MBIO 3400 Lab Exam 2 Questions &
Answers (Grade A+)
Specialized media is used for -
correct answer ✅To isolate desired microbes from mixed cultures
Differential media varies from selective media in that -
correct answer ✅Growth of organisms is not inhibited, but allow
certain groups of bacteria to appear differently than others when
grown on the same media and even permit identification based on
their biological characteristics
Selective and differential media are used when -
correct answer ✅Isolating bacteria from a source where it is
suspected that there is more than one organism present
Selective agents -
correct answer ✅Prohibit the growth of some organisms
Selective medium -
correct answer ✅Allows the organism of interest to grow while
inhibiting growth of others
Name 2 examples of selective media -
correct answer ✅MacConkeys agar and Mannitol Salt Agar
,MBIO 3400 Lab Exam 2 Questions &
Answers (Grade A+)
MacConkeys agar contains __ and ___ that -
correct answer ✅Crystal violet and bile salts that allow the growth
of GRAM NEGATIVE organisms
Mannitol salt agar allows the growth of __ because -
correct answer ✅GRAM POSITIVE because it contains high levels
of salt (7.5%); inhibits growth of gram negative due to osmotic
stress
The principle behind differentiating media is that -
correct answer ✅Different bacteria produce different end products
when grown on the same nutrients
What is one of the most common differential agents -
correct answer ✅pH indicator-can distinguish between acidic or
basic end products of metabolism
What type of media contains lactose and neutral red -
correct answer ✅macConkeys
,MBIO 3400 Lab Exam 2 Questions &
Answers (Grade A+)
What type of media contains mannitol and phenol red -
correct answer ✅Mannitol salt agar
Describe the color change of MacConkeys agar -
correct answer ✅If the organism is capable of utilizing lactose, it
produces acidic end products, lowering the pH and turns colonies
RED RED (non-lactose stays transparent but background stays red)
Describe color change of mannitol salt agar -
correct answer ✅When mannitol is fermented, pH drops and
medium/colony turns YELLOW. (non fermenters stays pink)
What is KIA -
correct answer ✅Kilgers iron agar: differential medium which is
used to differentiate between ENTERIC BACTERIA based on their
ability to reduce sulfur and carbohydrates
what is KIA medium composed of -
correct answer ✅glucose, lactose, sucrose, ferrous, sulfate,
peptone, and the phenol red pH indicator
, MBIO 3400 Lab Exam 2 Questions &
Answers (Grade A+)
What are enterics -
correct answer ✅Gram negative facultative bacilli which ferment
the carbohydrate glucose to acidic end products. Many are
pathogenic
How is KIA medium prepared and inoculated? -
correct answer ✅Prepared as an agar slant. Inoculated with a
NEEDLE. First agar is stabbed and then streaked
Describe the color changes in KIA tests -
correct answer ✅Glucose utilization with acid production is
indicated by yellow color throughout the medium
In the KIA test, If the organism utilizes lactose, it will also utilize -
correct answer ✅Glucose
How could you geta false lactose negative result (KIA test)? -
correct answer ✅The slant turns yellow because of lactose use.
After exhaustion of the lactose, the slant will turn red due to
peptone metabolism
Answers (Grade A+)
Specialized media is used for -
correct answer ✅To isolate desired microbes from mixed cultures
Differential media varies from selective media in that -
correct answer ✅Growth of organisms is not inhibited, but allow
certain groups of bacteria to appear differently than others when
grown on the same media and even permit identification based on
their biological characteristics
Selective and differential media are used when -
correct answer ✅Isolating bacteria from a source where it is
suspected that there is more than one organism present
Selective agents -
correct answer ✅Prohibit the growth of some organisms
Selective medium -
correct answer ✅Allows the organism of interest to grow while
inhibiting growth of others
Name 2 examples of selective media -
correct answer ✅MacConkeys agar and Mannitol Salt Agar
,MBIO 3400 Lab Exam 2 Questions &
Answers (Grade A+)
MacConkeys agar contains __ and ___ that -
correct answer ✅Crystal violet and bile salts that allow the growth
of GRAM NEGATIVE organisms
Mannitol salt agar allows the growth of __ because -
correct answer ✅GRAM POSITIVE because it contains high levels
of salt (7.5%); inhibits growth of gram negative due to osmotic
stress
The principle behind differentiating media is that -
correct answer ✅Different bacteria produce different end products
when grown on the same nutrients
What is one of the most common differential agents -
correct answer ✅pH indicator-can distinguish between acidic or
basic end products of metabolism
What type of media contains lactose and neutral red -
correct answer ✅macConkeys
,MBIO 3400 Lab Exam 2 Questions &
Answers (Grade A+)
What type of media contains mannitol and phenol red -
correct answer ✅Mannitol salt agar
Describe the color change of MacConkeys agar -
correct answer ✅If the organism is capable of utilizing lactose, it
produces acidic end products, lowering the pH and turns colonies
RED RED (non-lactose stays transparent but background stays red)
Describe color change of mannitol salt agar -
correct answer ✅When mannitol is fermented, pH drops and
medium/colony turns YELLOW. (non fermenters stays pink)
What is KIA -
correct answer ✅Kilgers iron agar: differential medium which is
used to differentiate between ENTERIC BACTERIA based on their
ability to reduce sulfur and carbohydrates
what is KIA medium composed of -
correct answer ✅glucose, lactose, sucrose, ferrous, sulfate,
peptone, and the phenol red pH indicator
, MBIO 3400 Lab Exam 2 Questions &
Answers (Grade A+)
What are enterics -
correct answer ✅Gram negative facultative bacilli which ferment
the carbohydrate glucose to acidic end products. Many are
pathogenic
How is KIA medium prepared and inoculated? -
correct answer ✅Prepared as an agar slant. Inoculated with a
NEEDLE. First agar is stabbed and then streaked
Describe the color changes in KIA tests -
correct answer ✅Glucose utilization with acid production is
indicated by yellow color throughout the medium
In the KIA test, If the organism utilizes lactose, it will also utilize -
correct answer ✅Glucose
How could you geta false lactose negative result (KIA test)? -
correct answer ✅The slant turns yellow because of lactose use.
After exhaustion of the lactose, the slant will turn red due to
peptone metabolism
