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TestMaster MCQs

Bacterial Growth & Metabolism Questions

Home Science Bacterial Growth & Metabolism
Q. Binary fission is the process by which bacteria:
Reproduce asexually
Become dormant
Transfer DNA
Form spores

Explanation:

Binary fission is asexual reproduction producing two identical daughter cells.

Q. The bacterial growth curve has how many phases?
Five
Four
Two
Three

Explanation:

The bacterial growth curve has four phases: lag, log (exponential), stationary, and death.

Q. During which phase do bacteria grow fastest?
Death phase
Stationary phase
Lag phase
Log (exponential) phase

Explanation:

Log (exponential) phase is when bacteria grow and divide at maximum rate.

Q. In the lag phase, bacteria:
Divide rapidly
Adapt without dividing
Die
Form spores

Explanation:

During lag phase, bacteria adapt to new conditions but do not divide.

Q. In the stationary phase:
Bacteria divide fastest
Bacteria form spores only
All bacteria die
Growth rate equals death rate

Explanation:

Stationary phase occurs when growth rate equals death rate, so total cell number stays constant.

Q. Generation time is:
Time to become dormant
Time to form spores
Time for population to double
Time to transfer DNA

Explanation:

Generation time is the time required for a bacterial population to double.

Q. Bacteria that grow best at human body temperature are:
Psychrophiles
Mesophiles
Hyperthermophiles
Thermophiles

Explanation:

Mesophiles grow best at moderate temperatures (20–45°C), like human body temperature.

Q. Psychrophiles grow best at:
Cold temperatures (<15°C)
Neutral pH
Body temperature
High temperatures (>60°C)

Explanation:

Psychrophiles thrive at cold temperatures (below 15°C).

Q. Thermophiles grow best at:
Body temperature
High temperatures (45–80°C)
Cold temperatures
Low pH

Explanation:

Thermophiles thrive at high temperatures (45–80°C).

Q. Bacteria that require oxygen for growth are called:
Facultative anaerobes
Obligate anaerobes
Obligate aerobes
Microaerophiles

Explanation:

Obligate aerobes require oxygen; obligate anaerobes are killed by oxygen.

Q. Bacteria killed by oxygen are:
Aerotolerant anaerobes
Obligate anaerobes
Facultative anaerobes
Obligate aerobes

Explanation:

Obligate anaerobes cannot survive in the presence of oxygen.

Q. Facultative anaerobes:
Grow with or without oxygen
Require CO2
Are killed by oxygen
Require oxygen

Explanation:

Facultative anaerobes can grow with or without oxygen.

Q. Bacterial metabolism that uses oxygen as final electron acceptor is:
Aerobic respiration
Fermentation
Anaerobic respiration
Photosynthesis

Explanation:

Aerobic respiration uses oxygen as the final electron acceptor.

Q. Fermentation in bacteria produces:
Only water
Only oxygen
Only glucose
ATP without oxygen

Explanation:

Fermentation produces ATP without oxygen, generating products like lactic acid, ethanol, or acetic acid.

Q. Which bacteria are used in yogurt production?
E. coli and Salmonella
Mycobacterium and Corynebacterium
Clostridium and Bacillus
Lactobacillus and Streptococcus

Explanation:

Lactobacillus and Streptococcus species ferment milk into yogurt.

Q. Nitrogen-fixing bacteria convert:
Nitrate to N2
N2 to ammonia
Ammonia to N2
N2 to nitrate

Explanation:

Nitrogen-fixing bacteria (e.g., Rhizobium) convert atmospheric N2 into ammonia.

Q. Rhizobium bacteria form symbiotic relationships with:
Fish gills
Human skin
Animal intestines
Legume roots

Explanation:

Rhizobium forms nodules on legume roots for nitrogen fixation.

Q. Which is a selective medium for Gram-negative bacteria?
MacConkey agar
Nutrient agar
Blood agar
Chocolate agar

Explanation:

MacConkey agar inhibits Gram-positive bacteria and allows Gram-negative growth.

Q. Blood agar is classified as:
Defined medium
Minimal medium
Enriched and differential
Selective only

Explanation:

Blood agar is an enriched, differential medium showing hemolysis patterns.

Q. Autoclaving uses which combination for sterilization?
UV light
Filtration
High-pressure steam
Dry heat

Explanation:

Autoclaving uses high-pressure steam (121°C, 15 psi) for 15–20 minutes.

Q. Pasteurization uses:
High-pressure steam
UV light
Controlled heating to kill pathogens
Radiation

Explanation:

Pasteurization heats liquids (e.g., milk) to kill pathogens without sterilizing.

Q. A bacterial colony arises from:
A spore
A single cell
Multiple cells
A virus

Explanation:

Each colony arises from a single bacterial cell (or CFU — colony-forming unit).

Q. CFU stands for:
Cellular Function Unit
Cell Fusion Unit
Culture Fast Unit
Colony-Forming Unit

Explanation:

CFU stands for Colony-Forming Unit, a measure of viable bacterial numbers.

Q. Viable plate count measures:
Living bacteria
Bacterial DNA
Bacterial proteins
Total bacteria including dead

Explanation:

Viable plate count measures living (viable) bacteria that can form colonies.

Q. Antibiotic resistance can spread between bacteria via:
Spore formation
Horizontal gene transfer
Binary fission only
Capsule formation

Explanation:

Resistance spreads via horizontal gene transfer: conjugation, transformation, and transduction.

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