Microbiology - Finished

Question 1

What is the definition of microbiology?

Answer 1

The study of organisms that are too small to be seen clearly without the use of a microscope

Question 2

What are the 3 main shapes of bacteria?

Answer 2

Round (coccus)
Rod shaped (basillus)
Spiral (spirillium)

Question 3

What colour do gram positive bacteria stain?

Answer 3

Purple

Question 4

What colour do gram negative bacteria stain?

Answer 4

Red

Question 5

What processes are involved in gram staining?

Answer 5

Application of crystal violet
Application of iodine
Alcohol wash
Application of saffarin

Question 6

Why do the different bacteria stain differently?

Answer 6

The different staining properties are due to the differenve in the chemical composition of their cell walls. The Gram negative bacteria have a more complex wall structure

Question 7

Which bacteria does penecillin act on?

Answer 7

Gram positive bacteria
Both bacteria have cell walls made of murein however gram negative bacteria have an additional outerlayer of lipopolysaccharide. Penicillin acts on the murein wall layer and makes it sstructurally weak.

Question 8

What conditions are needed to grow bacteria?

Answer 8

• Water
• Nutrients (in medium)
  organic form of carbon (usually glucose)
  nitrogen
  Growth factors e.g. vitamins/minerals
• Particular pH/temperature
• Presence/absence of oxygen

Question 9

What are obligate aerobes

Answer 9

Bacteria that can only survive in the presence of oxygen

Question 10

What type of bacteria survives in both the presence and absence of oxygen (but grows better better with oxygen)?

Answer 10

Facultative anaerobes

Question 11

What are obligate anaerobes?

Answer 11

Only survives in the absence of oxygen

Question 12

What condition do pathogenic bacteria grow best?

Answer 12

anaerobic

Question 13

What is aseptic technique?

Answer 13

Use of sterilized equiptment and methods that prevent contamination of culture or environment with unwanted organisms.

Question 14

What is involved in aseptic technique?

Answer 14

• Sterilization
  Autoclave equiptment to kill bacteria & endospores
  Heat innocluating loops untill it glows red
  Flame mouth of glass tubes and bottles
• After Sterilization - Prevent contamination
  Do NOT but culture bottle cap on to the bench
  Use of sterile air supply - Working in a sterile cabinet/working near a bunsen burner for updraft
• Heat labile plastics are iradicated

Question 15

What is sterilization?

Answer 15

Removal or distruction of all living organisms and theri spores

Question 16

What are the 2 methods of counting bacteria?

Answer 16

Total cell count = number of living + dead bacteria cells

Viable cell count = number of living bacterial cells

Question 17

what do you do to find a viable cell count?

Answer 17

Take a 1cm3 sample from your source and place it in your petri dish using aseptic technique.
Incubate for a day at 25C
Count how many colonies have appeared. - ASSUME ONE CELL GIVES WAY TO ONE COLONY

Question 18

What is one limitation of this method for finding a viable cell count?

Answer 18

Does not take clumping into account whic could cause an underestimation of the actual number of living bacteria present.

Question 19

What happens if there are too many bacteria on the dish for you to count?

Answer 19

Dilute the sample. Dilutions are usually carried out in 10 fold (1cm into 9cm) or 100 fold (1cm into 99cm / 0.1cm into 9.9cm)
use around 3 dilutions for each sample, taking the next sample out of the tets tube before.
Number of bacteria per cm in original sample = no. of colonies x dilution factor

Question 20

What is Industrial Fermentation?

Answer 20

anaerobic respiration in yeast

Large scale culturaling of bacterial and fungal cells in huge tanks known as industrial fermenters.

Question 21

Why is it good to culture bacteria and fungus in large batches?

Answer 21

The cells can produce useful products such as alcohol, biogas, insulin & antibiotics

Question 22

What is the first main principle of industrial fermentation?

Answer 22

A pure culture of the organism is needed for the formation of a pure product.
Maintain purity by:
- Sterilized vessel & growth medium
- Filters to prevent contamination
- Aseptic conditions & handling required

Question 23

What is th secnd main principle of industrial fermentation?

Answer 23

Organism must be supplied with suitable conditons for growth (usually without comppetition) fr maximum efficiency.
To provide suitable growth conditions:
- Forced aeration - provide enough oxygen for maximum growth and mix culture
- Spargers improve aeration by dispersing are as bubbles through meduim
- Mixing devices such as impellers
- Temperature must be monitored - water jacket removes excess heat produced by respiration
- Temperature & pH monitors

Question 24

What produces penecillin?

Answer 24

A species of fungus known as Penicillium Notatum

Question 25

How is Penicillium Notatum grown?

Answer 25

Using a batch culture

Question 26

What is Batch Culture?

Answer 26

In a batch Culture:

• All of the nutrients are added at the start of the culture process
• No microoganisms are added or removed during the incubation process
• The product is harvested at the end of the incubation process

Question 27

What is continuous culture?

Answer 27

Where nutrients are added and cells harvested at a continuous rate.

Question 28

How does the fungus produce penicillin?

Answer 28

Produced after the Growth(log) phase, when glucose is depleted. This reflects the need for the fungus (when the fungus is free living) to reduce competition when nutreit sources are depleted. It would normally release penicillin to kill off all of its competitors

Question 29

How is the penicillin removed?

Answer 29

The fungal mycelium is removed by filtration of the culture fluid and the antibiotic is purified from the residual liquid.