Lecture 27

Question 1

What is the cell wall of bacteria made of

Answer 1

Pepitdoglycan

• the rigid macromolecular layer provides strength to cell
• Protect cells from osmotic lysis and confers cell shape

Question 2

What is the structure of the cell wall

Answer 2

NAG-NAG-NAG strands
peptide side-chain amino acid
cross-bridge amino acid
trans peptide strands linked together

Question 3

What is a transpeptidase

Answer 3

the enzyme that cross-links the peptidoglycan chain to form a rigid cell wall

Question 4

What is Gram Stain

Answer 4

common stain technique

Question 5

What happens to gram-positive bacteria

Answer 5

stains purple due to the thick peptidoglycan wall

that traps crystal violet stain

Question 6

What happens to gram-negative bacteria

Answer 6

stains pink due to counterstain

thin peptidoglycan layer with inner and outer (polysaccharides) membranes does not trap violet stain

Question 7

What are the flagella

Answer 7

in motile bacteria

produces movement in a liquid medium

Question 8

What are the 3 sections of the flagella

Answer 8

long filaments - extend into surrounding medium
Hook - curved section connecting filament to cell surface
basal body - anchors the flagellum into cell membrane of the bacterium by special disc-shaped structures called plates or rings

Question 9

What is Chemotaxis

Answer 9

bacteria move along a concentration gradient towards a chemical attraction (positive)
or away from a chemical repellent (negative)
temporal gradient over time

Question 10

What are bacterial adherence factors

Answer 10

fimbriae

structures with adhesive properties to stick some bacteria to surfaces

Question 11

What is glycocalyx

Answer 11

gelatinous polysaccharide and polypeptide outer covering

forms a sticky meshwork of fibres

Question 12

What is a capsule

Answer 12

glycocalyx organised into a defined structure attached firmly to a cell wall

Question 13

What is disorganised glycocalyx without cell shape called

Answer 13

slime layer

Question 14

What are the capsule functions

Answer 14

virulence factors - protecting bacteria from phagocytosis and engulfment by immune cells
adherence to cell surfaces and structures
prevent a cell from drying out

Question 15

What are bacterial endospores

Answer 15

formed during unfavourable growth conditions and germinate under favourable conditions

• protect cells from stress
• only in some gram-positive bacteria - genus bacillus