7 - Pili/Fimbriae And Endospores Flashcards
1
Q
Types of pili/fimbriae
A
- Type 1
- P-pili
- Type 4 Pili
2
Q
Type 1 Fimbriae info
A
- well characterised fimbrial system
- widespread in enterobacteria, most E. coli
- important virulence factor in a range of pathogens
- thin, 7nm wide, and approx. 1-2 micrometers long surface polymer
- bul of fimbriae made of 500-3000 subunits of the protein - FimA - stacked in a helical cyclinder
3
Q
Type 1 fimbriae structure
A
4
Q
P-pili info (P-fimbriae)
A
5
Q
Type 4 pili info
A
- widely distributed in gram negatives
- few examples in gram positives (Clostridia)
- typically longer than fimbriae (up to 10 micrometers)
- only few pili per cell (only 1-10)
- typically pili at both cell poles
- most pili are not hollow unlike flagella
- twitching mobility
6
Q
Type 4 pili structure
A
- Thin (6-8nm wide), flexible fibres, several micrometers long
- fibres often aggregate laterally to form bundles
- bundling mutants lack virulence
7
Q
Type 4 pili functions
A
- host cell adhesion
- biofilm formation (EPEC)
- twitching motility, crawl along a surface
- enable enteropathogenic E. coli (EPEC) to form microcolonies on tissue monolayers
8
Q
Species specificity of pathogens
A
- many pathogens are species specific
- …
9
Q
E. Coli adherence
A
10
Q
Where toxic and non-toxic strains of E. Coli attack
A
Toxic -
Non-toxic -
11
Q
F pilus info
A
12
Q
Sex pilus info
A
13
Q
Conjugation info
A
14
Q
Bacterial endospores info
A
- dormant stage in bacterial life cycle
- called endospores as they form inside bacterial cell
- very different from fungal expospores
- survival stage
- extremely resistant to heat
- some viable for 100,000 years
- dispersal stage through wind, water and faeces
- form when a vegetative cell becomes stressed
- produces a dormant endospore
- May germinate when conditions become favourable again and produce new vegetative cell
- found commonly in soil bacteria
- Genera usually Bacillus, Clostridium, Sporoarcina
- only gram positives produce endospores
- spore formers include important pathogens
15
Q
How endospores travel
A
Wind, water, faeces, etc.
19
Q
Stages of sporulation - mechanism
A
- vegetative cell under stress
- DNA organised along cell axis
- a genome copy enclosed in foreshore septum
- foreshore produced by membrane invagination
- cell membrane engulfs forespore in a second membrane
- cortex between membranes accumulate calcium and dipicolinic acid, becomes dehydrated to <10% water
- resistance to heat and chemical increases
- complex exosporium layers are produced
- spore matures with complex cortical layers
- original cell lysis releasing spores
