Fimbriae
short and many; help bacteria stick to surfaces, like how Velcro grips.(made of protiens)
Pili
longer and fewer; used to transfer DNA between cells (like a tiny bridge) or attach to other cells.(made of protein)
Pseudomonas aeruginosa
A Gram-negative, rod-shaped bacterium that needs oxygen and doesn’t form spores.
Has Type IV pili, which help it move (twitching motility) and stick to surfaces — the first step in infection.
It’s an opportunistic pathogen, meaning it mainly infects people with weak immune systems.
Common in hospital-acquired infections (HAIs).
Hard to treat because it’s very adaptable, resistant to many antibiotics, and has strong defense systems.
Twitching motility of type iv pili
It allows them to attach to epithelial cells (cells that line tissues and organs).
Once attached, this triggers gene expression related to biofilm formation and pathogenicity (how harmful the bacteria can be).
bacteriophage
A bacteriophage is a virus that infects and replicates only in bacterial cells, making it a naturally occurring “bacteria-eater”.
how many types of pili are there for gram negative
five major classes based on their biosynthetic pathway
Chaperone-Usher Pili
-Chaperone-Usher Pili are special hair-like structures found on Gram-negative bacteria that help them infect and stick to host cells.
-The chaperone helps build the pili correctly inside the cell.
-The usher helps move the pili to the surface.
-These pili are important for starting and maintaining infections because they let bacteria stay attached, even in harsh conditions.
-They also help bacteria form biofilms, which make them harder to remove or kill.
Important virulence factors” just means
tools or features that make a bacterium able to cause disease.
Type IV Pili
-They are important for virulence
-They have variable and conserved regions, which means some parts change and stay same
Antigenicity
Antigenicity is a term that describes how easily a substance (like a protein on a bacteria) is recognized by the immune system.
If something has high antigenicity, your immune system can detect it quickly and make antibodies against it.
If something has low antigenicity, it’s harder for the immune system to notice, so the bacteria can hide better.
SUBTYPE of Type IV Pili in E. coli include a special kind called Bundle Forming Pili (Bfp).
Essential for full virulence → without Bfp, E. coli can’t cause disease properly.
Adherence → helps the bacteria stick to epithelial cells (cells lining the gut).
Auto-aggregation → helps bacteria stick to each other, forming clusters or microcolonies.
So basically: Bfp are “sticky hairs” that let E. coli attach to surfaces and form colonies, which is necessary for infection.
Curli
Curli are coiled, hair-like structures on the surface of some bacteria.
They bundle together to form structures called aggregative fimbriae.
Their main job is to help bacteria stick to surfaces or host cells.
They also help form biofilms, which are protective layers that make bacteria harder to remove or kill.
Pili (fimbriae) what it do
Adherence, aggregation, invasion, virulence, biofilm initiation and development, motility, Dna uptake (conjugation), motility and signaling, chemotaxis and phototaxis,
pili classification
Bacteria pili can be grouped based on different features:
Major pilin subunit – the main protein that makes up the pilus (e.g., Bfp in E. coli).
Adhesin – whether the pili are specialized for sticking to surfaces or host cells.
Assembly mode – how the pilus is built and brought to the cell surface (e.g., chaperone–usher pili vs. Type IV pili).
Motility/Retraction – whether the pili can pull the bacterium along a surface (like Type IV pili that enable twitching motility).
Classification of Pili: Adhesin
adhesive is the stick part on the pili which binds to cells, Different adhesins recognize different molecules on the host cell surface ex. carbohydrates, glycoproteins, glycolipids on host cell
Classification of Pili: Assembly Mechanisms
Chaperone-Usher Pathway (CUP):
Example: Type I pili in E. coli
How it works: Small helper proteins called chaperones stabilize pilus subunits in the periplasm (space between membranes) and deliver them to an usher protein in the outer membrane that assembles the pilus fiber and pushes it out of the cell.
Nucleation/Precipitation Pathway:
Example: Curli fimbriae in E. coli
How it works: Pilus subunits are secreted and assemble outside the cell in a self-organizing way. Curli are amyloid-like fibers used for biofilm formation.
Type IV Pilus Pathway:
Example: Bundle-forming pilus (BFP) in E. coli
How it works: These pili are built by a complex system that uses an ATP-powered motor to push and retract the pilus, allowing bacteria to “twitch” and move along surfaces.
PilQ
a gated multimeric outer
membrane pore protein through
which the growing pilus is
assembled and disassembled
ATPases PilB, PilT:
responsible for pilus elongation and retraction –
rotate PilC
MV140 vaccine
Made from whole bacterial cells that are heat-killed (so they can’t cause disease). to train ur immune system
Contains a mixture of four bacteria that commonly cause infections:
Escherichia coli – gut bacterium, can cause UTIs.
Klebsiella pneumoniae – can cause pneumonia and UTIs.
Enterococcus faecalis – gut bacterium, can cause UTIs and bloodstream infections.
Proteus vulgaris – often linked to urinary tract infections.
Equal percentages of each strain are included so the immune system can learn to recognize all four.
