MICROBIOLOGY TEST 3 EXAM
QUESTIONS AND ANSWERS GRADED A+
2025/2026
The child gut microbiota resembles the adult microbiota
A) by 1 month of age.
B) around age 3.
C) around age 15.
D) by 12 months of age. - ANS B) around age 3.
A woman mentions to her physician during a prenatal check-up that she plans to clean her
house from "top-to-bottom" before the baby arrives, and intends to protect her newborn from
as many "germs" as possible to prevent any possible infections. If you were the physician, how
would you advise this patient?
A) Too much cleanliness can be a bad thing for an infant, as the bacteria they acquire at an early
age help to "train" the immune system to correctly recognize pathogens but not attack
beneficial bacteria in the body. Attacking the "normal" bacteria and nonharmful substances can
cause too much inflammation, allergies, or asthma later in life.
B) The patient's plan is a good one. You never know when the infant might encounter a serious
pathogen. Since infants do not have a well-developed immune system yet, pathogens can be
very dangerous. She should disinfect all surfaces in her home daily.
C) Her plan is a good one, - ANS A) Too much cleanliness can be a bad thing for an infant, as
the bacteria they acquire at an early age help to "train" the immune system to correctly
recognize pathogens but not attack beneficial bacteria in the body. Attacking the "normal"
bacteria and nonharmful substances can cause too much inflammation, allergies, or asthma
later in life.
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,The human oral microbiota consists of
A) monoculture biofilms on tooth surfaces.
B) a small group of phylogenetically related aerobic microorganisms.
C) the same phyla that are found in the human gut.
D) diverse aerobic and anaerobic microorganisms. - ANS D) diverse aerobic and anaerobic
microorganisms.
Obligate anaerobes are likely to be found in the __________.
A) urogenital tract
B) mouth
C) colon
D) nasal cavity - ANS C) colon
Which of the following is NOT a function of the human gut microbiome?
A) maturation of the gastrointestinal tract
B) iron and trace metal absorption
C) production of volatile fatty acids from polysaccharides
D) production of essential amino acids and vitamins - ANS B) iron and trace metal absorption
The presence of microbes in the bladder is __________.
A) more likely to occur in men than women
B) likely to lead to a UTI
C) used to prime the immune response
D) normal - ANS B) likely to lead to a UTI
Which of the following is NOT true of human gut microbes?
A) They help catabolize polysaccharides.
B) They are involved in the "maturing" of the digestive tract.
C) They produce and excrete amino acids.
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,D) The population size is low, but the diversity is high. - ANS D) The population size is low, but
the diversity is high.
Normal microbiota helps to ________ colonization of pathogenic organisms.
A) promote
B) maintain
C) accelerate
D) prevent - ANS D) prevent
Which of the following environmental and host factors influence the composition of the
resident microbiota on the skin?
A) personal hygiene
B) weather
C) age
D) age, personal hygiene, and weather - ANS D) age, personal hygiene, and weather
Considering that they require an oxygen-free environment, how do obligate anaerobes survive
in the human body?
A) They live inside of organelles, such as peroxisomes.
B) They are able to use enzymes to convert reactive oxygen species to harmless molecules.
C) They are able to survive in places where aerobic organisms quickly use the available oxygen.
They can also survive in areas with impaired blood flow (reducing oxygen availability).
D) Obligate anaerobes are unable to survive in the human body. - ANS C) They are able to
survive in places where aerobic organisms quickly use the available oxygen. They can also
survive in areas with impaired blood flow (reducing oxygen availability).
Based upon microbiome projects, the most dominant microbial species in sebaceous gland
system is
A) Propionibacterium species.
B) Streptococcus species.
C) Staphylococcus species.
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, D) Corynebacterium species. - ANS A) Propionibacterium species.
Clostridium difficile infections most often occur
A) following a dietary change.
B) following antibiotic treatment.
C) following a fecal transplant.
D) following the use of a new probiotic. - ANS B) following antibiotic treatment.
The male urogenital tract is generally sterile except for the distal portion of the urethra.
True OR False - ANS True
The most heavily colonized human organ by bacteria is the ________, containing 1011-1012
bacterial cells per gram.
A) large intestine
B) small intestine
C) mouth
D) skin - ANS A) large intestine
Which of the following is NOT a major question in the Human Microbiome Project?
A) Do differences in the human microbiome correlate with differences in human health?
B) Is there a correlation between microbial population structure and host genotype?
C) How can we reduce the number of microbes on the human body?
D) Are differences in the relative abundance of different bacteria important? - ANS C) How
can we reduce the number of microbes on the human body?
The human microbiome contains all
A) organisms present in and on the body.
B) organisms within the digestive system.
C) organisms present on the skin.
4 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
QUESTIONS AND ANSWERS GRADED A+
2025/2026
The child gut microbiota resembles the adult microbiota
A) by 1 month of age.
B) around age 3.
C) around age 15.
D) by 12 months of age. - ANS B) around age 3.
A woman mentions to her physician during a prenatal check-up that she plans to clean her
house from "top-to-bottom" before the baby arrives, and intends to protect her newborn from
as many "germs" as possible to prevent any possible infections. If you were the physician, how
would you advise this patient?
A) Too much cleanliness can be a bad thing for an infant, as the bacteria they acquire at an early
age help to "train" the immune system to correctly recognize pathogens but not attack
beneficial bacteria in the body. Attacking the "normal" bacteria and nonharmful substances can
cause too much inflammation, allergies, or asthma later in life.
B) The patient's plan is a good one. You never know when the infant might encounter a serious
pathogen. Since infants do not have a well-developed immune system yet, pathogens can be
very dangerous. She should disinfect all surfaces in her home daily.
C) Her plan is a good one, - ANS A) Too much cleanliness can be a bad thing for an infant, as
the bacteria they acquire at an early age help to "train" the immune system to correctly
recognize pathogens but not attack beneficial bacteria in the body. Attacking the "normal"
bacteria and nonharmful substances can cause too much inflammation, allergies, or asthma
later in life.
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,The human oral microbiota consists of
A) monoculture biofilms on tooth surfaces.
B) a small group of phylogenetically related aerobic microorganisms.
C) the same phyla that are found in the human gut.
D) diverse aerobic and anaerobic microorganisms. - ANS D) diverse aerobic and anaerobic
microorganisms.
Obligate anaerobes are likely to be found in the __________.
A) urogenital tract
B) mouth
C) colon
D) nasal cavity - ANS C) colon
Which of the following is NOT a function of the human gut microbiome?
A) maturation of the gastrointestinal tract
B) iron and trace metal absorption
C) production of volatile fatty acids from polysaccharides
D) production of essential amino acids and vitamins - ANS B) iron and trace metal absorption
The presence of microbes in the bladder is __________.
A) more likely to occur in men than women
B) likely to lead to a UTI
C) used to prime the immune response
D) normal - ANS B) likely to lead to a UTI
Which of the following is NOT true of human gut microbes?
A) They help catabolize polysaccharides.
B) They are involved in the "maturing" of the digestive tract.
C) They produce and excrete amino acids.
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,D) The population size is low, but the diversity is high. - ANS D) The population size is low, but
the diversity is high.
Normal microbiota helps to ________ colonization of pathogenic organisms.
A) promote
B) maintain
C) accelerate
D) prevent - ANS D) prevent
Which of the following environmental and host factors influence the composition of the
resident microbiota on the skin?
A) personal hygiene
B) weather
C) age
D) age, personal hygiene, and weather - ANS D) age, personal hygiene, and weather
Considering that they require an oxygen-free environment, how do obligate anaerobes survive
in the human body?
A) They live inside of organelles, such as peroxisomes.
B) They are able to use enzymes to convert reactive oxygen species to harmless molecules.
C) They are able to survive in places where aerobic organisms quickly use the available oxygen.
They can also survive in areas with impaired blood flow (reducing oxygen availability).
D) Obligate anaerobes are unable to survive in the human body. - ANS C) They are able to
survive in places where aerobic organisms quickly use the available oxygen. They can also
survive in areas with impaired blood flow (reducing oxygen availability).
Based upon microbiome projects, the most dominant microbial species in sebaceous gland
system is
A) Propionibacterium species.
B) Streptococcus species.
C) Staphylococcus species.
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, D) Corynebacterium species. - ANS A) Propionibacterium species.
Clostridium difficile infections most often occur
A) following a dietary change.
B) following antibiotic treatment.
C) following a fecal transplant.
D) following the use of a new probiotic. - ANS B) following antibiotic treatment.
The male urogenital tract is generally sterile except for the distal portion of the urethra.
True OR False - ANS True
The most heavily colonized human organ by bacteria is the ________, containing 1011-1012
bacterial cells per gram.
A) large intestine
B) small intestine
C) mouth
D) skin - ANS A) large intestine
Which of the following is NOT a major question in the Human Microbiome Project?
A) Do differences in the human microbiome correlate with differences in human health?
B) Is there a correlation between microbial population structure and host genotype?
C) How can we reduce the number of microbes on the human body?
D) Are differences in the relative abundance of different bacteria important? - ANS C) How
can we reduce the number of microbes on the human body?
The human microbiome contains all
A) organisms present in and on the body.
B) organisms within the digestive system.
C) organisms present on the skin.
4 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
