Culturing microorganisms - Cell Biology

Question 1

How do prokaryotic cells reproduce?

Answer 1

Binary fission

Question 2

Explain binary fission in 5 steps

Answer 2

1. Circular DNA and plasmids replicate
2. Cell gets bigger
3. Circular DNA goes to opposite ends of cell
4. Cytoplasm begins to dicde and new cell walls begin to form
5. Cytoplasm divides and 2 daughter cells are produced. Each cell has 1 copu of the ciruclar DNA but can have a variable number of copies of the plasmids

Question 3

What does bacteria need to reproduce and what is the min time it takes?

Answer 3

Needs warm environment and lots of nutrients, can take as little as 20 min to replicate. If environment becomes unfavourable, cells stop dividing and die

Question 4

What is the mean division time?

Answer 4

Average amount of time it takes for 2 bacterial cell to divide

Question 5

What is the formula for mean division time?

Answer 5

Number of bacteria at start X 2ⁿᵒ. ᵈᶦᵛᶦˢᶦᵒⁿˢ

Question 6

Where is bacteria grown in a lab?

Answer 6

• Broth solution
• Agar gel plate

Question 7

Why should petri dishes and culture media be sterilised before use?

Answer 7

To kill the bacteria already on them, otherwise they would grow to contaminate the culture to be studied

Question 8

What does a culture medium have?

Answer 8

• Carbs
• Minerals
• Proteins
• Vitamins

Question 9

Why should inoculating loops be used to transfer microorganisms to the media, why should they be sterilised by passing them through a flame?

Answer 9

Avoids contamination and improves accuracy

Question 10

Why should the lid of the Petri dish be taped and upside down?

Answer 10

Taped = stops microorganisms from the air getting in
Upside down =To stop drops of condensation falling onto the agar surface disrupting the colonies

Question 11

Why should cultures not be above 25 in schools?

Answer 11

Harmful pathogens can grow

Question 12

What is the zone of inhibition?

Answer 12

Where there is no bacteria

Question 13

Method?

Answer 13

1. Make agar plate into sections
2. Flame lid of the bottle of bacteria after opening
3. Use pipette to get 1ml of the bacteria solution
4. Minimum time and opening to squirt out solution
5. Use inoculating loop to spread out bacteria
6. Label sections on lid to know what antibiotics you’ll use
7. Soak paper disc into liquid
8. Use tape to seal lid and store upside down
9. Disinfect table using alcohol
10. Measure zone of inhibition using formula