microbiology

Question 1

what characteristics effect bacterial growth

Answer 1

speed, morphology, atmosphere, temperature

Question 2

what does the cell envelope provide

Answer 2

protection from osmotic lysis
protection from host defences
shape and rigidity
semi-permeable membrane

Question 3

Gram-positive peptidoglycan features

Answer 3

• Has 2 sugar derivatives connected by β1-4 links:
  o N-acetyl glucosamine
  o N-acetyl muramic acid
• Form a repeating structure called glycan tetrapeptide
• Glycan chains connected by peptide cross links of 44 amino acids to provide rigidity
• Cross links of NAM with a tetrapeptide
• In Gram positive cross links involve peptide interbridge

Question 4

Gram negative cell wall

Answer 4

• thinner but more complex
• cytoplasmic membrane + thin peptidoglycan layer
• in periplasmic space between CM and inner surface of outer membrane
• periplasmic space contains variety of hydrolytic enzymes required to break down large macromolecules for metabolism

Question 5

gram negative periplasmic space

Answer 5

• Enzymes include protease, phosphates, lipases, nucleases and carbohydrate degrading enzymes
• Sugar transport systems and binding proteins
• Components of chemotaxis system, sensing environment outside the cell
• In pathogenic bacteria, will be virulence factors such as collagenases, hyaluronidases, proteases and beta-lactamase

Question 6

what are flagella?

Answer 6

• Long thin appendges originate from cytoplasmic membrane
• Extend through the cell wall into surrounding membrane
• Enable bacteria to be mobile (motility)
• Very thin (20nm)
• Not visible by light microscope unless stained

Question 7

what are the three flagellar components?

Answer 7

The motor
Hook
Filament

Question 8

what is the motor known as?

Answer 8

the basal body

Question 9

What does the hook do?

Answer 9

has a single class of proteins at flagellum base of the flagellum connecting filament to motor

Question 10

What are endospores resistant to?

Answer 10

Drying
Heat
Pressure
Many chemical disinfectants

Question 11

How are formation of spores stimulated by environmental conditions?

Answer 11

lack of nutrients
temperature change
redox potential

Question 12

3 stages of formation of spores?

Answer 12

activation
germination
outgrowth

Question 13

how is activation done in spores

Answer 13

by heating at sub-lethal but elevated temperature

Question 14

how are spores germinated?

Answer 14

when placed in nutrients
loss of resistance to heat and chemicals
loss of Ca dipicolinate and cortex components
acid-soluble spore proteins degraded

germination converts back to vegetative cell relatively rapid

Question 15

outgrowth phase of endospores

Answer 15

visible swelling of - water uptake and synthesis of new RNA, proteins, DNA
cell emerges from broken spore and begins to divide