A culture is a method of growing microorganisms in controlled conditions to obtain enough individuals for measurement and investigation.

What is a colony of bacteria in the context of culturing microorganisms?

A colony is a visible group of identical bacterial cells that have reproduced from a single original cell, typically seen when grown on agar gel.

Microorganisms require , oxygen, optimum pH, and favourable to grow.

Microorganisms require nutrients , oxygen, optimum pH, and favourable temperature to grow.

True or False? Sterilising equipment before culturing bacteria is unnecessary if the bacteria are not harmful.

False. Sterilising equipment is essential to prevent contamination and ensure reliable results, regardless of whether the bacteria are harmful.

A selective medium is a nutrient growth medium designed to promote the growth of certain microorganisms while inhibiting others, helping to identify or isolate specific strains.

What is the purpose of an inoculation loop in microbiology?

An inoculation loop is a sterilised tool used to transfer microorganisms between growth media, such as from a liquid culture to an agar gel.

To avoid contamination, the new growth medium should be or covered, and clearly .

To avoid contamination, the new growth medium should be sealed or covered, and clearly labelled .

How can you obtain a pure culture of a single type of microorganism?

A pure culture can be obtained by isolating the specific microorganism, using selective or indicator media, and providing conditions such as aerobic or anaerobic environments that favour the desired microorganism.

A haemocytometer is a microscope slide with a rectangular chamber marked with grid lines, used to count single-celled microorganisms in a known volume of liquid.

Why is trypan blue used when counting cells with a haemocytometer?

Trypan blue is used because it stains dead cells blue , allowing the investigator to only count living cells .

Counting cells using a haemocytometer involves filling the chamber with nutrient broth and counting the number of living cells in the four squares.

Counting cells using a haemocytometer involves filling the chamber with stained nutrient broth and counting the number of living cells in the four corner squares.

What is the calculation used to estimate the number of cells per ml of nutrient broth using a haemocytometer?

The calculation is: No. of cells per ml = mean cell count × dilution factor × 10⁴

Dilution plating is a technique where a microbial culture is serially diluted and plated onto agar to allow counting of individual colonies, each representing one viable cell .

How is the total viable cell count calculated in dilution plating?

The total viable cell count is calculated by multiplying the number of colonies by the dilution factor .

In the measurement of fungal growth, a larger mean indicates a greater amount of fungal .

In the measurement of fungal growth, a larger mean diameter indicates a greater amount of fungal growth .

Turbidimetry is a form of colorimetry that measures the turbidity (cloudiness) of a solution to estimate the number of cells present.

How can a calibration curve be used in optical methods to estimate cell count?

A calibration curve is created by plotting turbidity against cell count from control samples; it can then be used to estimate the cell count of unknown samples by measuring their turbidity and referencing the curve.

A is a mass of identical cells formed by a single microorganism reproducing on agar, and each can be counted as one .

A colony is a mass of identical cells formed by a single microorganism reproducing on agar, and each can be counted as one viable cell .

How can the mass method be used to measure the growth of microorganisms?

A sample of the culture is filtered or centrifuged, dried and weighed to find its dry mass ; an increase in dry mass over time indicates growth of the microorganism population.

Binary fission is the process by which a bacterial cell divides into two identical daughter cells , each containing a copy of the parent cell’s circular DNA and plasmids.

During binary fission, what happens to the plasmids in a bacterial cell?

Any plasmids present in the bacterial cell undergo DNA replication so that they can be distributed to the daughter cells during binary fission.

The population size during the phase increases slowly as bacteria adjust to their environment.

The population size during the lag phase increases slowly as bacteria adjust to their environment.

What is the difference between the exponential and stationary phases of the bacterial growth curve?

During the exponential phase , the population doubles rapidly due to abundant resources, while in the stationary phase , growth is limited and the death rate equals the reproduction rate, causing the population size to level off.

A logarithmic scale is a way of displaying numerical data over a very wide range of values in a compact form, where each unit increase on the scale corresponds to a multiplication by a base number, such as 10.

True or False? On a logarithmic scale graph, the intervals between values on the y-axis are equal.

False. On a logarithmic scale graph, the intervals between values on the y-axis are not equal , as each step represents a multiplication by the base number.

The phase of the bacterial growth curve where the death rate exceeds the rate of reproduction is called the phase.

The phase of the bacterial growth curve where the death rate exceeds the rate of reproduction is called the death phase.

Exponential growth rate constant (k)

The exponential growth rate constant (k) is the number of times the population of organisms doubles in a given time period.

What formula is used to calculate the number of bacteria in a population at time t during exponential growth?

The formula is Nₜ = N₀ × 2^(kt) , where Nₜ is the number at time t, N₀ is the initial number, k is the growth rate constant, and t is time.

During the phase, the bacterial population doubles with each division and grows rapidly.

During the exponential phase, the bacterial population doubles with each division and grows rapidly.

Turbidity is the cloudiness of a solution , often caused by suspended particles such as microorganisms.

What is measured as an indicator of yeast growth in a liquid culture?

The change in turbidity of the yeast solution is measured as an indicator of yeast growth in a liquid culture.

A colorimeter is used to measure the of a yeast solution, which reflects the growth of microorganisms.

A colorimeter is used to measure the absorbance of a yeast solution, which reflects the growth of microorganisms.

What is the purpose of adding a cotton wool stopper to the conical flask after inoculating with yeast?

The cotton wool stopper is used to prevent contamination of the culture by microorganisms in the air.

After inoculation, the flask should be incubated at °C for safe laboratory practice.

After inoculation, the flask should be incubated at 20 °C for safe laboratory practice.

True or False? Aseptic techniques are not necessary when transferring yeast to the glucose solution.

False. Aseptic techniques are essential to prevent contamination during the transfer of yeast to the glucose solution.

Liquid culture medium

A liquid culture medium is a solution, such as glucose solution, that supports the growth of microorganisms .

Why is a blank cuvette with plain glucose solution used to calibrate the colorimeter?

A blank cuvette is used to reset the colorimeter to zero , ensuring that only the turbidity due to yeast growth is measured.

What is a haemocytometer ?

A haemocytometer is a specialised microscope slide used to count the number of cells in a given volume of liquid.

True or False? Turbidity measurements only indicate the number of living cells in the medium.

False. Turbidity measurements are mainly a measure of living cells, but can also be affected by dead cells and other suspended particles .

A prokaryote is a single-celled organism lacking a nucleus and membrane-bound organelles, such as a bacterium.

What is the function of the slime capsule in bacteria?

The slime capsule helps protect bacteria from drying out and from attack by the host's immune system.

Bacterial cell walls contain (murein), a polymer of sugars and peptides.

Bacterial cell walls contain peptidoglycan (murein), a polymer of sugars and peptides.

Which structures allow bacteria to move and attach to surfaces?

Bacteria use flagella to move and pili to attach to surfaces or transfer genes.

A virus is a non-cellular infectious particle consisting of a nucleic acid core and a protein coat, and sometimes a lipid envelope.

True or False? All viruses possess a lipid envelope.

False. Only some viruses have a lipid envelope , which is formed from the host cell membrane.

Retroviruses such as HIV contain as genetic material and use the enzyme to make DNA from it.

Retroviruses such as HIV contain RNA as genetic material and use the enzyme reverse transcriptase to make DNA from it.

How do bacteriophages infect bacterial cells?

Bacteriophages inject their genetic material into bacteria to infect them.

Plant viruses often use a such as an insect to breach the cell wall.

Plant viruses often use a vector such as an insect to breach the cell wall.

What is the difference between the lytic and lysogenic pathways in viral infection?

The lytic pathway involves immediate production of new viruses and cell lysis, while the lysogenic pathway involves viral DNA integrating into host DNA and remaining dormant for a period.

Latency is the period during which viral DNA is integrated into the host genome but is not actively producing new viruses.

True or False? Cell lysis always results in disease.

False. Cell lysis releases many new viruses and typically results in disease symptoms, but it does not always cause disease.

International A Level (IAL)BiologyEdexcelFlashcards6. Microbiology, Immunity & ForensicsMicrobiology

Microbiology (Edexcel International A Level (IAL) Biology): Flashcards

Exam code: YBI11

1/52

0Still learning

Know0

FrontCulturing Microorganisms
Culture

Was this flashcard helpful?

Cards in this collection (52)

Culture
A culture is a method of growing microorganisms in controlled conditions to obtain enough individuals for measurement and investigation.
What is a colony of bacteria in the context of culturing microorganisms?
A colony is a visible group of identical bacterial cells that have reproduced from a single original cell, typically seen when grown on agar gel.
Microorganisms require , oxygen, optimum pH, and favourable to grow.
Microorganisms require nutrients, oxygen, optimum pH, and favourable temperature to grow.
True or False?
Sterilising equipment before culturing bacteria is unnecessary if the bacteria are not harmful.
False.
Sterilising equipment is essential to prevent contamination and ensure reliable results, regardless of whether the bacteria are harmful.
Selective medium
A selective medium is a nutrient growth medium designed to promote the growth of certain microorganisms while inhibiting others, helping to identify or isolate specific strains.
What is the purpose of an inoculation loop in microbiology?
An inoculation loop is a sterilised tool used to transfer microorganisms between growth media, such as from a liquid culture to an agar gel.
To avoid contamination, the new growth medium should be or covered, and clearly .
To avoid contamination, the new growth medium should be sealed or covered, and clearly labelled.
How can you obtain a pure culture of a single type of microorganism?
A pure culture can be obtained by isolating the specific microorganism, using selective or indicator media, and providing conditions such as aerobic or anaerobic environments that favour the desired microorganism.
Haemocytometer
A haemocytometer is a microscope slide with a rectangular chamber marked with grid lines, used to count single-celled microorganisms in a known volume of liquid.
Why is trypan blue used when counting cells with a haemocytometer?
Trypan blue is used because it stains dead cells blue, allowing the investigator to only count living cells.
Counting cells using a haemocytometer involves filling the chamber with nutrient broth and counting the number of living cells in the four squares.
Counting cells using a haemocytometer involves filling the chamber with stained nutrient broth and counting the number of living cells in the four corner squares.
What is the calculation used to estimate the number of cells per ml of nutrient broth using a haemocytometer?
The calculation is: No. of cells per ml = mean cell count × dilution factor × 10⁴
Dilution plating
Dilution plating is a technique where a microbial culture is serially diluted and plated onto agar to allow counting of individual colonies, each representing one viable cell.
How is the total viable cell count calculated in dilution plating?
The total viable cell count is calculated by multiplying the number of colonies by the dilution factor.
In the measurement of fungal growth, a larger mean indicates a greater amount of fungal .
In the measurement of fungal growth, a larger mean diameter indicates a greater amount of fungal growth.
Turbidimetry
Turbidimetry is a form of colorimetry that measures the turbidity (cloudiness) of a solution to estimate the number of cells present.
How can a calibration curve be used in optical methods to estimate cell count?
A calibration curve is created by plotting turbidity against cell count from control samples; it can then be used to estimate the cell count of unknown samples by measuring their turbidity and referencing the curve.
A is a mass of identical cells formed by a single microorganism reproducing on agar, and each can be counted as one .
A colony is a mass of identical cells formed by a single microorganism reproducing on agar, and each can be counted as one viable cell.
How can the mass method be used to measure the growth of microorganisms?
A sample of the culture is filtered or centrifuged, dried and weighed to find its dry mass; an increase in dry mass over time indicates growth of the microorganism population.
Binary fission
Binary fission is the process by which a bacterial cell divides into two identical daughter cells, each containing a copy of the parent cell’s circular DNA and plasmids.
During binary fission, what happens to the plasmids in a bacterial cell?
Any plasmids present in the bacterial cell undergo DNA replication so that they can be distributed to the daughter cells during binary fission.
The population size during the phase increases slowly as bacteria adjust to their environment.
The population size during the lag phase increases slowly as bacteria adjust to their environment.
What is the difference between the exponential and stationary phases of the bacterial growth curve?
During the exponential phase, the population doubles rapidly due to abundant resources, while in the stationary phase, growth is limited and the death rate equals the reproduction rate, causing the population size to level off.
Logarithmic scale
A logarithmic scale is a way of displaying numerical data over a very wide range of values in a compact form, where each unit increase on the scale corresponds to a multiplication by a base number, such as 10.
True or False?
On a logarithmic scale graph, the intervals between values on the y-axis are equal.
False.
On a logarithmic scale graph, the intervals between values on the y-axis are not equal, as each step represents a multiplication by the base number.
The phase of the bacterial growth curve where the death rate exceeds the rate of reproduction is called the phase.
The phase of the bacterial growth curve where the death rate exceeds the rate of reproduction is called the death phase.
Exponential growth rate constant (k)
The exponential growth rate constant (k) is the number of times the population of organisms doubles in a given time period.
What formula is used to calculate the number of bacteria in a population at time t during exponential growth?
The formula is Nₜ = N₀ × 2^(kt), where Nₜ is the number at time t, N₀ is the initial number, k is the growth rate constant, and t is time.
During the phase, the bacterial population doubles with each division and grows rapidly.
During the exponential phase, the bacterial population doubles with each division and grows rapidly.
Turbidity
Turbidity is the cloudiness of a solution, often caused by suspended particles such as microorganisms.
What is measured as an indicator of yeast growth in a liquid culture?
The change in turbidity of the yeast solution is measured as an indicator of yeast growth in a liquid culture.
A colorimeter is used to measure the of a yeast solution, which reflects the growth of microorganisms.
A colorimeter is used to measure the absorbance of a yeast solution, which reflects the growth of microorganisms.
What is the purpose of adding a cotton wool stopper to the conical flask after inoculating with yeast?
The cotton wool stopper is used to prevent contamination of the culture by microorganisms in the air.
After inoculation, the flask should be incubated at °C for safe laboratory practice.
After inoculation, the flask should be incubated at 20 °C for safe laboratory practice.
True or False?
Aseptic techniques are not necessary when transferring yeast to the glucose solution.
False.
Aseptic techniques are essential to prevent contamination during the transfer of yeast to the glucose solution.
Liquid culture medium
A liquid culture medium is a solution, such as glucose solution, that supports the growth of microorganisms.
Why is a blank cuvette with plain glucose solution used to calibrate the colorimeter?
A blank cuvette is used to reset the colorimeter to zero, ensuring that only the turbidity due to yeast growth is measured.
What is a haemocytometer?
A haemocytometer is a specialised microscope slide used to count the number of cells in a given volume of liquid.
True or False?
Turbidity measurements only indicate the number of living cells in the medium.
False.
Turbidity measurements are mainly a measure of living cells, but can also be affected by dead cells and other suspended particles.
Prokaryote
A prokaryote is a single-celled organism lacking a nucleus and membrane-bound organelles, such as a bacterium.
What is the function of the slime capsule in bacteria?
The slime capsule helps protect bacteria from drying out and from attack by the host's immune system.
Bacterial cell walls contain (murein), a polymer of sugars and peptides.
Bacterial cell walls contain peptidoglycan (murein), a polymer of sugars and peptides.
Which structures allow bacteria to move and attach to surfaces?
Bacteria use flagella to move and pili to attach to surfaces or transfer genes.
Virus
A virus is a non-cellular infectious particle consisting of a nucleic acid core and a protein coat, and sometimes a lipid envelope.
True or False?
All viruses possess a lipid envelope.
False.
Only some viruses have a lipid envelope, which is formed from the host cell membrane.
Retroviruses such as HIV contain as genetic material and use the enzyme to make DNA from it.
Retroviruses such as HIV contain RNA as genetic material and use the enzyme reverse transcriptase to make DNA from it.
How do bacteriophages infect bacterial cells?
Bacteriophages inject their genetic material into bacteria to infect them.
Plant viruses often use a such as an insect to breach the cell wall.
Plant viruses often use a vector such as an insect to breach the cell wall.
What is the difference between the lytic and lysogenic pathways in viral infection?
The lytic pathway involves immediate production of new viruses and cell lysis, while the lysogenic pathway involves viral DNA integrating into host DNA and remaining dormant for a period.
Latency
Latency is the period during which viral DNA is integrated into the host genome but is not actively producing new viruses.
True or False?
Cell lysis always results in disease.
False.
Cell lysis releases many new viruses and typically results in disease symptoms, but it does not always cause disease.
Compare the structure of the example viruses HIV, Ebola, tobacco mosaic virus (TMV) and lambda phage (λ phage).
All four have a protein capsid enclosing their nucleic acid. HIV, Ebola and TMV contain RNA, whereas lambda phage contains DNA. HIV and Ebola also have a lipid envelope, while TMV and lambda phage do not.

Sign up to unlock flashcards

By signing up you agree to our Terms and Privacy Policy

Previous:Environmental BiologyNext:Immunity