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
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.
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
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, Gamma hemolysis (matching) - ANS No hemolytic activity
Columbia CNA agar is most closely related to which media (multiple choice) - ANS CNA agar is
similar to VAP as it is also enriched with blood and allows for differentiation based on hemolytic
patterns
True or False: Chocolate agar gets its brown color from cocoa to produce an enriched media -
ANS False
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
non-pathogenic e coli can ferment both sorbitol and lactose. Therefore, colonies that ferment
can be differentiated from non-fermenters.
What is the gram status of microbes growing on eosin methylene blue agar plates? (short
answer) - ANS Gram-negative
What is the process of spreading a bacterial culture onto a petri dish? (short answer) -
ANS Plating
Mannitol salt agar will turn what color in the presence of the pathogenic strain staphylococcus
aureus? (short answer) - ANS Yellow
In order to visual individual colonies of bacteria, would you culture your sample in a liquid
media or on a solid (agar) media? Why? (short answer) - ANS Solid media. The primary
advantage is that cells are held into place. When grown in a nutrient broth, bacterial cells can
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
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.
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
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, Gamma hemolysis (matching) - ANS No hemolytic activity
Columbia CNA agar is most closely related to which media (multiple choice) - ANS CNA agar is
similar to VAP as it is also enriched with blood and allows for differentiation based on hemolytic
patterns
True or False: Chocolate agar gets its brown color from cocoa to produce an enriched media -
ANS False
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
non-pathogenic e coli can ferment both sorbitol and lactose. Therefore, colonies that ferment
can be differentiated from non-fermenters.
What is the gram status of microbes growing on eosin methylene blue agar plates? (short
answer) - ANS Gram-negative
What is the process of spreading a bacterial culture onto a petri dish? (short answer) -
ANS Plating
Mannitol salt agar will turn what color in the presence of the pathogenic strain staphylococcus
aureus? (short answer) - ANS Yellow
In order to visual individual colonies of bacteria, would you culture your sample in a liquid
media or on a solid (agar) media? Why? (short answer) - ANS Solid media. The primary
advantage is that cells are held into place. When grown in a nutrient broth, bacterial cells can
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
