pseudomonas and cystic fibrosis Flashcards
steps required of a bacteria to cause a disease
- encounter and enter a host
- establich an infectious niche
- multiply, cause tissue damage
- spread to other tissues, or other hosts, or both
factors responsible for pathogenicity
- colonization factor
- survival factor
- factors that cause damage or spread
- regulatory factors
gram negative
- 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
gram postitive envelope
- thick PG
- lipoteichoic acid extending from cytoplasmic membrane outer leaflet
- teichoic acid extending from PG
outer membrane
- 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
pores of outer membrane
- allow small hydrophilic compounds to enter the periplasm
- larger moleculse, eg many antibiotics, are too large to enter
LPS
- endotoxin
- very potent antigen that causes a strong adaptive immune response
- causes a strong innate immune response with cytokine production and septic shock
flagellum
- most common agent of motility
- can be polar or all over the cell (peritrichous)
- attached to a rotary motor protein
motility
-allows bacteria to penetrate mucous layers
chemotaxis
- movement towards food or away from poisons
- specfici receptors on bacterial cell surface direct motility
- triggered by a signal sensing two component regulatory system
regulation of chemotaxis
- sensory histidine kinase
- when molecule comes into contact with kinase, it phosphorylates a response regulator, activating it
- active response regulator causes flagellar rotation
adhesins
- where
- what do they do
- specificity
- 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
potentially adhesive structures of bacteria, where you would find adhesins
- pili (fimbriae)
- flagella
- capsules
pili (fimbriae)
- for attachment
- for conjugation, transfer of genetic material
capsule
- composition
- function
- 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
examples of extracellular polysaccharide found on p aeruginosa
- alginate
- mucoidy
important encapsulated pathogens
- strep pneumoniae
- haemophilus influenza
- neisseria meningitidis
- pseudomonas aeruginosa
what are encapsulated bacteria typyically able to cause
- septicemia
- meningitis
role of alginate production (mucoidy) in p aeruginosa
- 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
what sigma factor does alginate depend on?
AlgU
regulation of AlgU
- 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
why is there so much alginate in the lungs of Cf patients
-they accumuate mutants strains of P aeruginosa that produce a truncated, inactive MucA, leaving AlgU active
biofilm formation in nature
- attachment (Fla+, Pil+)
- stable binding, growth (Fla-, Pil-)
3-4. Capsules synthesis (Alg+) - Readying for release (Fla+. Pil+)
6.release of planktonic bacteria
signalling compounds of gram neg and gram pos
- gram neg: acylated homoserine lactones
- gram pos: peptides
intracellular signalling
- associated with population crowding
- within a species of across species
- within population of dispersed cells or communities
production of homoserine lactone quorum sensing molecules
- 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
signal transduction system that responds to intracellular signaling
- inducer exported
- environmental factors alter the inducer
- altered inducer is sensed
- transmitter is phosphorylated
- response regulator is phosphorylated
- phosphoryalted response regulator causes gene activation
