BIOL 3201 Lab 5 and 6 Study Guide.
Selective Media - Answer medium that allows only certain microorganisms to grow and inhibit
the growth of other microorganisms
Differential Media - Answer medium that contains substances that cause some bacteria to
take on an appearance that distinguishes them from other bacteria
EMB - Answer Eosin Methylene Blue
selective and differential
How is EMB selective? - Answer dyes eosin and methylene blue no not affect the growth of
gram negative bacteria but inhibit the growth of gram positive bacteria
How is EMB differential? - Answer Gram negative bacteria that vigorously ferment lactose in
this medium form colonies with a metallic-green sheen. Gram negative bacteria that moderately
ferment lactose form purple colonies. Non-lactose-fermenting bacteria form pink or colorless
colonies (can see these colonies).
If an organism can breakdown carbohydrates by oxidation or fermentation what is usually
produced? - Answer acid
In phenol red carbohydrate test the presence of acid is indicated by - Answer a color change in
the pH indicator, phenol red, from red at alkaline pH values to yellow at acidic pH values
O/F carbohydrate tubes are used to: - Answer determine whether an organism actually
produces acid through fermentation or only through oxidation
how are phenol red tubes and O/F carbohydrate tubes different? - Answer O/F carbohydrate
tubes contain a semisolid agar rather than liquid. Helps to create an anaerobic environment in
the F tube that is needed for fermentation reactions
Both O and F tubes are turned yellows the organism: - Answer carry out fermentation of
carbohydrates
Organisms that turn only the O tube yellow: - Answer carry out fermentation and produce acid
only through the oxidative pathway (respiration)
Selective Media - Answer medium that allows only certain microorganisms to grow and inhibit
the growth of other microorganisms
Differential Media - Answer medium that contains substances that cause some bacteria to
take on an appearance that distinguishes them from other bacteria
EMB - Answer Eosin Methylene Blue
selective and differential
How is EMB selective? - Answer dyes eosin and methylene blue no not affect the growth of
gram negative bacteria but inhibit the growth of gram positive bacteria
How is EMB differential? - Answer Gram negative bacteria that vigorously ferment lactose in
this medium form colonies with a metallic-green sheen. Gram negative bacteria that moderately
ferment lactose form purple colonies. Non-lactose-fermenting bacteria form pink or colorless
colonies (can see these colonies).
If an organism can breakdown carbohydrates by oxidation or fermentation what is usually
produced? - Answer acid
In phenol red carbohydrate test the presence of acid is indicated by - Answer a color change in
the pH indicator, phenol red, from red at alkaline pH values to yellow at acidic pH values
O/F carbohydrate tubes are used to: - Answer determine whether an organism actually
produces acid through fermentation or only through oxidation
how are phenol red tubes and O/F carbohydrate tubes different? - Answer O/F carbohydrate
tubes contain a semisolid agar rather than liquid. Helps to create an anaerobic environment in
the F tube that is needed for fermentation reactions
Both O and F tubes are turned yellows the organism: - Answer carry out fermentation of
carbohydrates
Organisms that turn only the O tube yellow: - Answer carry out fermentation and produce acid
only through the oxidative pathway (respiration)
