Alcohol or acetone-alcohol.
What is the counterstain in the Gram stain? Safranin.
Which bacterial genus is identified using the acid-fast stain?
Mycobacterium.
, Why are acid-fast bacteria hard to stain? They have a waxy, lipid-rich cell
wall (mycolic acid).
What dye is used in the acid-fast stain? Carbol fuchsin.
What is a negative stain? A stain that colors the background, leaving the cell
clear.
Why use a negative stain? To observe cell morphology and capsule without
heat-fixing (which shrinks cells).
What is the stain used to visualize capsules? Capsule stain (often a negative
stain combined with a simple stain).
What is the stain used to visualize endospores? Endospore stain (malachite
green and safranin).
What is a flagella stain used for? To visualize the thin, delicate flagella by
building up dye layers.
What is the purpose of heat-fixing a slide? To kill the bacteria, attach them
to the slide, and increase dye uptake.
What is a chemically defined medium? A medium where the exact chemical
composition is known.
What is a complex medium? A medium whose exact chemical composition
is unknown (e.g., nutrient broth).
What is an example of a microorganism in the domain Archaea?
Extremophiles (halophiles, thermophiles).
What is a biofilm? A complex community of microorganisms embedded in
an extracellular polymeric substance (EPS).
What is normal microbiota? The microorganisms that normally reside on
or in the human body without causing disease.
What is an opportunistic pathogen? A microbe that causes disease only
when the host's defenses are compromised.
What is microbiome? The collective genetic material of all the microbes in a
specific environment.
What is the difference between a prokaryote and a eukaryote? Prokaryotes
lack a membrane-bound nucleus; eukaryotes have a true nucleus.
What is the scientific name for "golden staph"? Staphylococcus aureus.
ANSWERS - 100% VERIFIED - LATEST 2026/2027 GUARANTEED
PASS (PASS GUARANTEE)
Who is considered the "Father of Microbiology"? Antonie van
Leeuwenhoek.
What did Leeuwenhoek use to observe microorganisms? A single-lens
microscope.
Who disproved spontaneous generation using swan-neck flasks? Louis
Pasteur.
What is the germ theory of disease? The theory that microorganisms cause
many diseases.
Who established Koch’s postulates? Robert Koch.
What is the first step of Koch’s postulates? The same pathogen must be
present in every sick individual.
What is a pathogen? A disease-causing microorganism.
Which domain of life lacks a true nucleus? Bacteria and Archaea.
Which domain contains organisms with a true nucleus? Eukarya.
Are viruses considered living organisms? No, because they lack cellular
structure and cannot reproduce independently.
What is the study of fungi called? Mycology.
What is the study of viruses called? Virology.
What is the study of parasites called? Parasitology.
What is the unit of measurement for most bacteria? Micrometer (µm).
,What is the unit of measurement for viruses? Nanometer (nm).
What does "resolution" mean in microscopy? The ability to distinguish two
objects as separate and distinct.
What type of microscope uses visible light and multiple lenses? Compound
light microscope.
What is the total magnification of a microscope with a 10x ocular and a
100x oil immersion lens? 1000x.
Why is oil used with the 100x lens? To prevent light refraction and increase
resolution.
What does "parfocal" mean? When a specimen is in focus with one
objective, it is nearly in focus with the others.
What type of microscopy uses electrons instead of light? Electron
microscopy.
What is the difference between TEM and SEM? TEM shows internal
structures (2D), SEM shows surface details (3D).
What is the purpose of staining in microscopy? To increase contrast
between the organism and the background.
What is a simple stain? Using a single basic dye to color the cell.
What is a differential stain? A stain that differentiates bacteria into groups
based on chemical differences.
What are the two most common differential stains? Gram stain and Acid-
fast stain.
What color are Gram-positive bacteria after staining? Purple.
What color are Gram-negative bacteria after staining? Pink/Red.
What is the primary stain in the Gram stain? Crystal violet.
What is the mordant in the Gram stain? Iodine.
What is the decolorizer in the Gram stain? Alcohol or acetone-alcohol.
What is the counterstain in the Gram stain? Safranin.
Which bacterial genus is identified using the acid-fast stain?
Mycobacterium.
, Why are acid-fast bacteria hard to stain? They have a waxy, lipid-rich cell
wall (mycolic acid).
What dye is used in the acid-fast stain? Carbol fuchsin.
What is a negative stain? A stain that colors the background, leaving the cell
clear.
Why use a negative stain? To observe cell morphology and capsule without
heat-fixing (which shrinks cells).
What is the stain used to visualize capsules? Capsule stain (often a negative
stain combined with a simple stain).
What is the stain used to visualize endospores? Endospore stain (malachite
green and safranin).
What is a flagella stain used for? To visualize the thin, delicate flagella by
building up dye layers.
What is the purpose of heat-fixing a slide? To kill the bacteria, attach them
to the slide, and increase dye uptake.
What is a chemically defined medium? A medium where the exact chemical
composition is known.
What is a complex medium? A medium whose exact chemical composition
is unknown (e.g., nutrient broth).
What is an example of a microorganism in the domain Archaea?
Extremophiles (halophiles, thermophiles).
What is a biofilm? A complex community of microorganisms embedded in
an extracellular polymeric substance (EPS).
What is normal microbiota? The microorganisms that normally reside on
or in the human body without causing disease.
What is an opportunistic pathogen? A microbe that causes disease only
when the host's defenses are compromised.
What is microbiome? The collective genetic material of all the microbes in a
specific environment.
What is the difference between a prokaryote and a eukaryote? Prokaryotes
lack a membrane-bound nucleus; eukaryotes have a true nucleus.
What is the scientific name for "golden staph"? Staphylococcus aureus.
