Microorganisms

Question 1

In what ways can you grow/culture bacteria?

Answer 1

• Nutrient broth solution

- Colonies on an agar plate

Question 2

How often can bacteria replicate?

Answer 2

Approximately every 20 mins

Question 3

How do bacteria replicate?

Answer 3

Binary fission

Question 4

How can microorganisms grow in a nutrient broth?

Answer 4

The liquid/gel provides al the nutrients the bacteria needs to grow successfully, including:

• Carbohydrates for energy
• Nitrogen for protein synthesis
• Minerals

Question 5

How are agar plates created?

Answer 5

By pouring hot molten agar into sterile petri dishes and allowing it to set

Question 6

What are aseptic techniques?

Answer 6

Procedures to prevent contamination from pathogens

Question 7

What are aseptic techniques?

Answer 7

Procedures to prevent contamination from pathogens

Question 8

Why is it important to use aseptic techniques on all apparatus when culturing microorganisms?

Answer 8

To prevent contamination from skin, air, soil, and water. This kills and prevents entry of unwanted bacteria

Question 9

What aseptic techniques are used in the culturing of microorganisms?

Answer 9

Flames
Temperature
Boiling
Lids

Question 10

How is management of lids used as an aseptic technique?

Answer 10

To prevent air from getting into the Petri dish, the lid must be quickly removed and replaced when transferring bacteria to the agar using the inoculating loop. Lid should be taped on and the dish should be stored upside down to prevent condensation forming on the lid and then dripping onto the agar.

Question 11

How is boiling used as an aseptic technique?

Answer 11

Solutions and agar must be boiled for sterilisation

Question 12

How is management of temperature used as an aseptic technique?

Answer 12

In schools the maximum temperature at which cultures should be incubated is 25’C which reduces the risk of harmful bacteria growing.

Question 13

How are flames used as an aseptic technique

Answer 13

Inoculation loops must be passed through a flame for sterilisation

Question 14

What can cultures of bacteria be used for?

Answer 14

To investigate effects of antibiotics and disinfectants

Question 15

What is the inoculating loop used for?

Answer 15

To transfer bacteria onto the agar plate

Question 16

How would you know if a sample has been contaminated?

Answer 16

If there are colonies of different colours observed on the Petri dish

Question 17

Why shouldn’t we seal the Petri dish all the way around before storing?

Answer 17

We want oxygen to get in so harmful anaerobic bacteria doesn’t grow

Question 18

What effect does temperature have on the growth and development of bacteria?

Answer 18

Cell metabolism (chemical reactions) in bacteria is controlled by enzymes.
Increasing temp. up to 37 degrees speeds up rate of reactions as this is the optimum temperature for the enzymes to function
Higher than 37 degrees and the enzymes denature (e.g. cooking food kills bacteria)
Low temperatures do not kill bacteria but considerably slow down/stops reproduction of bacteria depending on how cold it is  (e.g. fridges slow it down at 4 degrees, freezers stop it at -20 but does not kill them)

Question 19

What equation would be used to calculate the areas of bacteria killed by an antiseptic/antibiotic, and what would this indicate?

Answer 19

A = πr2
Area = π x radius2
The largest area cleared indicates the most effective antibiotic/antiseptic.

Question 20

How can a future population of bacteria be estimated?

Answer 20

By multiplying the current population by two for every mean division time (time it takes for the bacteria to divide) that passes

1. Calculate how many times the bacteria divide in 6h
   e. g. if a bacteria divides every 20m it will divide 3x each hour. If it grows for 6h, this will be 3x6=18 times
2. Calculate number of bacteria in population
   Use equation:
   Number of bacteria at beginning of growth period x 2^number of divisions

Question 21

How can we test the effectiveness of an antibiotic?

Answer 21

By applying antibiotic-containing paper disks to agar plates incubated with a species of bacteria.
If the antibiotic stops the bacteria from growing or kills the bacteria there will be an area around the disk where the bacteria have not grown enough to be visible called a ZONE OF INHIBITION

Question 22

What is a zone of inhibition?

Answer 22

The area around a sample of an antibiotic where bacteria hasn’t been able to grow

Question 23

How would you perform an experiment investigating the effect of antibiotics on bacterial growth?

Answer 23

1. Flame forceps and use them to pick up a paper disk and dip it into antibiotic A
2. Allow them to dry for 5 minutes on an open, sterile Petri dish, next to a lit Bunsen burner
3. Repeat steps for antibiotics B, C, and D
4. Turn an agar plate already prepared and seeded with bacteria upside down and divide the base into quarters laelled A, B, C, and D
5. Flame forceps again and pick up antibiotic disk A. Raise the lid of the Petri dish and place the disk on the agar in the centre of section A
6. Repeat step for other disks
7. Tape lid securely and incubate upside down for 2-3 days at 20-25C
8. Record width of each clear zone around the antimicrobials

Question 24

What factors affect the rate at which populations of bacteria grow?

Answer 24

Moisture availability - Bacterial growth is usually fastest in moist conditions (which is why food is sealed in dry conditions)
Temperature - Growth rates are fastest in warm temperatures

Question 25

What is penicillium?

Answer 25

A fungus that produces the substance penicillin

Question 26

What are the ideal conditions for penicillium to grow in?

Answer 26

Temp of 23-28C
Slightly acidic pH of 6.5
Availability of nutrients and oxygen

Question 27

Where is penicillium grown?

Answer 27

In large metal fermenters

Question 28

What features does a fermenter have?

Answer 28

Steam inlet
Nutrient inlet
Water jacket with cooling water
Air inlet
Filter on air inlet
Stirring paddles
pH probe and intake valve for acid and alkali

Question 29

What is the purpose of a steam inlet in a fermenter?

Answer 29

An aseptic precaution to prevent contamination by unwanted microorganisms

Question 30

What is the purpose of a water jacket in a fermenter?

Answer 30

Keeps the temperature inside constant so the optimum temp of 23-25C is maintained

Question 31

What is the purpose of an air inlet in a fermenter?

Answer 31

Provides a source of oxygen which penicillium needs for aerobic respiration

Question 32

What is the purpose of a filter on the air inlet in a fermenter?

Answer 32

To stop microorganisms getting inside the fermenter to prevent contamination

Question 33

What is the purpose of a stirring paddles in a fermenter?

Answer 33

To keep the mixture inside the fermenter agitated (stirred) and keeps oxygen and nutrients distributed evenly

Question 34

What is the purpose of a pH probe in a fermenter?

Answer 34

To maintain an ideal pH of 6.5

Question 35

How long is penicillium left in the fermenter?

Answer 35

Around 200 hours

Question 36

What happens to penicillium once it is removed from the fermenter?

Answer 36

The liquid is removed and filtered, removing fungal cells and leaving the product penicillin which will need to be treated before use