Micro-L15-Cellular Adhesion- UPEC

what is the role of adhesins in bacterial surface? how is the expression shown?

• adhesins are proteins that confer attachment to surfaces or host cells

• can be always expressed or induced in response to surface sensing

discuss filamentous adhesins: what they are, and examples- what bacteria are these present in

filamentous- gram pos attached to peptidoglycan

• long, thin appendages contacting host receptors

• chaperone usher pili: E.coli, Salmonella

• Type IV pilli- gram 4 pos, retraction, surface contact and DNA transfer

• T4SS conjugative pill: DNA uptake from other bacteria

• flagella: interact with TLRs

discuss non filamentous adhesins: what they are, and examples- what bacteria are these present in

• large surface proteins

• EHEC- attaches to intestinal epithelial cells

• Siie in Salmonella- largest adhesin

• staphylococcus- FnBPA- for clumping

• gram positive- extends past peptidoglycan

• gram negative- extend beyond LPS

what are barriers to bacterial adhesion?

• epithelium/spidermis

• mucus layer- trap bacteria

• physical forces- in the cilia, coughing, sneezing

• secretion- stomach acid, AMPs, IgA

• microbiota- comp for space and receptors

what is UPEC? how it related to E.coli? describe genetics, where it resides, infection type, what kind of bacteria and diagnosis

• not different fromE.coli in the gut but carries type I fimbriae

• lives in the gut normally and synthesises vitamin K

• in disease: colonises and disease in the urinary tract

• gram negative!!!!

• diagnosed by dipstick test which tests nitrides from bacteria, blood in urine, pH changes

what are the virulence factors of UPEC? 5 factors

• chaperone usher pili

• capsule

• toxins- hemolysins

• motility and chemotaxis

• siderophores for iron acquisition

how does UPEC initiate infection in the urinary tract?

• because the urethra is close to the rectum- it can cause colonisation

• type I pili attach to the receptors on bladder epithelial cells
  - targets umbrella cells on surface cells of the bladder and shed during infection

• transitional cells- under the umbrella cells and replenish it

• mechanism: adhesion by type I pili and then destroys epithelial cells. colonises and invades tissues

structure of UPEC pili, what type is it? and what is the assembly process?

• type I chaperone usher pili

• assembly:

1. chaperone FimC delivers plus subunits to the surface

2. usher FimD- mediates export to the cell surface

3. tip adhesin- FimH binds host receptor

• first subunit exported is FimFGH and then 1000 copies of FimA

describe the donor strand complementation in UPEC pili assembly? why’s it needed? and the mechanism

• pilus subunits have an incomplete immunoglobulin folds and are unstable

• incoming strand complement folds and stabilises subunit

• protease DegP degrades misfiled pilins

• chaperones FimC stabilise subunits

how does UPEC interact with host glycans? in urinary tract and kidneys, and innate barriers

• type I fimbriae- bind branched mannose sugars on the epithelial cells

• kidney attachment- secondary pili Pap binds Gb3

• innate barriers: GAGs glycosaminoglycans - mucin like structures

describe the UPEC cellular lifestyle? how it invades, and what it induces.

• once bacteria have attached to umbrella cells- they’re taken up by endocytosis

• bacteria then invades and replicates and make a community callused IBC which is biofilm like and make complex structure

• induce neutrophils by TLR4/TLR5 and get IL6, IL8 and caspases

what form of adhesion do UPEC display? diff between low and strong forces

catch-bond- more stronger under force!

• multiple piles mean stronger attachment under shear stress of urine flow

• fimH(tip) ahdesin has 2 domains and FimG stavilises it

• at low force: FisH binds mannose weakly and can detach easily. when urine flow is strong, it pulls on the pills and separates lectin and pillion and clamps down on mannose

• shear forces separates these 2 domains and increases affinity for the receptor

describe the cost vs benefits(4 and 3) of adhesins

benefits:

• attachment from adhesins are critical for early stage

• some adhesins are specific and allows it to target particular receptors- FimH binding mannose

• can form biofilms and make a community- intracellular bacteria community in UPEC

• can sense mechanosensing

costs:

• immunogenicity and can be recognised by host immune system by TLR4/5 and trigger Ab and complement

• producing long filaments is metabolically expensive and needs energy and resources

• expressing ahdesins in incorrect location can be detrimental and attract immune attention. expression is regulated by environment cues