TTU Mbio Lab Exam 2 Questions with
complete solution
What genera (genus) does Stuart's Urea Broth test for? - correct answer ✔-
Proteus genus
What pH indicator is used in Stuart's Urea Broth? - correct answer ✔- phenol
red
What pH does it change for Urea positive colors and what color? - correct
answer ✔- phenol red turns from orange to pink at 8.4 pH
- positive = if it contains urea phenol red, it turns pink 8.4
Negative = stays orange
How does the Stuart's Urea broth work? - correct answer ✔to overcome the
buffer and raise the pH, the bacteria must produce ammonia
What enzyme is used to break down urea and into what molecule? - correct
answer ✔- urease = an enzyme that catalyzes the hydrolysis of ammonia and
carbon dioxide
Know that bacteria can utilize sugars differently, what test can be done to
check carbohydrate utilization of several sugars? - correct answer ✔-
carbohydrate fermentation
- common end products = pyruvic acid, H2 or CO2 gases, and alcohols
- if it utilizes gas, the Durham tube's liquid decreases
- we used glucose, lactose, sucrose and maltose broth for each bacteria
, What is the carbohydrate fermentation test made of? - correct answer
✔phenol red, peptone, carbohydrate
In carbohydrate fermentation, what pH indicator is used and what pH and
color does it change to positive result? - correct answer ✔- phenol red
-negative= pink = above 7.4 pH
- positive = yellow= less than 6.8 pH
What is the purpose of the inverted Durham tube? - correct answer ✔- to see
if gas was produced during metabolism
What is an antibiotic? - correct answer ✔- a type of chemical synthesized by
living organisms that has antimicrobial properties
- it can either kill the organism (bactericidial effect) or stop it from growing
(bacteriostatic effect)
How is an Antibiotic sensitivity test done? - correct answer ✔- by growing
pure colonies of the diagnosed infectious agent on agar plates and placing
antibiotic-soaked paper discs on top of the agar
- as the plates incubate - the antibiotics diffuse from the discs into the culture
medium
- the antibiotic becomes more diluted from the incubationand moves away
from the disc
What is the difference between bacteriostatic and bactericidal? - correct
answer ✔- kill the organism (bactericidial effect)
- stop it from growing (bacteriostatic effect)
What factors impact the zone of inhibition? - correct answer ✔- if the
antibiotic is effective or not
complete solution
What genera (genus) does Stuart's Urea Broth test for? - correct answer ✔-
Proteus genus
What pH indicator is used in Stuart's Urea Broth? - correct answer ✔- phenol
red
What pH does it change for Urea positive colors and what color? - correct
answer ✔- phenol red turns from orange to pink at 8.4 pH
- positive = if it contains urea phenol red, it turns pink 8.4
Negative = stays orange
How does the Stuart's Urea broth work? - correct answer ✔to overcome the
buffer and raise the pH, the bacteria must produce ammonia
What enzyme is used to break down urea and into what molecule? - correct
answer ✔- urease = an enzyme that catalyzes the hydrolysis of ammonia and
carbon dioxide
Know that bacteria can utilize sugars differently, what test can be done to
check carbohydrate utilization of several sugars? - correct answer ✔-
carbohydrate fermentation
- common end products = pyruvic acid, H2 or CO2 gases, and alcohols
- if it utilizes gas, the Durham tube's liquid decreases
- we used glucose, lactose, sucrose and maltose broth for each bacteria
, What is the carbohydrate fermentation test made of? - correct answer
✔phenol red, peptone, carbohydrate
In carbohydrate fermentation, what pH indicator is used and what pH and
color does it change to positive result? - correct answer ✔- phenol red
-negative= pink = above 7.4 pH
- positive = yellow= less than 6.8 pH
What is the purpose of the inverted Durham tube? - correct answer ✔- to see
if gas was produced during metabolism
What is an antibiotic? - correct answer ✔- a type of chemical synthesized by
living organisms that has antimicrobial properties
- it can either kill the organism (bactericidial effect) or stop it from growing
(bacteriostatic effect)
How is an Antibiotic sensitivity test done? - correct answer ✔- by growing
pure colonies of the diagnosed infectious agent on agar plates and placing
antibiotic-soaked paper discs on top of the agar
- as the plates incubate - the antibiotics diffuse from the discs into the culture
medium
- the antibiotic becomes more diluted from the incubationand moves away
from the disc
What is the difference between bacteriostatic and bactericidal? - correct
answer ✔- kill the organism (bactericidial effect)
- stop it from growing (bacteriostatic effect)
What factors impact the zone of inhibition? - correct answer ✔- if the
antibiotic is effective or not
