PORTAGE MICROBIOLOGY EXAM 4
QUESTIONS WITH 100% CORRECT
ANSWERS L LATEST VERSION 2025/2026.
True or False: Growth media is best suited for distinguishing between two similar species of
bacteria - ANS False. Growth media is designed to simply support (and not restrict) microbial
growth
A researcher is asked to determine which of two vials contains e coli and which contains
salmonella. Knowing both gram-negative while only one of them is capable of fermenting
lactose, which type of media would be best suited (multiple choice) - ANS Differential media
distinguishes between two, often related, microbes
A researcher is asked to determine if a sample contains Neisseria meningitides. Knowing
Neisseria meningitides is slow growing and other foreign microbes may also be present in the
culture, which type of media would be best suited? (multiple choice) - ANS Selective media
What are the requirements of a fastidious microbe? (short answer) - ANS A fastidious
microbe is an organism with complex growth requirements such that is absent it will not grow.
Enriched medias thus contain these specific and essential nutrients required for the growth of a
particular subset of microorganisms.
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, True or False: LB agar is classified as a selective, non-differential media - ANS False
What is agar used for in microbiology? (short answer) - ANS Agar is used to create a solid,
smooth surface on which microbes can grow
Alpha hemolysis (matching) - ANS Incomplete hemolytic activity
Beta hemolysis (matching) - ANS Complete hemolytic activity
Gamma hemolysis (matching) - ANS no hemolytic activity
Columbia CNA agar is most closely related to which media (multiple choice) - ANS blood agar
True or False: Chocolate agar gets its brown color from cocoa to produce an enriched media -
ANS false
True or False: Chocolate is not a component of chocolate agar plates - ANS true
A researcher is studying a strain of e coli currently growing on a MacConkey plate. However, the
researcher can't remember if e coli is gram positive or gram negative. Would a gram stain be
necessary to confirm? Why or why not? (short answer) - ANS No. A gram stain would not be
necessary, as only gram negative microbes will grown on MacConkey agar. Thus, e coli is a gram
negative microbe
In an attempt to detect the presence of the pathogenic strain of e coli O157:H7, a researcher
spread culture onto a MacConkey agar with failed results. What type of agar should they
(correctly) try next? Why? (short answer) - ANS The microbe should be plated on SMAC as it
is specifically formulated to detect O157:H7. Pathogenic e coli cannot ferment sorbitol while
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
QUESTIONS WITH 100% CORRECT
ANSWERS L LATEST VERSION 2025/2026.
True or False: Growth media is best suited for distinguishing between two similar species of
bacteria - ANS False. Growth media is designed to simply support (and not restrict) microbial
growth
A researcher is asked to determine which of two vials contains e coli and which contains
salmonella. Knowing both gram-negative while only one of them is capable of fermenting
lactose, which type of media would be best suited (multiple choice) - ANS Differential media
distinguishes between two, often related, microbes
A researcher is asked to determine if a sample contains Neisseria meningitides. Knowing
Neisseria meningitides is slow growing and other foreign microbes may also be present in the
culture, which type of media would be best suited? (multiple choice) - ANS Selective media
What are the requirements of a fastidious microbe? (short answer) - ANS A fastidious
microbe is an organism with complex growth requirements such that is absent it will not grow.
Enriched medias thus contain these specific and essential nutrients required for the growth of a
particular subset of microorganisms.
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, True or False: LB agar is classified as a selective, non-differential media - ANS False
What is agar used for in microbiology? (short answer) - ANS Agar is used to create a solid,
smooth surface on which microbes can grow
Alpha hemolysis (matching) - ANS Incomplete hemolytic activity
Beta hemolysis (matching) - ANS Complete hemolytic activity
Gamma hemolysis (matching) - ANS no hemolytic activity
Columbia CNA agar is most closely related to which media (multiple choice) - ANS blood agar
True or False: Chocolate agar gets its brown color from cocoa to produce an enriched media -
ANS false
True or False: Chocolate is not a component of chocolate agar plates - ANS true
A researcher is studying a strain of e coli currently growing on a MacConkey plate. However, the
researcher can't remember if e coli is gram positive or gram negative. Would a gram stain be
necessary to confirm? Why or why not? (short answer) - ANS No. A gram stain would not be
necessary, as only gram negative microbes will grown on MacConkey agar. Thus, e coli is a gram
negative microbe
In an attempt to detect the presence of the pathogenic strain of e coli O157:H7, a researcher
spread culture onto a MacConkey agar with failed results. What type of agar should they
(correctly) try next? Why? (short answer) - ANS The microbe should be plated on SMAC as it
is specifically formulated to detect O157:H7. Pathogenic e coli cannot ferment sorbitol while
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
