StraighterLine
LANIF · ORCIM
◆ ◆
S Online General Education & Science Courses
EST. 2008
COLLEGE STARTS HERE
StraighterLine Microbiology Final Exam Study Set
CO M P R E H E N S I V E M I C R O B I O LO G Y E X A M I N AT I O N — 8 5 Q U E ST I O N S
INSTITUTION StraighterLine COURSE CODE BIO 250
PROGRAM General Microbiology — ACADEMIC YEAR
Undergraduate
EXAM TITLE StraighterLine Microbiology Final TOTAL QUESTIONS 85 Questions
Exam Study Set
COURSE TITLE General Microbiology FORMAT Multiple Choice — Select the
Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question unless otherwise instructed.
▸ Microbial physiology, genetics, taxonomy, metabolism, and host-pathogen interactions are all testable
content.
▸ Laboratory techniques, biochemical pathways, and antimicrobial mechanisms are emphasized
throughout.
▸ Correct answers and detailed rationales appear below each question for comprehensive study review.
▸ All content reflects current foundational microbiology curricula and evidence-based microbiological
principles.
, SECTION I — MICROBIOLOGY: FOUNDATIONS THROUGH
Questions 1 – 85
ADVANCED CONCEPTS
1. The specimen preparation technique that is best for viewing cell motility is the ______.
A. Fixed, stained smear
B. Gram stain
C. Hanging drop
D. Flagellar stain
CORRECT ANSWER C — Hanging drop
RATIONALE The hanging drop technique suspends live, unstained microorganisms in a drop
of liquid on a coverslip inverted over a depression slide, allowing direct
observation of true motility (directional movement through liquid) versus
Brownian motion (random vibration). Because the organisms remain alive and
unstained, their flagellar movement is preserved. Fixed, stained smears kill and
immobilize cells; flagellar stains show flagella but not live motion; Gram staining
involves heat fixation which destroys motility.
2. Once a mother has been sensitized to the Rh factor, which statement is correct?
A. She can be given RhoGAM in future pregnancies to prevent hemolytic disease of the
newborn
B. All other Rh+ fetuses are at risk
C. Only future Rh- fetuses are at risk
D. She can never again have a low risk pregnancy
CORRECT ANSWER B — All other Rh+ fetuses are at risk
RATIONALE Once an Rh-negative mother has been sensitized to the Rh (D) antigen — meaning
she has produced anti-Rh IgG antibodies from a prior Rh+ pregnancy, transfusion,
or sensitizing event — all subsequent Rh+ fetuses are at risk for hemolytic disease
of the fetus and newborn. Maternal IgG crosses the placenta and destroys fetal
Rh+ erythrocytes. RhoGAM (Rh immune globulin) must be given BEFORE
sensitization occurs; it cannot reverse existing sensitization. Rh- fetuses are not at
risk because they lack the D antigen.
,3. Eukaryotic chromosomes differ from bacterial chromosomes because only eukaryotes
have which characteristic(s)?
A. Histone proteins
B. Chromosomes in a nucleus
C. Elongated, not circular, chromosomes
D. All of the choices are correct
CORRECT ANSWER D — All of the choices are correct
RATIONALE Eukaryotic chromosomes differ from bacterial chromosomes in all listed ways: (1)
Eukaryotic DNA is wrapped around histone proteins forming nucleosomes, while
bacterial DNA is associated with non-histone proteins; (2) Eukaryotic
chromosomes are enclosed within a membrane-bound nucleus, whereas
bacterial DNA resides in a nucleoid region; (3) Eukaryotic chromosomes are linear
and multiple, while bacterial chromosomes are typically a single circular
molecule (with some exceptions). All three distinctions are correct.
4. Which of the following groups of microorganisms is not found among the normal gut
microbiota?
A. Firmicutes (Streptococcus, Staphylococcus, Clostridium, Bacillus)
B. Enterics (Escherichia, Enterobacter)
C. Spirilla (Leptospira, Borrelia)
D. Protozoa (Entamoeba, Trichomonas)
CORRECT ANSWER C — Spirilla (Leptospira, Borrelia)
RATIONALE Spirilla — including Leptospira (causes leptospirosis) and Borrelia (causes Lyme
disease and relapsing fever) — are pathogenic spirochetes not found among the
normal gut microbiota. The healthy gut microbiome is dominated by Firmicutes,
Bacteroidetes, Actinobacteria, and Proteobacteria (including enterics like
Escherichia). Some protozoa (Entamoeba coli, Trichomonas hominis) can be
commensal gut inhabitants. Leptospira and Borrelia are acquired through
environmental exposure or arthropod vectors, not gut colonization.
, 5. Termites are insects that require the protozoan Trichonympha in their gut to synthesize
the enzyme cellulase to degrade the cellulose in wood. The protozoan uses the end
products of the cellulose breakdown (glucose). This is a(n) ______ relationship.
A. Commensalistic
B. Mutualistic
C. Parasitic
D. Antagonistic
CORRECT ANSWER B — Mutualistic
RATIONALE This is a classic example of mutualism — both organisms benefit from the
relationship. The termite gains the ability to digest cellulose (which it cannot do
alone), obtaining energy from wood; Trichonympha receives a protected
anaerobic habitat within the termite gut and a steady supply of partially digested
cellulose and glucose end products. Neither organism can survive without the
other. Commensalism would mean one benefits without affecting the other;
parasitism involves harm to the host.
6. Which of the following is a characteristic of Histoplasma capsulatum?
A. It grows in moist soil, rich in nitrogen from bird and bat droppings
B. It is a protozoan
C. It is a dermatophyte
D. It grows in dry, arid soil
CORRECT ANSWER A — It grows in moist soil, rich in nitrogen from bird and bat droppings
RATIONALE Histoplasma capsulatum is a dimorphic fungus that thrives as a mold in moist soil
enriched with nitrogen from bird and bat guano — environments such as chicken
coops, caves with bat colonies, and starling roosts. In the soil (25°C), it produces
infectious microconidia; when inhaled into the warm human lung (37°C), it
converts to the pathogenic yeast form. It is not a protozoan or dermatophyte, and
it requires nitrogen-rich, moist conditions — not dry, arid soil. The Ohio and
Mississippi River valleys are endemic regions.
LANIF · ORCIM
◆ ◆
S Online General Education & Science Courses
EST. 2008
COLLEGE STARTS HERE
StraighterLine Microbiology Final Exam Study Set
CO M P R E H E N S I V E M I C R O B I O LO G Y E X A M I N AT I O N — 8 5 Q U E ST I O N S
INSTITUTION StraighterLine COURSE CODE BIO 250
PROGRAM General Microbiology — ACADEMIC YEAR
Undergraduate
EXAM TITLE StraighterLine Microbiology Final TOTAL QUESTIONS 85 Questions
Exam Study Set
COURSE TITLE General Microbiology FORMAT Multiple Choice — Select the
Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question unless otherwise instructed.
▸ Microbial physiology, genetics, taxonomy, metabolism, and host-pathogen interactions are all testable
content.
▸ Laboratory techniques, biochemical pathways, and antimicrobial mechanisms are emphasized
throughout.
▸ Correct answers and detailed rationales appear below each question for comprehensive study review.
▸ All content reflects current foundational microbiology curricula and evidence-based microbiological
principles.
, SECTION I — MICROBIOLOGY: FOUNDATIONS THROUGH
Questions 1 – 85
ADVANCED CONCEPTS
1. The specimen preparation technique that is best for viewing cell motility is the ______.
A. Fixed, stained smear
B. Gram stain
C. Hanging drop
D. Flagellar stain
CORRECT ANSWER C — Hanging drop
RATIONALE The hanging drop technique suspends live, unstained microorganisms in a drop
of liquid on a coverslip inverted over a depression slide, allowing direct
observation of true motility (directional movement through liquid) versus
Brownian motion (random vibration). Because the organisms remain alive and
unstained, their flagellar movement is preserved. Fixed, stained smears kill and
immobilize cells; flagellar stains show flagella but not live motion; Gram staining
involves heat fixation which destroys motility.
2. Once a mother has been sensitized to the Rh factor, which statement is correct?
A. She can be given RhoGAM in future pregnancies to prevent hemolytic disease of the
newborn
B. All other Rh+ fetuses are at risk
C. Only future Rh- fetuses are at risk
D. She can never again have a low risk pregnancy
CORRECT ANSWER B — All other Rh+ fetuses are at risk
RATIONALE Once an Rh-negative mother has been sensitized to the Rh (D) antigen — meaning
she has produced anti-Rh IgG antibodies from a prior Rh+ pregnancy, transfusion,
or sensitizing event — all subsequent Rh+ fetuses are at risk for hemolytic disease
of the fetus and newborn. Maternal IgG crosses the placenta and destroys fetal
Rh+ erythrocytes. RhoGAM (Rh immune globulin) must be given BEFORE
sensitization occurs; it cannot reverse existing sensitization. Rh- fetuses are not at
risk because they lack the D antigen.
,3. Eukaryotic chromosomes differ from bacterial chromosomes because only eukaryotes
have which characteristic(s)?
A. Histone proteins
B. Chromosomes in a nucleus
C. Elongated, not circular, chromosomes
D. All of the choices are correct
CORRECT ANSWER D — All of the choices are correct
RATIONALE Eukaryotic chromosomes differ from bacterial chromosomes in all listed ways: (1)
Eukaryotic DNA is wrapped around histone proteins forming nucleosomes, while
bacterial DNA is associated with non-histone proteins; (2) Eukaryotic
chromosomes are enclosed within a membrane-bound nucleus, whereas
bacterial DNA resides in a nucleoid region; (3) Eukaryotic chromosomes are linear
and multiple, while bacterial chromosomes are typically a single circular
molecule (with some exceptions). All three distinctions are correct.
4. Which of the following groups of microorganisms is not found among the normal gut
microbiota?
A. Firmicutes (Streptococcus, Staphylococcus, Clostridium, Bacillus)
B. Enterics (Escherichia, Enterobacter)
C. Spirilla (Leptospira, Borrelia)
D. Protozoa (Entamoeba, Trichomonas)
CORRECT ANSWER C — Spirilla (Leptospira, Borrelia)
RATIONALE Spirilla — including Leptospira (causes leptospirosis) and Borrelia (causes Lyme
disease and relapsing fever) — are pathogenic spirochetes not found among the
normal gut microbiota. The healthy gut microbiome is dominated by Firmicutes,
Bacteroidetes, Actinobacteria, and Proteobacteria (including enterics like
Escherichia). Some protozoa (Entamoeba coli, Trichomonas hominis) can be
commensal gut inhabitants. Leptospira and Borrelia are acquired through
environmental exposure or arthropod vectors, not gut colonization.
, 5. Termites are insects that require the protozoan Trichonympha in their gut to synthesize
the enzyme cellulase to degrade the cellulose in wood. The protozoan uses the end
products of the cellulose breakdown (glucose). This is a(n) ______ relationship.
A. Commensalistic
B. Mutualistic
C. Parasitic
D. Antagonistic
CORRECT ANSWER B — Mutualistic
RATIONALE This is a classic example of mutualism — both organisms benefit from the
relationship. The termite gains the ability to digest cellulose (which it cannot do
alone), obtaining energy from wood; Trichonympha receives a protected
anaerobic habitat within the termite gut and a steady supply of partially digested
cellulose and glucose end products. Neither organism can survive without the
other. Commensalism would mean one benefits without affecting the other;
parasitism involves harm to the host.
6. Which of the following is a characteristic of Histoplasma capsulatum?
A. It grows in moist soil, rich in nitrogen from bird and bat droppings
B. It is a protozoan
C. It is a dermatophyte
D. It grows in dry, arid soil
CORRECT ANSWER A — It grows in moist soil, rich in nitrogen from bird and bat droppings
RATIONALE Histoplasma capsulatum is a dimorphic fungus that thrives as a mold in moist soil
enriched with nitrogen from bird and bat guano — environments such as chicken
coops, caves with bat colonies, and starling roosts. In the soil (25°C), it produces
infectious microconidia; when inhaled into the warm human lung (37°C), it
converts to the pathogenic yeast form. It is not a protozoan or dermatophyte, and
it requires nitrogen-rich, moist conditions — not dry, arid soil. The Ohio and
Mississippi River valleys are endemic regions.
