Topic 6 - Cultivation - Clickers Flashcards
What is this medium?
a) Complex
b) Defined
a) Complex
Explanation: A medium is considered complex if it contains ingredients with unknown or variable chemical compositions, such as yeast extract, proteose peptone, and casamino acids, which are present in R2A. These components are hydrolysates of biological materials and include a variety of nutrients whose exact composition cannot be precisely defined.
In contrast, a defined medium would only contain components with known and exact chemical formulas in specified amounts.
Which best describes this growth medium? (picture of spaghetti dinner)
a) defined
b) complex
b) complex
Explanation: Complex media contain ingredients like yeast extract or peptone, where the exact composition is not fully known. Spaghetti dinner represents a mixture with undefined components.
What best describes this growth medium? (picture of asparagus, shrimp, and potato)
a) defined
b) complex
b) complex
Explanation: Complex media include natural ingredients, such as asparagus and shrimp, where the exact chemical composition is variable or unknown.
Which best describes this growth medium? (picture of plate with specific chemicals and their masses, like glucose, potassium acetate, etc.)
a) defined
b) complex
a) defined
Explanation: Defined media have a known and exact chemical composition, as shown by the specific chemicals listed in the medium.
Which best describes this growth medium? (picture of an agar plate with colonies on it)
a) defined
b) complex
c) don’t know
c) don’t know
Explanation: The composition of the growth medium is unknown based on the given context, so ‘don’t know’ is the best choice.
A new form of microbial life has been discovered. It uses light for energy and grows on acetate and other organic acids. This organism is classified as being a:
a) Chemoorganoautotroph
b) Chemolithoheterotroph
c) Photoorganoheterotroph
d) Photoorganoautotroph
c) Photoorganoheterotroph
Explanation: This organism uses light for energy (photo) and organic acids as a carbon source (heterotroph).
A new form of microbial life has been discovered. It uses light for energy and iron for electrons. This organism is best classified as a:
a) Photolithoautotroph
b) Photoorganoheterotroph
c) Photolithotroph
d) Photoorganotroph
c) Photolithotroph
Explanation: The organism uses light for energy (photo) and an inorganic electron donor (litho).
Dr. Neufeld is trying to isolate a new organism. His medium inhibits the growth of fungus using cycloheximide, and contains a pH indicator to help identify his bacterium. His medium is:
a) Differential and enriched
b) Selective and enriched
c) Differential
d) Selective and differential
e) Selective
d) Selective and differential
Explanation: The medium is selective because cycloheximide inhibits the growth of fungi, and it is differential because the pH indicator allows for differentiation based on metabolic activity.
You are growing a culture of Vibrio natriegens in the lab and would like to measure the number of viable cells over time. Which method(s) could be used?
a) Direct count
b) Spread plate or pour plate or direct count
c) Spread plate
d) Pour plate
e) Spread plate or pour plate
e) Spread plate or pour plate
Explanation: Spread plate and pour plate methods are used to measure viable cell counts because they only count living cells capable of forming colonies.
You are growing a culture of Vibrio natriegens in the lab and would like to prepare a growth curve before tomorrow’s lab report is due (you must be quick!). Which method would you use?
a) Spectrophotometer
b) Spread plate
c) Direct count
d) Pour plate
a) Spectrophotometer
Explanation: The spectrophotometer is a quick method to estimate cell density by measuring optical density, which is ideal for time-sensitive growth curve generation.
You are growing a culture of Vibrio natriegens in the lab and would like to prepare a growth curve before tomorrow’s lab report is due (you must be quick!). Which method would you use if you could only select from the list below?
a) Pour plate
b) Spread plate
c) Direct count
c) Direct count
Explanation: Direct counting, often using a hemocytometer or similar device, provides rapid estimates of cell number, even though it includes both live and dead cells.
A serial dilution of a culture is performed. The dilution factor is 10-3. After 1 ml of diluted solution was included in a pour plate and incubated, 40 colonies grew. How many colony forming units (CFU) per ml were present in the original culture?
a) 40
b) 400
c) 4000
d) 40000
d) 40000
Explanation: The original culture’s CFU/ml is calculated as the number of colonies (40) multiplied by the dilution factor’s inverse (103), resulting in 40,000 CFU/ml.
What is the approximate generation time of Bacillus subtilis?
a) 0.5 h
b) 1 h
c) 2 h
d) 3 h
e) 4 h
b) 1 h
Duplicate 100 µl aliquots were spread on plates from a 1 in 10 culture dilution. The next day, 30 and 50 colonies grew on the two plates. How many colony forming units (CFU) per ml were present in the original culture (reported as an average)?
a) 40
b) 400
c) 4000
d) 40000
e) 400000
c) 4000
Explanation: The average number of colonies is (30 + 50)/2 = 40. Since 100 µl aliquots were used, the CFU per ml = 40 x 10 (dilution factor) x 10 (to account for 100 µl) = 4000.
The generation time of a culture is constant in the lab. This is because the culture is in ________.
a) lag phase
b) exponential phase
c) stationary phase
d) death phase
b) exponential phase
Explanation: During the exponential phase, cells divide at a constant rate, leading to a constant generation time in the lab.
Mechanism?
a) bacteriocidal
b) bacteriolytic
c) bacteriostatic
b) bacteriolytic
Notice the red “ring”… what group of antibiotics does this look like to you?
Explanation: The red “ring” structure shown in the image is characteristic of a β-lactam antibiotic, such as penicillin. β-lactam antibiotics inhibit bacterial cell wall synthesis by targeting penicillin-binding proteins (PBPs), which are crucial for peptidoglycan cross-linking. This disruption weakens the bacterial cell wall, causing the cell to lyse due to osmotic pressure, leading to a bacteriolytic effect. The key mechanism involves the destruction of bacterial integrity, not just growth inhibition.
What is the approximate growth rate of E. coli if its generation time in a particular medium is 30 min (0.5 h)?
a) 0.5 h⁻1
b) 1 h⁻1
c) 2 h⁻1
d) 3 h⁻1
e) 4 h⁻1
c) 2 h⁻1
Explanation: The growth rate is the reciprocal of the generation time. For a generation time of 0.5 h, the growth rate is 1/0.5 = 2 h⁻1
What would the CFU ml⁻¹ of the original culture be for a spread plate with 234 colonies arising from a 0.1 ml aliquot and a dilution factor of 10⁻⁶?
a) 2.34 × 10⁷
b) 2.34 × 10⁸
c) 2.34 × 10⁹
d) 2.34 × 10¹⁰
e) 2.34 × 10⁶
c) 2.34 × 10⁹
Explanation: CFU/ml = (colonies × dilution factor) / volume plated = (234 × 10⁶) / 0.1 = 2.34 × 10⁹ CFU/ml.
Autoclave time for 500 mL of medium is 25 minutes; the sterilization time is 15 minutes. For 1 L of medium, autoclave time is 50 minutes. How long should the sterilization time be?
a) 20 min
b) 25 min
c) 30 min
d) >15 min
e) 15 min
e) 15 min
Explanation: The sterilization time is independent of the medium volume; it is constant at 15 minutes.
Dr. Neufeld hands you a psychrotolerant bacterial isolate, asks you to grow it, then walks away. What range would you predict for its optimum growth temperature (in degrees Celsius)?
a) <5
b) 5-10
c) 10-20
d) 20-40
e) >40
d) 20-40
Explanation: Psychrotolerant bacteria can grow at low temperatures but typically have an optimum growth range of 20-40°C.
The decimal reduction time (D) for a species of bacteria is 10 minutes at 60°C. What do you expect the decimal reduction time to be at 70°C?
a) 20 minutes
b) 5 minutes
c) >10 minutes
d) <10 minutes
e) No way to tell
d) <10 minutes
Explanation: Higher temperatures reduce the decimal reduction time due to increased bacterial death rates.
The decimal reduction dose (D10) for a species of bacteria at 300 Grays. If we start out with 1,000,000 viable bacteria in a culture, how many do we expect to remain viable after a 900 Gray exposure?
100
1,000
10,000
100,000
b) 1,000
Explanation: The D10 value indicates the dose required to reduce the viable count by 90%. For 900 Grays, which is 3 times the D10, the viable count will decrease by 10sup>3</sup> (1,000-fold), leaving 1,000 viable cells.
Oh good, a doctor! We have a patient that needs a maximally broad spectrum antibiotic treatment as quickly as possible, even better if bacteriostatic to avoid septic shock. Please hurry!
Chloramphenicol
Tetracycline
Polymyxin B
Penicillin
Ampicillin
b) Tetracycline
Explanation: Tetracycline is a bacteriostatic antibiotic with a broad spectrum of activity, making it suitable for treating a wide range of bacterial infections.
Please filter-sterilize this growth medium for me.
membrane
nucleopore
depth
a) membrane
Explanation: Membrane filters are typically used for sterilization as they effectively remove microorganisms while allowing the passage of liquids.
All of these would INCREASE the generation time of a bacteria, except for one. Find it!
a) Temperature lowered below optimum
b) Inoculation into a different growth medium
c) Supplying oxygen to a facultative anaerobe
d) Competition from other bacteria
e) Macronutrient becomes limiting
c) Supplying oxygen to a facultative anaerobe
Explanation: Supplying oxygen to a facultative anaerobe would decrease its generation time because it allows the organism to switch to aerobic respiration, which is more efficient than anaerobic processes.
Penicillin acts on what?
a) FtsZ and transglycosylation
b) FtsI and transglycosylation
c) FtsZ and transpeptidation
d) FtsI and transpeptidation
d) FtsI and transpeptidation
Explanation: Penicillin targets the FtsI protein involved in transpeptidation, inhibiting bacterial cell wall synthesis by preventing cross-linking of peptidoglycan strands.
In the early 70s, David Schindler tested the impact of _______ macronutrient additions on boreal shield lake primary productivity.
a) Phosphorous
b) Sodium
c) Manganese
d) Copper
e) Magnesium
a) Phosphorous
Explanation: Phosphorous was the critical macronutrient identified by Schindler as limiting primary productivity in boreal shield lakes, leading to algal blooms when added.
Working out often leaves muscles sore from lactic acid production. No surprise: _________.
a) microaerophilic
b) aerotolerant
c) obligate anaerobes
d) facultative anaerobes
e) aerobic
d) facultative anaerobes
Explanation: Facultative anaerobes can produce lactic acid during anaerobic metabolism, which occurs when oxygen levels are low, such as during intense physical activity.
