Microbiology lab exam 2 with Verified
Solutions
gram-positive Correct Ans-appear purple
gram-negative Correct Ans-appear pink
Isolation by Dilution Correct Ans--reducing number of bacteria so that individual colonies
may be isolated
-streak plate technique is commonly used to separate mixed cultures to isolate colonies that can
be used to make a pure culture
Selective media Correct Ans-promotes the growth of some organisms and inhibits the growth
of others
Differential media Correct Ans-show different growth characteristics for certain organisms,
such as a color change
TSA Correct Ans-Tryptic Soy Agar
-neither selective nor differential
MSA Correct Ans-Mannitol Salt Agar
-both selective and differential
, -selects for salt tolerant (halophiles)
-differential- mannitol fermenters change media from red to yellow
EMB Correct Ans-Eosin Methylene Blue Agar
-both selective and differential
-selects for gram-negative and inhibits gram-positive
-differential- lactose fermenters exhibit metallic green sheen
Carbohydrate Catabolism labs Correct Ans-Starch hydrolysis and OF glucose deeps
Starch hydrolysis Correct Ans--differential test
-if starch is no longer in media, the bacteria will test positive for amylase
-Flood agar with iodine; iodine will turn media purple if it contains starch
-positive result will have zone of clearing and no color change in media
-negative result will have no zone of clearing and color change of media to dark purple
OF glucose deep Correct Ans-Oxidative/Fermentative
-blue/green
-one tube is covered with mineral oil to create anaerobic conditions
-positive result is color change in media from green to yellow indicating acid production;
negative result is no color change
-both tubes yellow=fermentative
Solutions
gram-positive Correct Ans-appear purple
gram-negative Correct Ans-appear pink
Isolation by Dilution Correct Ans--reducing number of bacteria so that individual colonies
may be isolated
-streak plate technique is commonly used to separate mixed cultures to isolate colonies that can
be used to make a pure culture
Selective media Correct Ans-promotes the growth of some organisms and inhibits the growth
of others
Differential media Correct Ans-show different growth characteristics for certain organisms,
such as a color change
TSA Correct Ans-Tryptic Soy Agar
-neither selective nor differential
MSA Correct Ans-Mannitol Salt Agar
-both selective and differential
, -selects for salt tolerant (halophiles)
-differential- mannitol fermenters change media from red to yellow
EMB Correct Ans-Eosin Methylene Blue Agar
-both selective and differential
-selects for gram-negative and inhibits gram-positive
-differential- lactose fermenters exhibit metallic green sheen
Carbohydrate Catabolism labs Correct Ans-Starch hydrolysis and OF glucose deeps
Starch hydrolysis Correct Ans--differential test
-if starch is no longer in media, the bacteria will test positive for amylase
-Flood agar with iodine; iodine will turn media purple if it contains starch
-positive result will have zone of clearing and no color change in media
-negative result will have no zone of clearing and color change of media to dark purple
OF glucose deep Correct Ans-Oxidative/Fermentative
-blue/green
-one tube is covered with mineral oil to create anaerobic conditions
-positive result is color change in media from green to yellow indicating acid production;
negative result is no color change
-both tubes yellow=fermentative
