1
OPENSTAX MICROBIOLOGY TEST BANK Chapters 1-
5 | 2026 Edition | Original Practice Questions
CHAPTER 1: AN INVISIBLE WORLD
The History and Scope of Microbiology
MULTIPLE CHOICE
1. Which scientist is credited with the first observation of microorganisms using
a single-lens microscope that he designed?
A. Robert Hooke
B. Louis Pasteur
C. Antonie van Leeuwenhoek
D. Robert Koch
Answer :C
Rationale: Antonie van Leeuwenhoek (1632-1723) was a Dutch cloth merchant
who ground his own lenses and created simple microscopes capable of
magnifying up to 300x. He was the first to observe and describe "animalcules"
(bacteria and protozoa) from dental plaque, pond water, and other sources.
Robert Hooke (A) coined the term "cell" after observing cork under a compound
microscope. Pasteur (B) disproved spontaneous generation. Koch (D) established
the germ theory of disease.
2. Louis Pasteur's experiments using swan-necked flasks demonstrated that:
A. Microorganisms cause disease
B. Microorganisms are present in the air and can contaminate sterile solutions,
but they do not spontaneously generate
C. All microorganisms require oxygen
D. Heat is ineffective at killing microorganisms
Answer :B
pg. 1
,2
Rationale: Pasteur's swan-neck flask experiment (1861) definitively disproved the
theory of spontaneous generation. He showed that boiled broth remained sterile
indefinitely in swan-neck flasks (which allowed air in but trapped airborne
microorganisms in the curve of the neck). When the neck was broken, microbial
growth occurred. This demonstrated that microorganisms come from existing
microorganisms, not spontaneous generation.
3. Robert Koch established a series of postulates to:
A. Classify all known bacteria
B. Identify the causative agent of a specific disease
C. Develop vaccines for viral diseases
D. Create pure cultures of fungi
Answer :B
Rationale: Koch's postulates (1884) provide a framework for establishing that a
specific microorganism causes a specific disease. The four postulates are: (1) The
organism must be present in every case of the disease, (2) The organism must be
isolated and grown in pure culture, (3) The pure culture must cause the disease
when inoculated into a healthy host, (4) The organism must be re-isolated from
the experimentally infected host.
4. The scientist who developed the first vaccine against smallpox using cowpox
virus was:
A. Louis Pasteur
B. Edward Jenner
C. Joseph Lister
D. Alexander Fleming
Answer :B
Rationale: Edward Jenner (1796) observed that milkmaids who had contracted
cowpox (a mild disease) were immune to smallpox. He inoculated a boy with
material from a cowpox lesion and later challenged him with smallpox—the boy
did not develop disease. This was the world's first vaccine. Pasteur (A) later
pg. 2
,3
developed vaccines for rabies and anthrax. Lister (C) introduced antiseptic
surgery. Fleming (D) discovered penicillin.
5. Which scientist is credited with discovering the antibiotic penicillin?
A. Selman Waksman
B. Paul Ehrlich
C. Alexander Fleming
D. Gerhard Domagk
Answer :C
Rationale: Alexander Fleming (1928) accidentally discovered penicillin when a
mold (Penicillium notatum) contaminated his Staphylococcus cultures and
inhibited bacterial growth. This discovery revolutionized medicine. Waksman (A)
discovered streptomycin. Ehrlich (B) developed the "magic bullet" concept and
discovered salvarsan for syphilis. Domagk (D) discovered sulfa drugs.
6. Joseph Lister is known for:
A. Developing the first microscope
B. Introducing antiseptic techniques in surgery using carbolic acid (phenol)
C. Discovering the structure of DNA
D. Developing the first polio vaccine
Answer :B
Rationale: Joseph Lister (1867) introduced antiseptic surgery after learning of
Pasteur's work on microorganisms. He used carbolic acid (phenol) to clean
surgical instruments, wounds, and the surgical environment, dramatically
reducing post-operative infections. This was a major advancement in medical
practice.
7. The term "microbiota" refers to:
A. All microorganisms that cause disease
B. The collection of microorganisms (bacteria, archaea, fungi, protists, viruses)
pg. 3
, 4
that live in and on the human body
C. Only bacteria found in the gut
D. Microorganisms found exclusively in soil
Answer :B
Rationale: The human microbiota (also called the microbiome) is the complete
collection of microorganisms (bacteria, archaea, fungi, protists, viruses) that
reside in and on the human body. These microorganisms outnumber human cells
and play essential roles in digestion, immunity, vitamin synthesis, and protection
against pathogens. The term "pathogen" specifically refers to disease-causing
organisms.
8. Which of the following correctly lists the hierarchy of biological classification
from most inclusive to most specific?
A. Kingdom → Phylum → Class → Order → Family → Genus → Species
B. Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
C. Species → Genus → Family → Order → Class → Phylum → Kingdom → Domain
D. Domain → Phylum → Kingdom → Class → Order → Family → Genus → Species
Answer :B
Rationale: The taxonomic hierarchy (developed by Carl Linnaeus) from most
inclusive to most specific is: Domain → Kingdom → Phylum → Class → Order →
Family → Genus → Species. The three domains (Woese and Fox, 1977) are
Bacteria, Archaea, and Eukarya. The mnemonic "Dear King Philip Came Over For
Good Soup" is often used to remember this sequence.
9. The binomial nomenclature system for naming organisms uses:
A. Kingdom and Phylum
B. Genus and Species
C. Family and Order
D. Class and Domain
Answer :B
pg. 4
OPENSTAX MICROBIOLOGY TEST BANK Chapters 1-
5 | 2026 Edition | Original Practice Questions
CHAPTER 1: AN INVISIBLE WORLD
The History and Scope of Microbiology
MULTIPLE CHOICE
1. Which scientist is credited with the first observation of microorganisms using
a single-lens microscope that he designed?
A. Robert Hooke
B. Louis Pasteur
C. Antonie van Leeuwenhoek
D. Robert Koch
Answer :C
Rationale: Antonie van Leeuwenhoek (1632-1723) was a Dutch cloth merchant
who ground his own lenses and created simple microscopes capable of
magnifying up to 300x. He was the first to observe and describe "animalcules"
(bacteria and protozoa) from dental plaque, pond water, and other sources.
Robert Hooke (A) coined the term "cell" after observing cork under a compound
microscope. Pasteur (B) disproved spontaneous generation. Koch (D) established
the germ theory of disease.
2. Louis Pasteur's experiments using swan-necked flasks demonstrated that:
A. Microorganisms cause disease
B. Microorganisms are present in the air and can contaminate sterile solutions,
but they do not spontaneously generate
C. All microorganisms require oxygen
D. Heat is ineffective at killing microorganisms
Answer :B
pg. 1
,2
Rationale: Pasteur's swan-neck flask experiment (1861) definitively disproved the
theory of spontaneous generation. He showed that boiled broth remained sterile
indefinitely in swan-neck flasks (which allowed air in but trapped airborne
microorganisms in the curve of the neck). When the neck was broken, microbial
growth occurred. This demonstrated that microorganisms come from existing
microorganisms, not spontaneous generation.
3. Robert Koch established a series of postulates to:
A. Classify all known bacteria
B. Identify the causative agent of a specific disease
C. Develop vaccines for viral diseases
D. Create pure cultures of fungi
Answer :B
Rationale: Koch's postulates (1884) provide a framework for establishing that a
specific microorganism causes a specific disease. The four postulates are: (1) The
organism must be present in every case of the disease, (2) The organism must be
isolated and grown in pure culture, (3) The pure culture must cause the disease
when inoculated into a healthy host, (4) The organism must be re-isolated from
the experimentally infected host.
4. The scientist who developed the first vaccine against smallpox using cowpox
virus was:
A. Louis Pasteur
B. Edward Jenner
C. Joseph Lister
D. Alexander Fleming
Answer :B
Rationale: Edward Jenner (1796) observed that milkmaids who had contracted
cowpox (a mild disease) were immune to smallpox. He inoculated a boy with
material from a cowpox lesion and later challenged him with smallpox—the boy
did not develop disease. This was the world's first vaccine. Pasteur (A) later
pg. 2
,3
developed vaccines for rabies and anthrax. Lister (C) introduced antiseptic
surgery. Fleming (D) discovered penicillin.
5. Which scientist is credited with discovering the antibiotic penicillin?
A. Selman Waksman
B. Paul Ehrlich
C. Alexander Fleming
D. Gerhard Domagk
Answer :C
Rationale: Alexander Fleming (1928) accidentally discovered penicillin when a
mold (Penicillium notatum) contaminated his Staphylococcus cultures and
inhibited bacterial growth. This discovery revolutionized medicine. Waksman (A)
discovered streptomycin. Ehrlich (B) developed the "magic bullet" concept and
discovered salvarsan for syphilis. Domagk (D) discovered sulfa drugs.
6. Joseph Lister is known for:
A. Developing the first microscope
B. Introducing antiseptic techniques in surgery using carbolic acid (phenol)
C. Discovering the structure of DNA
D. Developing the first polio vaccine
Answer :B
Rationale: Joseph Lister (1867) introduced antiseptic surgery after learning of
Pasteur's work on microorganisms. He used carbolic acid (phenol) to clean
surgical instruments, wounds, and the surgical environment, dramatically
reducing post-operative infections. This was a major advancement in medical
practice.
7. The term "microbiota" refers to:
A. All microorganisms that cause disease
B. The collection of microorganisms (bacteria, archaea, fungi, protists, viruses)
pg. 3
, 4
that live in and on the human body
C. Only bacteria found in the gut
D. Microorganisms found exclusively in soil
Answer :B
Rationale: The human microbiota (also called the microbiome) is the complete
collection of microorganisms (bacteria, archaea, fungi, protists, viruses) that
reside in and on the human body. These microorganisms outnumber human cells
and play essential roles in digestion, immunity, vitamin synthesis, and protection
against pathogens. The term "pathogen" specifically refers to disease-causing
organisms.
8. Which of the following correctly lists the hierarchy of biological classification
from most inclusive to most specific?
A. Kingdom → Phylum → Class → Order → Family → Genus → Species
B. Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
C. Species → Genus → Family → Order → Class → Phylum → Kingdom → Domain
D. Domain → Phylum → Kingdom → Class → Order → Family → Genus → Species
Answer :B
Rationale: The taxonomic hierarchy (developed by Carl Linnaeus) from most
inclusive to most specific is: Domain → Kingdom → Phylum → Class → Order →
Family → Genus → Species. The three domains (Woese and Fox, 1977) are
Bacteria, Archaea, and Eukarya. The mnemonic "Dear King Philip Came Over For
Good Soup" is often used to remember this sequence.
9. The binomial nomenclature system for naming organisms uses:
A. Kingdom and Phylum
B. Genus and Species
C. Family and Order
D. Class and Domain
Answer :B
pg. 4
