Introduction following to a journal in order to show properties of curli, one of the functional amyloid in nature! This is the best approach for people who were interested in curli.

1. Curli Biogenesis and Function
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2. 2
Definition of Curli
Curli biogenesis
Role of curli
Conclusion

3. 3
Definition of Curli
Curli
The major proteinaceous component of complex
extracellular matrix produced by Enterobacteriaceae,
involved in adhesion to surfaces, cell aggregation, and
biofilm formation.
A part of a growing number functional amyloid with
biochemical and structural properties as eukaryotic amyloid
fibers. (nonbraching and β-sheet rich fibers)

4. 4
Presence of Curli in Salmonella typhimurium grown on CR-indicator plates
for 48h at 26oC.
• Rdar : red, dry and rough
• Pdar : pink, dry and rough
• Bdar : brown, dry and rough
• Saw : smooth and white

5. 5
(a & b) bacterium expressing
and non-expressing curli strains
(c) High-resolution Electron
Micrographs of purified CsgA
fibers.

6. 6
Curli biogenesis
Operon Composition Function of gene
CsgA 30% of
sequence
identify
Major structural subunit
CsgB Nucleator protein
CsgD Center of the curli regulatory network
CsgG Required for stability and secretion of CsgA, CsgB
CsgE, CsgF
Interact with CsgG, required for efficient curli
assembly
- Genes impotant
for curli formation
in E. Coli.

7. 7
A model of the predicted strand-loop-strand motif of CsgA
A similar prediction was made for CsgB

8. 8
Role of curli
Adherent
ability
Biofilm
formation
pathogenesis
Attatchment and
invasion of host cell
- Important for biofilm development in
both E. Coli and Salmonella.
- Allow a nonadherent strain E. Coli to
form biofilms.
- Effect to morphology of biofilm.
- Important during the infectious
process.
- Interaction with host protein and
activation of immune system.
- Facilitate bacterial dissemination
through the host.
- Curli expressing strain adhere to
various eukaryotic cells better than
noncurliated strains do.
- Promote binding to plant cells.
- Play some role in reason causing
Sudden Infant Death Syndrome (SIDS).

9. 9
Adherent
ability
Of
Curli
- Curli allow Salmonella enteriditis to adhere to Teflon and
strainless steel lead to biofilm formation and contamination of
material surfaces.
- During biofilm formation, E. Coli K-12 is able to produce curli at
37oC, though on agar plates or in static broth it is able to express
curli at only 26oC.
- Curli bind to plasminogen and t-PA simultaneously => activate
plasminogen to plasmin, this enzyme degrades soft tissue, which
allow bacteria to access to deeper tissue.
- Invasion by K-12 isolates expressing curli can be inhibited by
peptides that block curli formation.
- Salmonella enterica a deletion of csgB decreased adherence to
alfalfa sprouts.

10. 10
Conclusion
Curli represent a fascinating system to study many aspects
• Understanding the complex macromolecular interactions
promote amyloid formation.
• Studying protein secretion and macromolecular assembly in
gram-negative bacteria.
• Understanding the complex interplay among multiple
regulatory pathways. (curli are tightly regulated)
• Key role in mediating biofilm formation.
• Ability to promote adherence to multiple cell lines.

11. THANKS
FOR YOUR ATTENTION.
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