,CONTENT
Chapter 1 Microbiology—The Science
Chapter 2 Viewing the Microbial World
Chapter 3 Cell Structure and Taxonomy
Chapter 4 Acellular and Prokaryotic Microbes
Chapter 5 Eukaryotic Microbes
Chapter 6 The Biochemical Basis of Life
Chapter 7 Microbial Physiology and Genetics
Chapter 8 Controlling Microbial Growth In Vitro
Chapter 9 Inhibiting the Growth of Pathogens In Vivo using Antimicrobial Agents
Chapter 10 Microbial Ecology and Microbial Biotechnology
Chapter 11 Epidemiology and Public Health
Chapter 12 Health Care Epidemiology and Infection Prevention and Control
Chapter 13 Diagnosing Infectious Diseases
Chapter 14 Pathogenesis of Infectious Diseases
Chapter 15 Nonspecific Host Defense Mechanisms
Chapter 16 Specific Host Defense Mechanisms: An Introduction to Immunology
Chapter 17 Overview of Human Infectious Diseases
Chapter 18 Viral Infections of Humans
Chapter 19 Bacterial Infections of Humans
Chapter 20 Fungal Infections of Humans
Chapter 21 Parasitic Infections of Humans
,Chapter 1 — Microbiology: The Science
Topic: Microbiology: The Science — importance of microbes in health, disease,
environment, biotechnology; historical figures and germ theory.
1. Louis Pasteur’s swan-neck flask experiments are considered decisive evidence
against spontaneous generation because they showed that:
A. Heat alone killed all microbes in the broth and prevented recontamination.
B. Sterile broth remained free of microbial growth when exposed to air but
protected from particulate matter.
C. Microbes spontaneously arose in broth after cooling because of chemical
decomposition.
D. Only air that passed through a cotton plug could carry microbes into broth.
Answer:B
Rationale: Pasteur used specially shaped (swan-neck) flasks: he boiled broth to
sterilize it, then let it cool. Air could still enter the flask, but airborne particulate
matter settled in the curve and did not reach the broth; no growth occurred. This
demonstrated that microbes come from particulate contamination (preexisting
organisms) rather than spontaneous generation. Option A is incomplete/incorrect
— heat sterilizes but the key control was exclusion of particles while allowing air.
C contradicts the experiment outcome. D misattributes a cotton plug mechanism;
although cotton plugs were used in other experiments, the critical observation in
the swan-neck experiment was exclusion of particulates, not filtration through
cotton.
Key words: Pasteur, swan-neck flask, spontaneous generation, sterilization,
particulate contamination.
2. Which of the following is the best statement describing a major limitation of
Koch’s original postulates?
A. They require isolated agents to be proven transmissible by aerosol.
B. They cannot be fulfilled for diseases caused by nonculturable or asymptomatic
agents.
C. They assume all diseases are caused by viruses.
D. They were formulated before microscopy existed and therefore are obsolete.
,Answer:B
Rationale: Koch’s postulates assume the pathogen can be isolated, cultured, and
will cause disease when introduced into a susceptible host. This fails for many
pathogens that are nonculturable in vitro (e.g., certain bacteria, obligate
intracellular agents), for pathogens that require a specific host or microbiome
context, and for asymptomatic carriers where disease doesn't develop in every host.
A is false — postulates do not mandate aerosol transmission. C is incorrect;
postulates were designed for bacteria. D is false — microscopy existed in some
form, and the postulates remain conceptually useful but have known limits; they
are not obsolete but have been expanded (e.g., molecular Koch’s postulates).
Key words: Koch’s postulates, nonculturable organisms, asymptomatic carriers,
limitations.
3. Joseph Lister’s introduction of carbolic acid in surgery resulted primarily from
the idea that:
A. Airborne miasmas were the sole cause of post-operative infections.
B. Applying a chemical antiseptic to wounds and instruments could reduce
microbial contamination and sepsis.
C. Sterile operating rooms could be achieved by filtering the air through charcoal.
D. Systemic antibiotics were available to treat surgical infections if they occurred.
Answer:B
Rationale: Lister adopted the germ theory and reasoned that applying an antiseptic
(carbolic acid, phenol) to surgical wounds and instruments would destroy microbes
and reduce post-operative sepsis and mortality. His antiseptic practices preceded
antibiotics (D is anachronistic). A is incorrect because Lister rejected miasma and
favored contact microbes as causes of infection. C is not historically accurate —
air filtration by charcoal was not his solution. Lister’s practices laid groundwork
for antisepsis and later aseptic techniques.
Key words: Lister, antisepsis, carbolic acid, germ theory, surgical infection.
4. The human gut microbiome confers colonization resistance against enteric
pathogens primarily by:
A. Producing high levels of systemic antibodies that neutralize invaders before
they reach the gut.
B. Occupying ecological niches and producing antimicrobial compounds that limit
,pathogen establishment.
C. Raising internal body temperature to levels that kill invading bacteria.
D. Preventing all horizontal gene transfer between microbes.
Answer:B
Rationale: Colonization resistance is mediated by resident microbiota occupying
attachment sites and metabolic niches, competing for nutrients, and synthesizing
bacteriocins and other antimicrobials; they also modulate local immunity. A is
incorrect — systemic antibodies are not the primary mechanism for gut
colonization resistance. C (fever) is a systemic host response, not a microbiome
function. D is false — horizontal gene transfer can and does occur in the gut and
contributes to antibiotic resistance spread. Understanding colonization resistance is
key to appreciating beneficial roles of microbes in health.
Key words: microbiome, colonization resistance, competition, bacteriocins, niche
occupancy.
5. Which example best illustrates a microbe’s pivotal role in a global
biogeochemical cycle?
A. Candida spp. fermenting sugars to produce ethanol during baking.
B. Rhizobium spp. fixing atmospheric nitrogen into ammonia for plant use.
C. Staphylococcus aureus causing wound infections in hospitals.
D. Influenza virus evolving antigenic drift in seasonal epidemics.
Answer:B
Rationale: Rhizobium forms symbiotic relationships with legumes and fixes
atmospheric N₂ into bioavailable ammonia, a central process in the nitrogen cycle
that affects ecosystem productivity and agriculture. A is industrial/food
fermentation — important but not a global biogeochemical cycle. C and D are
clinical/epidemiological examples not related to global nutrient cycling. This
question emphasizes environmental roles of microbes beyond disease.
Key words: Rhizobium, nitrogen fixation, biogeochemical cycles, ecosystem
services.
6. When designing a recombinant protein production system for a human
therapeutic (e.g., insulin), why might scientists choose E. coli over Saccharomyces
cerevisiae?
A. E. coli can perform complex eukaryotic glycosylation required for all human
, proteins.
B. Saccharomyces grows faster and is therefore always preferred over E. coli.
C. E. coli has simpler, high-yield expression and well-characterized genetics,
though lacks eukaryotic post-translational modifications.
D. E. coli is nonpathogenic in all strains and requires no containment.
Answer:C
Rationale: E. coli is often selected for recombinant protein expression because of
rapid growth, high yields, cheap media, and a wealth of genetic tools. However, it
lacks eukaryotic post-translational modifications (e.g., glycosylation), which may
be acceptable (as with insulin, which can be produced as functional protein) or
problematic for other therapeutics. A is false — E. coli generally cannot perform
complex glycosylation. B is incorrect generalization. D is false — some strains
require containment and there are safety considerations. This question ties
biotechnology choices to microbial physiology and therapeutic requirements.
Key words: recombinant protein, E. coli, yeast, post-translational modification,
expression system.
7. Which historical development most directly led to the shift from miasma theory
to germ theory in clinical practice?
A. Discovery of penicillin and sulfonamides.
B. Microscopic observation of bacteria and experiments linking specific microbes
to specific diseases.
C. Development of X-ray imaging for internal organs.
D. Widespread use of antiseptics without understanding their mechanism.
Answer:B
Rationale: The ability to observe microbes with improved microscopy and to
experimentally link particular organisms to disease (e.g., Pasteur, Koch) provided
strong empirical evidence replacing miasma (bad air) theories. This scientific
grounding changed clinical practice — sterilization, aseptic technique, and targeted
interventions. A (antibiotics) occurred later and relied on germ theory. C is
unrelated. D is partially true historically but antiseptic use became rational and
widespread because of germ theory evidence; using antiseptics without
understanding would not have been the defining driver.
Key words: germ theory, microscopy, Pasteur, Koch, miasma.
Chapter 1 Microbiology—The Science
Chapter 2 Viewing the Microbial World
Chapter 3 Cell Structure and Taxonomy
Chapter 4 Acellular and Prokaryotic Microbes
Chapter 5 Eukaryotic Microbes
Chapter 6 The Biochemical Basis of Life
Chapter 7 Microbial Physiology and Genetics
Chapter 8 Controlling Microbial Growth In Vitro
Chapter 9 Inhibiting the Growth of Pathogens In Vivo using Antimicrobial Agents
Chapter 10 Microbial Ecology and Microbial Biotechnology
Chapter 11 Epidemiology and Public Health
Chapter 12 Health Care Epidemiology and Infection Prevention and Control
Chapter 13 Diagnosing Infectious Diseases
Chapter 14 Pathogenesis of Infectious Diseases
Chapter 15 Nonspecific Host Defense Mechanisms
Chapter 16 Specific Host Defense Mechanisms: An Introduction to Immunology
Chapter 17 Overview of Human Infectious Diseases
Chapter 18 Viral Infections of Humans
Chapter 19 Bacterial Infections of Humans
Chapter 20 Fungal Infections of Humans
Chapter 21 Parasitic Infections of Humans
,Chapter 1 — Microbiology: The Science
Topic: Microbiology: The Science — importance of microbes in health, disease,
environment, biotechnology; historical figures and germ theory.
1. Louis Pasteur’s swan-neck flask experiments are considered decisive evidence
against spontaneous generation because they showed that:
A. Heat alone killed all microbes in the broth and prevented recontamination.
B. Sterile broth remained free of microbial growth when exposed to air but
protected from particulate matter.
C. Microbes spontaneously arose in broth after cooling because of chemical
decomposition.
D. Only air that passed through a cotton plug could carry microbes into broth.
Answer:B
Rationale: Pasteur used specially shaped (swan-neck) flasks: he boiled broth to
sterilize it, then let it cool. Air could still enter the flask, but airborne particulate
matter settled in the curve and did not reach the broth; no growth occurred. This
demonstrated that microbes come from particulate contamination (preexisting
organisms) rather than spontaneous generation. Option A is incomplete/incorrect
— heat sterilizes but the key control was exclusion of particles while allowing air.
C contradicts the experiment outcome. D misattributes a cotton plug mechanism;
although cotton plugs were used in other experiments, the critical observation in
the swan-neck experiment was exclusion of particulates, not filtration through
cotton.
Key words: Pasteur, swan-neck flask, spontaneous generation, sterilization,
particulate contamination.
2. Which of the following is the best statement describing a major limitation of
Koch’s original postulates?
A. They require isolated agents to be proven transmissible by aerosol.
B. They cannot be fulfilled for diseases caused by nonculturable or asymptomatic
agents.
C. They assume all diseases are caused by viruses.
D. They were formulated before microscopy existed and therefore are obsolete.
,Answer:B
Rationale: Koch’s postulates assume the pathogen can be isolated, cultured, and
will cause disease when introduced into a susceptible host. This fails for many
pathogens that are nonculturable in vitro (e.g., certain bacteria, obligate
intracellular agents), for pathogens that require a specific host or microbiome
context, and for asymptomatic carriers where disease doesn't develop in every host.
A is false — postulates do not mandate aerosol transmission. C is incorrect;
postulates were designed for bacteria. D is false — microscopy existed in some
form, and the postulates remain conceptually useful but have known limits; they
are not obsolete but have been expanded (e.g., molecular Koch’s postulates).
Key words: Koch’s postulates, nonculturable organisms, asymptomatic carriers,
limitations.
3. Joseph Lister’s introduction of carbolic acid in surgery resulted primarily from
the idea that:
A. Airborne miasmas were the sole cause of post-operative infections.
B. Applying a chemical antiseptic to wounds and instruments could reduce
microbial contamination and sepsis.
C. Sterile operating rooms could be achieved by filtering the air through charcoal.
D. Systemic antibiotics were available to treat surgical infections if they occurred.
Answer:B
Rationale: Lister adopted the germ theory and reasoned that applying an antiseptic
(carbolic acid, phenol) to surgical wounds and instruments would destroy microbes
and reduce post-operative sepsis and mortality. His antiseptic practices preceded
antibiotics (D is anachronistic). A is incorrect because Lister rejected miasma and
favored contact microbes as causes of infection. C is not historically accurate —
air filtration by charcoal was not his solution. Lister’s practices laid groundwork
for antisepsis and later aseptic techniques.
Key words: Lister, antisepsis, carbolic acid, germ theory, surgical infection.
4. The human gut microbiome confers colonization resistance against enteric
pathogens primarily by:
A. Producing high levels of systemic antibodies that neutralize invaders before
they reach the gut.
B. Occupying ecological niches and producing antimicrobial compounds that limit
,pathogen establishment.
C. Raising internal body temperature to levels that kill invading bacteria.
D. Preventing all horizontal gene transfer between microbes.
Answer:B
Rationale: Colonization resistance is mediated by resident microbiota occupying
attachment sites and metabolic niches, competing for nutrients, and synthesizing
bacteriocins and other antimicrobials; they also modulate local immunity. A is
incorrect — systemic antibodies are not the primary mechanism for gut
colonization resistance. C (fever) is a systemic host response, not a microbiome
function. D is false — horizontal gene transfer can and does occur in the gut and
contributes to antibiotic resistance spread. Understanding colonization resistance is
key to appreciating beneficial roles of microbes in health.
Key words: microbiome, colonization resistance, competition, bacteriocins, niche
occupancy.
5. Which example best illustrates a microbe’s pivotal role in a global
biogeochemical cycle?
A. Candida spp. fermenting sugars to produce ethanol during baking.
B. Rhizobium spp. fixing atmospheric nitrogen into ammonia for plant use.
C. Staphylococcus aureus causing wound infections in hospitals.
D. Influenza virus evolving antigenic drift in seasonal epidemics.
Answer:B
Rationale: Rhizobium forms symbiotic relationships with legumes and fixes
atmospheric N₂ into bioavailable ammonia, a central process in the nitrogen cycle
that affects ecosystem productivity and agriculture. A is industrial/food
fermentation — important but not a global biogeochemical cycle. C and D are
clinical/epidemiological examples not related to global nutrient cycling. This
question emphasizes environmental roles of microbes beyond disease.
Key words: Rhizobium, nitrogen fixation, biogeochemical cycles, ecosystem
services.
6. When designing a recombinant protein production system for a human
therapeutic (e.g., insulin), why might scientists choose E. coli over Saccharomyces
cerevisiae?
A. E. coli can perform complex eukaryotic glycosylation required for all human
, proteins.
B. Saccharomyces grows faster and is therefore always preferred over E. coli.
C. E. coli has simpler, high-yield expression and well-characterized genetics,
though lacks eukaryotic post-translational modifications.
D. E. coli is nonpathogenic in all strains and requires no containment.
Answer:C
Rationale: E. coli is often selected for recombinant protein expression because of
rapid growth, high yields, cheap media, and a wealth of genetic tools. However, it
lacks eukaryotic post-translational modifications (e.g., glycosylation), which may
be acceptable (as with insulin, which can be produced as functional protein) or
problematic for other therapeutics. A is false — E. coli generally cannot perform
complex glycosylation. B is incorrect generalization. D is false — some strains
require containment and there are safety considerations. This question ties
biotechnology choices to microbial physiology and therapeutic requirements.
Key words: recombinant protein, E. coli, yeast, post-translational modification,
expression system.
7. Which historical development most directly led to the shift from miasma theory
to germ theory in clinical practice?
A. Discovery of penicillin and sulfonamides.
B. Microscopic observation of bacteria and experiments linking specific microbes
to specific diseases.
C. Development of X-ray imaging for internal organs.
D. Widespread use of antiseptics without understanding their mechanism.
Answer:B
Rationale: The ability to observe microbes with improved microscopy and to
experimentally link particular organisms to disease (e.g., Pasteur, Koch) provided
strong empirical evidence replacing miasma (bad air) theories. This scientific
grounding changed clinical practice — sterilization, aseptic technique, and targeted
interventions. A (antibiotics) occurred later and relied on germ theory. C is
unrelated. D is partially true historically but antiseptic use became rational and
widespread because of germ theory evidence; using antiseptics without
understanding would not have been the defining driver.
Key words: germ theory, microscopy, Pasteur, Koch, miasma.
