Lecture 3

Question 1

what are bacterial endospores for

Answer 1

provides a metabolic survival state that allows bacteria to survive extreme environments. The bacteria becomes dormant and waits out the harsh conditions until the conditions are favourable again in which the the bacteria can germinate into its active dividing.

• extreme temp, UV raiation, lack of nutrients, etc

Question 2

the formation of an _____ from a ____ takes about 8 hours compared to the other way around which takes 15 minutes

Answer 2

endospore from a cell
(cell —-> endospore)

Question 3

how is an endospore formed

Answer 3

under stress the bacteria undergoes the endospore formation pathway which starts in the same way as binary fission. The cell elongates and forms a septum BUT it divides the cell asymmetrically. the small part of the formation becomes the endospore whilst the bigger/parent part contributes to the formation but degrades once the endospore is fully formed

Question 4

name the 4 structural areas of an endospore and all its components

Answer 4

inner to outer

1. normal cell structures
   core, inner membrane, germ cell wall (dna ribosome)
   - metabolically inactive
2. layered structure
   cortex, outer membrane - less crosslinking
3. coat - surrounds cortex, protein layers, thick, impermeable, responsible to resistance to chem and UV
4. exposporium - lipid coat

Question 5

what determines physical resistance to chem and UV

Answer 5

coat (thick layers)
inner membrane (impermeable

Question 6

what determines chemical resistance to chem and UV

Answer 6

(core)
- low water content (15%, compared to >80% in vegetative cells) - more gel like, immobilises proteins and nucleac acids inactivates
- lower pH
- high content of dipicolinic acid and Ca2+ (makes lattice structure)

(Cortex)
decreased peptidoglycan crosslinking - required for the maintenance of the dehydration in the endospore core, and the accompanying metabolic dormancy and heat resistance

Question 7

endospore germination

Answer 7

spore emerges and developes back into active bacterial cell - binary fission an population growth results again

Question 8

death of microorganisms mean

Answer 8

loss of ability to multiply under any known conditions

Question 9

sterilisation means

Answer 9

complete removal or destruction of all microorganisms from inanimate objects. it is brought about by the use of physical or chemical methods. non-selective

Question 10

why is steam/moist heat important?

Answer 10

pressure raises the boiling point of water so that steam with a higher temperature is produced (pure steam = crucial)

Question 11

examples of moist heat method

Answer 11

autoclave
boiling
pasteurisation

Question 12

dry heat is less effective compared to moist heat because of…

Answer 12

oxidation of vital proteins in bacterial cell
- no water molecules to transfer energy

Question 13

examples of dry heat

Answer 13

flaming/incineration
hot air oven