BIO SCI M118L (MICROBIO LAB) QUIZ 1 QUESTIONS
WITH COMPLETE SOLUTIONS
catalase test methods and results Correct Answers Methods:
expose bacteria to hydrogen peroxide
Results: breakdown of hydrogen peroxide produces oxygen gas
=> if it bubbles, there is catalase
catalase test purpose Correct Answers Purpose: to determine
whether organism expresses enzyme catalase
complex media Correct Answers contains one or more
ingredients of unknown composition
defined media Correct Answers all components have been
characterized and are known
differential media Correct Answers allows one to distinguish
between different types of bacteria growing on a single plate
- colored dyes taken up by specific organisms
- pH indicators that alter the color of media surrounding a
colony depending on the secretion
dye in oxidase paper Correct Answers N,N-dimethyl
phenylenediamine
E. coli Correct Answers - gram negative bacteria
- facultative
- lactose-fermenting
- enteric bacteria
, EMB media Correct Answers - Differential: contains eosin and
methylene blue (dyes) that are taken up by lactose fermenting
organisms
- Selective: prevent growth of gram positive organisms by
interfering with the formation of their cell walls
endospore test Correct Answers determines whether organism
can form spores
enriched media Correct Answers contains ingredients that
promote the growth of fastidious organisms
example of bacteria that cannot grow in minimal media Correct
Answers Streptococcus
example of differential media Correct Answers MacConkey
agar: contains pH indicator neutral red
- organisms that ferment lactose (sugar in the media) produce an
acid end product -> lowers pH -> turns red
- organisms that do not ferment lactose remain colorless
example of enriched media Correct Answers chocolate agar:
contains red blood cells lysed with heat -> permits growth of
organisms that require growth factors found inside red blood
cells
example of selective media Correct Answers MacConkey agar:
contains bile salts that destroy the cell walls of gram positive
bacteria, inhibiting their growth -> only gram negative bacteria
can grow
WITH COMPLETE SOLUTIONS
catalase test methods and results Correct Answers Methods:
expose bacteria to hydrogen peroxide
Results: breakdown of hydrogen peroxide produces oxygen gas
=> if it bubbles, there is catalase
catalase test purpose Correct Answers Purpose: to determine
whether organism expresses enzyme catalase
complex media Correct Answers contains one or more
ingredients of unknown composition
defined media Correct Answers all components have been
characterized and are known
differential media Correct Answers allows one to distinguish
between different types of bacteria growing on a single plate
- colored dyes taken up by specific organisms
- pH indicators that alter the color of media surrounding a
colony depending on the secretion
dye in oxidase paper Correct Answers N,N-dimethyl
phenylenediamine
E. coli Correct Answers - gram negative bacteria
- facultative
- lactose-fermenting
- enteric bacteria
, EMB media Correct Answers - Differential: contains eosin and
methylene blue (dyes) that are taken up by lactose fermenting
organisms
- Selective: prevent growth of gram positive organisms by
interfering with the formation of their cell walls
endospore test Correct Answers determines whether organism
can form spores
enriched media Correct Answers contains ingredients that
promote the growth of fastidious organisms
example of bacteria that cannot grow in minimal media Correct
Answers Streptococcus
example of differential media Correct Answers MacConkey
agar: contains pH indicator neutral red
- organisms that ferment lactose (sugar in the media) produce an
acid end product -> lowers pH -> turns red
- organisms that do not ferment lactose remain colorless
example of enriched media Correct Answers chocolate agar:
contains red blood cells lysed with heat -> permits growth of
organisms that require growth factors found inside red blood
cells
example of selective media Correct Answers MacConkey agar:
contains bile salts that destroy the cell walls of gram positive
bacteria, inhibiting their growth -> only gram negative bacteria
can grow
