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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
Form spores
Transfer DNA
Become dormant

Explanation:

Binary fission is asexual reproduction producing two identical daughter cells.

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

Explanation:

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

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

Explanation:

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

Q. In the lag phase, bacteria:
Adapt without dividing
Die
Divide rapidly
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
Growth rate equals death rate
All bacteria die

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 for population to double
Time to transfer DNA
Time to form spores

Explanation:

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

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

Explanation:

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

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

Explanation:

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

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

Explanation:

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

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

Explanation:

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

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

Explanation:

Obligate anaerobes cannot survive in the presence of oxygen.

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

Explanation:

Facultative anaerobes can grow with or without oxygen.

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

Explanation:

Aerobic respiration uses oxygen as the final electron acceptor.

Q. Fermentation in bacteria produces:
Only glucose
Only water
Only oxygen
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?
Mycobacterium and Corynebacterium
E. coli and Salmonella
Lactobacillus and Streptococcus
Clostridium and Bacillus

Explanation:

Lactobacillus and Streptococcus species ferment milk into yogurt.

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

Explanation:

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

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

Explanation:

Rhizobium forms nodules on legume roots for nitrogen fixation.

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

Explanation:

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

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

Explanation:

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

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

Explanation:

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

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

Explanation:

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

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

Explanation:

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

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

Explanation:

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

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

Explanation:

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

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

Explanation:

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

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