Bacterial growth Flashcards
Which scientist is credited with inventing the first microscope in 1684?
A) Louis Pasteur
B) Robert Koch
C) Antoni van Leeuwenhoek
D) Alexander Fleming
C
What is the primary requirement for bacterial metabolism and growth?
A) Nucleic acids only
B) Carbohydrates, amino acids, and lipids
C) Oxygen and light
D) Antibiotics
B
Which of the following is NOT a minimum requirement for bacterial growth?
A) Carbon
B) Nitrogen
C) Ions
D) Phospholipids
D
Which of the following bacteria is an obligate aerobe?
A) Clostridium perfringens
B) Mycobacterium tuberculosis
C) Escherichia coli
D) Helicobacter pylori
B
Which bacterial group can grow in both aerobic and anaerobic conditions?
A) Obligate aerobes
B) Obligate anaerobes
C) Facultative anaerobes
D) Microaerophiles
C
Which temperature classification includes most pathogenic bacteria?
A) Psychrophiles
B) Mesophiles
C) Thermophiles
D) Hyperthermophiles
B
What is the primary characteristic of the lag phase?
A) Rapid exponential growth
B) Nutrient depletion
C) Adaptation to a new environment
D) Cell death exceeds cell division
C
What happens in the stationary phase of bacterial growth?
A) The population continues growing exponentially
B) Nutrients become limited, leading to a balance of cell division and death
C) The bacterial population completely stops growing
D) Only dormant spores survive
B
During which phase are bacteria most susceptible to antibiotics?
A) Lag phase
B) Log (exponential) phase
C) Stationary phase
D) Death phase
B
The average bacterial generation time is:
A) 1-3 minutes
B) 1-3 hours
C) 24 hours
D) 1-3 days
B
What determines bacterial generation time?
A) The time it takes for one cell to divide
B) The duration of the stationary phase
C) The total time bacteria remain viable
D) The number of colonies in a culture
A
Which type of media allows growth of only specific bacteria?
A) Basic media
B) Differential media
C) Enrichment media
D) Selective media
D
What is the function of differential media?
A) It differentiates bacterial species based on metabolic activity
B) It promotes the growth of specific bacteria
C) It inhibits Gram-positive bacteria
D) It prevents contamination
A
What is the primary purpose of enrichment culture?
A) To detect antibiotic resistance
B) To increase the number of a specific bacterial species
C) To kill unwanted bacteria
D) To measure bacterial motility
B
Which of the following is a reducing agent used in anaerobic cultivation?
A) Thioglycolate
B) Peptone
C) Agar
D) Starch
A
What is measured at OD600 in spectrophotometry?
A) Bacterial DNA content
B) Optical density to estimate bacterial concentration
C) Antibiotic susceptibility
D) Bacterial motility
B
What is the purpose of the GasPak jar?
A) To provide oxygen for obligate aerobes
B) To measure bacterial motility
C) To create an anaerobic environment
D) To differentiate bacterial species
C
The pour plate method is used for:
A) Counting bacteria in liquid samples
B) Identifying bacterial species
C) Measuring bacterial motility
D) Observing bacterial conjugation
A
What is the advantage of using viable plate counts?
A) It detects both live and dead bacteria
B) It provides an immediate result
C) It only counts viable cells
D) It does not require incubation
D
Why does bacterial growth increase in number rather than size?
A) Bacteria have rigid cell walls preventing expansion
B) Bacteria rely on binary fission for reproduction
C) Nutrient limitations restrict size growth
D) All of the above
D
Which of the following best defines “generation time” in bacteria?
A) Time required for DNA replication
B) Time needed for a single bacterial cell to divide
C) Time taken for a bacterial population to stabilize
D) Time required for bacteria to produce enzymes
B
Which of the following is a metabolic by-product that can be used to classify bacteria?
A) Oxygen consumption
B) Nucleic acid production
C) Acid and gas formation
D) Binary fission rate
C
Why do obligate anaerobes die in the presence of oxygen?
A) They lack catalase and superoxide dismutase enzymes
B) Oxygen blocks ATP synthesis
C) Oxygen prevents binary fission
D) Oxygen destroys bacterial cell membranes
A
In which phase do bacteria adjust to a new environment before starting division?
A) Lag phase
B) Log phase
C) Stationary phase
D) Death phase
A
The death phase in bacterial growth is primarily due to:
A) Nutrient depletion and waste accumulation
B) Lack of binary fission
C) Increased oxygen concentration
D) Excess metabolic activity
A
What happens in the stationary phase of bacterial growth?
A) Cell division stops completely
B) Cell division equals the death rate
C) Cells become dormant but viable
D) Enzyme production ceases
B
Why are bacteria most susceptible to antibiotics during the log phase?
A) Cell division is at its highest
B) The bacterial genome is more exposed
C) Bacteria produce more toxins
D) Cells form endospores
A
Which of the following factors influences the rate of bacterial death during heat treatment?
A) Time of exposure
B) Temperature applied
C) Microbial load in the sample
D) All of the above
D
What does a differential medium do?
A) Supports the growth of all bacteria equally
B) Distinguishes bacteria based on metabolic properties
C) Selects for Gram-positive bacteria
D) Prevents contamination
B
Why is thioglycolate broth used in microbiology?
A) To differentiate between Gram-positive and Gram-negative bacteria
B) To determine bacterial oxygen requirements
C) To test for motility
D) To culture intracellular bacteria
B
