Lab 3 Flashcards
(31 cards)
Describe Bacillus stearothermophilus
Thermophile (hot pools)
Describe Bacillus subtilis
Increased UV tolerance (Soil)
Describe E. coli
(lower gut)
Mesophile
Non/mild halophile
neutral pH
Listenella anguillarum
Psychotroph, moderate halophile, alkaphile (marine)
Staphylococcus epidermidis
Extreme halophile (Skin)
Describe Lactobacillus
Acidophile (upper gut)
What morphology do most endospore-formers share
Gran (+) rods (irregular staining due to endospore formation
What would it mean if the negative control had no colonies
No contamination
- Dilutant was sterile
- Good aseptic technique
What would it mean if the negative control had a few surface colonies
Contamination after plating of agar
- Poor aseptic technique
What would it mean if the negative control had alot of surface and subsurface colonies
Contamination during pouring
- Dilutant and/or media contaminated
Describe the results of the competition experiment
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
Describe the term ubiquitous
No environment on earth you wouldn’t find microorganisms growing
Describe a psychrophiles
0-20 degrees
- important in food preservations
- Listeria monocytogenes (4 degrees)
Describe mesophiles
Prefer 20-45 degrees
- soil organisms and all human pathogens
- S. aureus and E. coli
Describe thermophiles
Prefers 45-80 degrees
- thermal pools and some soils in summer
- thermus aquaticus
Describe hyper thermophiles
Prefer >80 degrees
- Hot springs and marine hydrothermal vent
- Pyrolobus fumari (above 90)
Can bacteria last outside of their usual ranges
Yes but they may not be able to increase in numbers
What are thermoduric organisms
Organisms that can survive at high temperatures but are unable to grow
- endospore formers
Why is UV light dangerous
Short wavelength and high energy
What is the wavelength of UV radiation
260 nm - most effectively absorbed by DNA
What is the primary mechanism of UV damage
Formation of thymine dimes in DNA
Why did we remove the lids of the plate when exposing to UV light
UV has a low penetration
Why do we cover the plates after exposing them to UV
To block photoreactions - repairs DNA damage when exposed to light
Is acidity or alkalinity more common in nature
Acidity is more common
- develops in oxidising environments (biosphere predominantly aerobic)
