Microbiology Lab - Exam 2 Questions
and Answers 100% Pass
medium - ✔✔a mixture of nutritional substances on or in which microorganisms grow
autotroph - ✔✔nutritionally deficient mutants that have lost the ability to synthesize a
particular enzyme
many microorganisms in this group:
- can carry out photosynthesis
- usually do not cause disease
- synthesize organic compounds to obtain energy
heterotroph - ✔✔an organism that uses compounds to produce biomolecules
autoclave - ✔✔an instrument for sterilization by means of moist heat under pressure
Autoclaving combines ____ and ____ to destroy high resistant bacteria. - ✔✔high temp
and high pressure
Katelyn Whitman, All Rights Reserved © 2025 1
,What are six basic nutritional requirements of every living thing? - ✔✔Water, carbon,
nitrogen, metallic elements, energy and growth factors such as vitamins
general purpose media - ✔✔Designed to grow a broad spectrum of microbes that do
not have special growth requirements
enriched media - ✔✔medium that contains special additives that could promote certain
metabolic activities. (ex. trypticase soy agar, blood agar, yeast extract broth)
- especially used for fastidious bacteria
selective media - ✔✔is a nutrient that inhibits the growth of a certain type of
microorganisms (ex. Gram + bacteria) while permitting the growth of a different type
(in this example, Gram - )
differential media - ✔✔medium which will differentiate between bacteria based on how
they change the medium or their appearance on the medium
EMB and HE are both ____ and ____. - ✔✔selective and differential
EMB and HE are selective for ____ and differential for ____. - ✔✔selective for gram-
negative bacteria and differential for lactose fermenters.
What do lactose fermenters and nonfermenters look like on each media? - ✔✔-
Organisms which quickly ferment lactose will give dark-green to black colonies on this
medium; these colonies have a metallic sheen (Ecoli)
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, - Organisms that are slow fermenters of lactose will give pink to maroon colonies on
this medium. Those organisms that cannot ferment lactose at all give white (colorless)
colonies on EMB agar (since nonfermenters of lactose are often high pathogenic, this is a
useful way to identify potential pathogens)
What is Shigella associated with? - ✔✔a genus associated with bacillary dysentery
HE and EMB are useful for distinguishing between _____. - ✔✔Enterobacteriaceae
What are Enterobacteriaceae? - ✔✔a group of short, Gram-negative, facultative
anaerobic rods that are found in the intestinal tract of various mammals, including
humans
PEA and MS agar are _____ for ____. - ✔✔selective for gram-positive bacteria
MS is _____ and _____ for _____. - ✔✔selective and differential for mannitol fermenters
What bacterial genus is Mannitol Salt (MS) agar used to distinguish? -
✔✔Staphylococcus -- high levels of salt in medium are tolerated by its cells
What do fermenters and non-fermenters look like on Mannitol Salt (MS) agar? - ✔✔-
fermentation of mannitol causes the medium to turn deep yellow in the area of bacterial
growth
- if mannitol not fermented, the color of the medium will remain pink
Katelyn Whitman, All Rights Reserved © 2025 3
and Answers 100% Pass
medium - ✔✔a mixture of nutritional substances on or in which microorganisms grow
autotroph - ✔✔nutritionally deficient mutants that have lost the ability to synthesize a
particular enzyme
many microorganisms in this group:
- can carry out photosynthesis
- usually do not cause disease
- synthesize organic compounds to obtain energy
heterotroph - ✔✔an organism that uses compounds to produce biomolecules
autoclave - ✔✔an instrument for sterilization by means of moist heat under pressure
Autoclaving combines ____ and ____ to destroy high resistant bacteria. - ✔✔high temp
and high pressure
Katelyn Whitman, All Rights Reserved © 2025 1
,What are six basic nutritional requirements of every living thing? - ✔✔Water, carbon,
nitrogen, metallic elements, energy and growth factors such as vitamins
general purpose media - ✔✔Designed to grow a broad spectrum of microbes that do
not have special growth requirements
enriched media - ✔✔medium that contains special additives that could promote certain
metabolic activities. (ex. trypticase soy agar, blood agar, yeast extract broth)
- especially used for fastidious bacteria
selective media - ✔✔is a nutrient that inhibits the growth of a certain type of
microorganisms (ex. Gram + bacteria) while permitting the growth of a different type
(in this example, Gram - )
differential media - ✔✔medium which will differentiate between bacteria based on how
they change the medium or their appearance on the medium
EMB and HE are both ____ and ____. - ✔✔selective and differential
EMB and HE are selective for ____ and differential for ____. - ✔✔selective for gram-
negative bacteria and differential for lactose fermenters.
What do lactose fermenters and nonfermenters look like on each media? - ✔✔-
Organisms which quickly ferment lactose will give dark-green to black colonies on this
medium; these colonies have a metallic sheen (Ecoli)
Katelyn Whitman, All Rights Reserved © 2025 2
, - Organisms that are slow fermenters of lactose will give pink to maroon colonies on
this medium. Those organisms that cannot ferment lactose at all give white (colorless)
colonies on EMB agar (since nonfermenters of lactose are often high pathogenic, this is a
useful way to identify potential pathogens)
What is Shigella associated with? - ✔✔a genus associated with bacillary dysentery
HE and EMB are useful for distinguishing between _____. - ✔✔Enterobacteriaceae
What are Enterobacteriaceae? - ✔✔a group of short, Gram-negative, facultative
anaerobic rods that are found in the intestinal tract of various mammals, including
humans
PEA and MS agar are _____ for ____. - ✔✔selective for gram-positive bacteria
MS is _____ and _____ for _____. - ✔✔selective and differential for mannitol fermenters
What bacterial genus is Mannitol Salt (MS) agar used to distinguish? -
✔✔Staphylococcus -- high levels of salt in medium are tolerated by its cells
What do fermenters and non-fermenters look like on Mannitol Salt (MS) agar? - ✔✔-
fermentation of mannitol causes the medium to turn deep yellow in the area of bacterial
growth
- if mannitol not fermented, the color of the medium will remain pink
Katelyn Whitman, All Rights Reserved © 2025 3
