Lab 3

Question 1

Describe Bacillus stearothermophilus

Answer 1

Thermophile (hot pools)

Question 2

Describe Bacillus subtilis

Answer 2

Increased UV tolerance (Soil)

Question 3

Describe E. coli

Answer 3

(lower gut)
Mesophile
Non/mild halophile
neutral pH

Question 4

Listenella anguillarum

Answer 4

Psychotroph, moderate halophile, alkaphile (marine)

Question 5

Staphylococcus epidermidis

Answer 5

Extreme halophile (Skin)

Question 6

Describe Lactobacillus

Answer 6

Acidophile (upper gut)

Question 7

What morphology do most endospore-formers share

Answer 7

Gran (+) rods (irregular staining due to endospore formation

Question 8

What would it mean if the negative control had no colonies

Answer 8

No contamination
- Dilutant was sterile
- Good aseptic technique

Question 9

What would it mean if the negative control had a few surface colonies

Answer 9

Contamination after plating of agar
- Poor aseptic technique

Question 10

What would it mean if the negative control had alot of surface and subsurface colonies

Answer 10

Contamination during pouring
- Dilutant and/or media contaminated

Question 11

Describe the results of the competition experiment

Answer 11

S. equi can’t make its own metabolites so only grows on TBH medium as it is nutrient rich - won’t grow on minimal salt
E. coli can produce its own and will therefore grow on both media - is better at competing for nutrients

Question 12

Describe the term ubiquitous

Answer 12

No environment on earth you wouldn’t find microorganisms growing

Question 13

Describe a psychrophiles

Answer 13

0-20 degrees
- important in food preservations
- Listeria monocytogenes (4 degrees)

Question 14

Describe mesophiles

Answer 14

Prefer 20-45 degrees
- soil organisms and all human pathogens
- S. aureus and E. coli

Question 15

Describe thermophiles

Answer 15

Prefers 45-80 degrees
- thermal pools and some soils in summer
- thermus aquaticus

Question 16

Describe hyper thermophiles

Answer 16

Prefer >80 degrees
- Hot springs and marine hydrothermal vent
- Pyrolobus fumari (above 90)

Question 17

Can bacteria last outside of their usual ranges

Answer 17

Yes but they may not be able to increase in numbers

Question 18

What are thermoduric organisms

Answer 18

Organisms that can survive at high temperatures but are unable to grow
- endospore formers

Question 19

Why is UV light dangerous

Answer 19

Short wavelength and high energy

Question 20

What is the wavelength of UV radiation

Answer 20

260 nm - most effectively absorbed by DNA

Question 21

What is the primary mechanism of UV damage

Answer 21

Formation of thymine dimes in DNA

Question 22

Why did we remove the lids of the plate when exposing to UV light

Answer 22

UV has a low penetration

Question 23

Why do we cover the plates after exposing them to UV

Answer 23

To block photoreactions - repairs DNA damage when exposed to light

Question 24

Is acidity or alkalinity more common in nature

Answer 24

Acidity is more common
- develops in oxidising environments (biosphere predominantly aerobic)

Question 25

How does sulphuric acid arise

Answer 25

From the oxidation of sulphides (H2S,FeS2) - common in volcanic and geothermal areas, bogs swamps and acid soils

Question 26

What causes acid rain

Answer 26

Combustion of sulphurous fossil fuels

Question 27

Why might lakes become acidic during acid rain

Answer 27

When they have little buffering capacity (4.0pH)

Question 28

How do leachates come about

Answer 28

Acid mine drainage (sulphides from coal) - 2-3 pH

Question 29

What is the optimal pH for Listonella

Answer 29

9.0 - alkaphile - moderate halophile (marine environment)

Question 30

What is the optimal pH for E. coli

Answer 30

7.0 - neutral pH (lower gut environment)

Question 31

What is the optimal pH for Lactobacillus

Answer 31

5.0 - acidophile (gut environment)