BIOS 260 Exam 2 with Verified Solutions 100% Solved
1. Explain how physical conditions such as temperature, pH, and oxygen can influence
bacterial growth. Correct Ans-Temp: can have an influence on the speed of growth
(including optimum growth), and too hot of temp can kill some bacteria.
pH: bacteria that are not adapted to live in acidic conditions will die when their proteins
denature.
O2: some bacteria require O2, some require the absence of O2, and others can survive in
either anaerobic or aerobic conditions.
H20: some bacteria require a specific water condition (less or more osmotic) to survive.
2. What is the optimum temperature for growth of psychrophiles, psychrotrophs, mesophiles,
and thermophiles? Correct Ans-psychophiles: -5-15 C
psychotrophs: 15-30 C
mesophile: 25-45 C
thermophile: 45-70 C
Hyperthermophile: 70+ C
3. What are the basic chemical requirements for bacterial growth? Correct Ans-Carbon
oxygen
, BIOS 260 Exam 2 with Verified Solutions 100% Solved
hydrogen
nitrogen
sulfur
phosphorus
potassium, magnesium, calcium
iron
4. What is the difference between chemically defined media and complex media? Correct
Ans-chemically defined media has measured and exact proportions of known solutes
(glucose, salts, water, etc)
complex media has various proportions of substances meant to be rich so growth is
encouraged.
5. What are selective media? What are differential media? Know some examples of each.
Correct Ans-selective media inhibits growth of certain species within a mixed sample. EX:
Thayer-Martin agar
1. Explain how physical conditions such as temperature, pH, and oxygen can influence
bacterial growth. Correct Ans-Temp: can have an influence on the speed of growth
(including optimum growth), and too hot of temp can kill some bacteria.
pH: bacteria that are not adapted to live in acidic conditions will die when their proteins
denature.
O2: some bacteria require O2, some require the absence of O2, and others can survive in
either anaerobic or aerobic conditions.
H20: some bacteria require a specific water condition (less or more osmotic) to survive.
2. What is the optimum temperature for growth of psychrophiles, psychrotrophs, mesophiles,
and thermophiles? Correct Ans-psychophiles: -5-15 C
psychotrophs: 15-30 C
mesophile: 25-45 C
thermophile: 45-70 C
Hyperthermophile: 70+ C
3. What are the basic chemical requirements for bacterial growth? Correct Ans-Carbon
oxygen
, BIOS 260 Exam 2 with Verified Solutions 100% Solved
hydrogen
nitrogen
sulfur
phosphorus
potassium, magnesium, calcium
iron
4. What is the difference between chemically defined media and complex media? Correct
Ans-chemically defined media has measured and exact proportions of known solutes
(glucose, salts, water, etc)
complex media has various proportions of substances meant to be rich so growth is
encouraged.
5. What are selective media? What are differential media? Know some examples of each.
Correct Ans-selective media inhibits growth of certain species within a mixed sample. EX:
Thayer-Martin agar
