Microbiology Lab - Exam 2 with
Complete Solutions
medium Correct Ans-a mixture of nutritional substances on or in which microorganisms grow
autotroph Correct Ans-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 Correct Ans-an organism that uses compounds to produce biomolecules
autoclave Correct Ans-an instrument for sterilization by means of moist heat under pressure
Autoclaving combines ____ and ____ to destroy high resistant bacteria. Correct Ans-high
temp and high pressure
What are six basic nutritional requirements of every living thing? Correct Ans-Water, carbon,
nitrogen, metallic elements, energy and growth factors such as vitamins
,general purpose media Correct Ans-Designed to grow a broad spectrum of microbes that do
not have special growth requirements
enriched media Correct Ans-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 Correct Ans-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 Correct Ans-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 ____. Correct Ans-selective and differential
EMB and HE are selective for ____ and differential for ____. Correct Ans-selective for gram-
negative bacteria and differential for lactose fermenters.
What do lactose fermenters and nonfermenters look like on each media? Correct Ans--
Organisms which quickly ferment lactose will give dark-green to black colonies on this medium;
these colonies have a metallic sheen (Ecoli)
, - 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? Correct Ans-a genus associated with bacillary dysentery
HE and EMB are useful for distinguishing between _____. Correct Ans-Enterobacteriaceae
What are Enterobacteriaceae? Correct Ans-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 ____. Correct Ans-selective for gram-positive bacteria
MS is _____ and _____ for _____. Correct Ans-selective and differential for mannitol
fermenters
What bacterial genus is Mannitol Salt (MS) agar used to distinguish? Correct Ans-
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? Correct Ans--
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
Complete Solutions
medium Correct Ans-a mixture of nutritional substances on or in which microorganisms grow
autotroph Correct Ans-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 Correct Ans-an organism that uses compounds to produce biomolecules
autoclave Correct Ans-an instrument for sterilization by means of moist heat under pressure
Autoclaving combines ____ and ____ to destroy high resistant bacteria. Correct Ans-high
temp and high pressure
What are six basic nutritional requirements of every living thing? Correct Ans-Water, carbon,
nitrogen, metallic elements, energy and growth factors such as vitamins
,general purpose media Correct Ans-Designed to grow a broad spectrum of microbes that do
not have special growth requirements
enriched media Correct Ans-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 Correct Ans-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 Correct Ans-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 ____. Correct Ans-selective and differential
EMB and HE are selective for ____ and differential for ____. Correct Ans-selective for gram-
negative bacteria and differential for lactose fermenters.
What do lactose fermenters and nonfermenters look like on each media? Correct Ans--
Organisms which quickly ferment lactose will give dark-green to black colonies on this medium;
these colonies have a metallic sheen (Ecoli)
, - 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? Correct Ans-a genus associated with bacillary dysentery
HE and EMB are useful for distinguishing between _____. Correct Ans-Enterobacteriaceae
What are Enterobacteriaceae? Correct Ans-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 ____. Correct Ans-selective for gram-positive bacteria
MS is _____ and _____ for _____. Correct Ans-selective and differential for mannitol
fermenters
What bacterial genus is Mannitol Salt (MS) agar used to distinguish? Correct Ans-
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? Correct Ans--
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
