Adhesion structures Flashcards
What is adhesion?
Attachment to a surface
Why would cells want to attach to something?
Stops them from being flushed out of a particular location, or if a pathogen needs to stay near its host cells, biofilm formation, cell-cell attachments
What is an adhesin?
A cell surface component that assists in attachment to a surface
What are adhesins made of?
Sugars or proteins
What is the structure of protein adhesins?
Filaments made of 1-2 polymerized proteins that extend out from the cell. They’re anchored in the cell wall and membrane with the basal body made of a bunch of proteins
Which part of a protein adhesin is adhesive?
The tip
What are fimbriae?
Short, hollow protein filaments that cover the cell
Are fimbriae specific or non-specific?
Specific
How do fimbriae allow tight interaction between the cell and the surface?
The cell can attach with all their fimbriae at once and create a really tight interaction
What are pili?
Long protein filaments that stretch several cell-lengths away. Cells only usually have a few per cell
What are 2 types of pili?
Sex pili and type IV pili
Why can only some cells produce sex pili?
It requires the F plasmid to make, since it contains the gene for the pilus
What is the sex pilus used for?
For bringing two cells close together to allow horizontal gene transfer and exchange of genetic info
Does the sex pilus carry the DNA from cell to cell?
No, it brings the cells close together to allow the cells to fuse, and the DNA is exchanged at the fusion site
What are type IV pili used for?
Adhesion of pathogens to host cells and twitching motility
What is twitching motility?
When type IV pili extend out of the cell, retract, and pull the cell along a surface in a jerky movement that requires ATP
What are hami?
The archaeal version of pili
Are hami specific or non-specific?
Non-specific
What is the structure of hami?
Protein filament with a barbed hook on the end
How do hami work?
They act like grappling hooks and grab on to impurities in the soil and rocks so they don’t get washed away, as well as to each other to form biofilms
What are capsules and slime layers?
Polysaccharide adhesins found outside the cell
What are capsules?
Tightly organized and cross linked polysaccharide matrix that is tightly attached to the cell
What do capsules do?
Assist in immune system evasion, exclude large molecules from getting into the cell, protect from desiccation
What are slime layers?
Looser and more easily deformed polysaccharide layer around the cell
How tightly are slime layers associated with the cell?
Not very much. They are loose a don’t exclude particles, and tend to be lost quite easily
What are 3 functions of capsules and slime layers?
- Attachment to solid surfaces
- Protection from phagocytosis by immune cells
- Protection from desiccation
Are capsules and slime layers specific or non-specific adhesins?
Non-specific
What are 3 other adhesive structures that aren’t adhesins?
LPS, S-layers, protein holdfasts in appendaged bacteria
How do protein holdfasts in Caulobacter species work?
Extremely tight non-specific association with polysaccharides. They stick so tight that they never move again once stuck to a surface
