LECTURE 7

Question 1

what solidifies the gram positive cell wall?

Answer 1

teichoic acid
(glycerol or ribitol polymers) that runs perpendicular to the peptidoglycan chains
this solidifies the structure

Question 2

how is the gram negative cell wall anchored to the outer membrane

Answer 2

anchored by lipoproteins

Question 3

how is the cell wall anchored to the cytoplasmic membrane in the gram positive cells?

Answer 3

by lipoteichoic acid

Question 4

what are the functions of the outer membrane in gram negative?

Answer 4

protective barrier
only water small molecules and gases can go through
other molecules need to travel through pores (porins)

Question 5

what are the layers of the gram negative outer membrane

Answer 5

phospholipid bilayer
inner layer is phospholipids
outer layer is made of lipopolysaccharides and some phospholipids

Question 6

how do lipoproteins anchor the outer membrane to the cell wall?

Answer 6

protein part linked to the cell wall (peptidoglycan)
lipid part inserted in the inner layer of the outer membrane

Question 7

what is the structure of a lipopolysaccharide (LPS)

Answer 7

Question 8

what characteristics of the capsule/slime layer/s-layer?

Answer 8

1. secreted outside the cell envelope
2. protection from phagocytes and protozoa
3. protection from desiccation, toxic compounds, ions, pH fluctuations and destructive enzymes
4. reservoir of stored food
5. site for waste disposal
6. helps maintain shape and rigidity
7. prevents infection by bacteriophages or attack by predacious bacteria
8. aid in cell adhesion and motility

Question 9

what are characteristics of the capsule?

Answer 9

polysaccharides
thick and well organized
not easy to remove
see well by microscopy

Question 10

what are characteristics of the slime layer?

Answer 10

polysaccharides, glycoproteins, glycolipids
thin and less organised
easy to remove
not easy to see by microscopy

Question 11

what are characteristics of the surface (s) layer

Answer 11

proteins, glycoproteins
highly organised, not easy to remove
see well by microscropy

Question 12

what are the different surface appendages of bacteria?

Answer 12

flagella and pili/fimbriae

Question 13

what are the characteristics of flagella?

Answer 13

used for movement of bacterial cells (rotate, helical)
vary in numbers and arrangement
made of a protein polymer flagellin

Question 14

what are characteristics of pili/fimbriae?

Answer 14

hairlike, thinner than flagella
1000 per cell
provide adherence to solid surfaces

Question 15

what are sex pili?

Answer 15

for mating
larger than fimbriae (1-10 per cell)
genetically determined by sex factors or conjugative plasmids

Question 16

how are bacterial flagella organised in gram positive vs negative?

Answer 16

Question 17

what are typical arrangements of flagella?

Answer 17

monotrichous: single flagellum at one pole

amphitrichous: single flagellum at each pole

lophotrichous: two or more flagella at one or both poles

peritrichous: flagella all over the surface

Question 18

what is bacterial movement called?

Answer 18

taxis

Question 19

how to monotrichous bacteria move?

Answer 19

counterclockwise; cell goes forward
clockwise: cell tumbles

Question 20

how do peritrichous bacteria move?

Answer 20

counterclockwise flagella form a single rope like structure and the cell goes forward
clockwise, the cell tumbles

Question 21

what are the different bacterial movements (taxes)?

Answer 21

chemotaxis; towards/away from a specific chemical agent

aerotaxis: towards/away from regions rich in oxygen

phototaxis: towards light

magnetotaxis: follow magnetic lines of force

Question 22

how does chemotaxis work?

Answer 22

towards nutrients or pheromones
away from detergents
movement is directional
runs are longer than tumbles, the movement is not completely random