pseudomonas and cystic fibrosis

Question 1

steps required of a bacteria to cause a disease

Answer 1

• encounter and enter a host
• establich an infectious niche
• multiply, cause tissue damage
• spread to other tissues, or other hosts, or both

Question 2

factors responsible for pathogenicity

Answer 2

• colonization factor
• survival factor
• factors that cause damage or spread
• regulatory factors

Question 3

gram negative

Answer 3

• thin PG layer
• outer membrane
• lipopolysaccharide adhered to the outer leaflet of outer membrane
• periplasmic space between inner and outer membrane which contains a PG layer, lydrolytic enzymes, chemoreceptors, and transport proteins

Question 4

gram postitive envelope

Answer 4

• thick PG
• lipoteichoic acid extending from cytoplasmic membrane outer leaflet
• teichoic acid extending from PG

Question 5

outer membrane

Answer 5

• found on G- bacteria
• phospholipid inner leaflet is a barrier to hydrophilic compounds
• lipopolysaccharide in outer leaflet is negatively charged and resistant to detergents and other hydrophobic molecules
• {PRES in the outer membrane allow entry of small nutrient molecules through outer membrane

Question 6

pores of outer membrane

Answer 6

• allow small hydrophilic compounds to enter the periplasm

- larger moleculse, eg many antibiotics, are too large to enter

Question 7

LPS

Answer 7

• endotoxin
• very potent antigen that causes a strong adaptive immune response
• causes a strong innate immune response with cytokine production and septic shock

Question 8

flagellum

Answer 8

• most common agent of motility
• can be polar or all over the cell (peritrichous)
• attached to a rotary motor protein

Question 9

motility

Answer 9

-allows bacteria to penetrate mucous layers

Question 10

chemotaxis

Answer 10

• movement towards food or away from poisons
• specfici receptors on bacterial cell surface direct motility
• triggered by a signal sensing two component regulatory system

Question 11

regulation of chemotaxis

Answer 11

• sensory histidine kinase
• when molecule comes into contact with kinase, it phosphorylates a response regulator, activating it
• active response regulator causes flagellar rotation

Question 12

adhesins

• where
• what do they do
• specificity

Answer 12

• found on microbial cell surface
• binds to sugars or proteins on the host cell surface
• can be ver specific, some bind to only one type of epithelial cell in one speicies
• some are even specific to very small areas of the mouth

Question 13

potentially adhesive structures of bacteria, where you would find adhesins

Answer 13

• pili (fimbriae)
• flagella
• capsules

Question 14

pili (fimbriae)

Answer 14

• for attachment

- for conjugation, transfer of genetic material

Question 15

capsule

• composition
• function

Answer 15

• loose network of polymers surrounding cell
• polysaccharide or protein or both
• hyaluronic acid (streptococcus)
• sialic acid (neisseria)
• adherence, protection against phagocytosis, protection against environmental stresses

Question 16

examples of extracellular polysaccharide found on p aeruginosa

Answer 16

• alginate

- mucoidy

Question 17

important encapsulated pathogens

Answer 17

• strep pneumoniae
• haemophilus influenza
• neisseria meningitidis
• pseudomonas aeruginosa

Question 18

what are encapsulated bacteria typyically able to cause

Answer 18

• septicemia

- meningitis

Question 19

role of alginate production (mucoidy) in p aeruginosa

Answer 19

• alginte is a polysaccharide excreted by the bact
• greatly thickens the sputum of Cf patients
• coats the bacterial cell forming a capsule-like structure
• protects against host defenses and antibiotics

Question 20

what sigma factor does alginate depend on?

Answer 20

AlgU

Question 21

regulation of AlgU

Answer 21

• held in a inactive state by MucA, a protein that resides in the periplasm which chemically holds AlgU to the inner leaflet of the inner membrane
• when cells sense a cell wall stress, MucA is degraded by a protease in the periplasm, this frees AlgU from the membrane, allowing it to bind to RNA pol and direct transcription of alginate genes

Question 22

why is there so much alginate in the lungs of Cf patients

Answer 22

-they accumuate mutants strains of P aeruginosa that produce a truncated, inactive MucA, leaving AlgU active

Question 23

biofilm formation in nature

Answer 23

1. attachment (Fla+, Pil+)
2. stable binding, growth (Fla-, Pil-)
   3-4. Capsules synthesis (Alg+)
3. Readying for release (Fla+. Pil+)
   6.release of planktonic bacteria

Question 24

signalling compounds of gram neg and gram pos

Answer 24

• gram neg: acylated homoserine lactones

- gram pos: peptides

Question 25

intracellular signalling

Answer 25

• associated with population crowding
• within a species of across species
• within population of dispersed cells or communities

Question 26

production of homoserine lactone quorum sensing molecules

Answer 26

• can be made from aspartate or fatty acids
• aspartate to homoserine to methionine to s-adenosyl methionine to acylated homoserine lactone
• homo serine lactone is used for species specific signalling

Question 27

signal transduction system that responds to intracellular signaling

Answer 27

1. inducer exported
2. environmental factors alter the inducer
3. altered inducer is sensed
4. transmitter is phosphorylated
5. response regulator is phosphorylated
6. phosphoryalted response regulator causes gene activation