bacteria needs to survive stresses like cold shocks .there are mechanisms which able them to adopt to these conditions.one of prominent mechanism is using csp family of proteins

1. Molecular Mechanisms
Of Cold Adaptation
In Bacteria
Presented by:
Afagh Bapirzadeh
Molecular genetics doctorate
student
Under supervisering of:
Dr.Rafieai

2. Normal Cell Culture Growth Vs. Cold Shock Bacterial Growth

3. High temperature versus cold temperature

4. Molecular Mechanisms In Which Bacteria
Use To Adapt Low Temperatures
Altering the fluidity of membrane
Maintaining the stability of DNA
& transcriptional machinery
Unique ability to maintain
enzymatic reactions

5. Membrane Fluidity
• Why we need membrane of bacterial cells to become fluid-like ?
Because low temperature enhance rigidity of membrane .
To maintain membrane function in low temperature such as transport, energy
production ,signal transduction ,cell growth and cell division.
• How can we alter a rigid membrane to a fluid-like one?
Changing the polar
head groups of
glycerophospholipids
Changing the
magnitude of fatty
acid desaturation
Changing the chain
length of fatty acids
Changing the ratio of
iso and anteiso fatty
acids
Changing the
proportion of cis
and trans fatty acids
Presenting a
component of
phospholipids
(EPA)

6. Adaptation Of The Cell Membrane

7. Rapid Desaturation Of Fatty Acids In Already Existing
Phospholipids Of Bacterial Cell Membrane
• Fatty acids unsaturated fatty acids
fatty acid desaturases(Des)
Activates Synthesis
Of D5-desaturase
des gene activation
Binding To Des Gene
Promoter
phosphorylated DesR(transcriptional activator)
Phosphorylation
DesK kinase

8. Adaptation Of RNA Metabolism

9. Cold-shock Proteins
• They were first discovered in 1987
• A family of mostly acidic proteins and small (7.4kDa)
• They existed from beginning of bacterial evolution
• In eukaryotes they have similar sequences in a domain called cold-shock domain
• This domain mediates specific RNA-binding in combination with additional RNA-binding
domains.
• A conserved all beta-strand fold that contains a defined ssDNA/RNA binding epitope.
• Acts as RNA chaperons in bacteria
• They autoregulate themselves.

10. Cold-shock proteins function

11. Transcription Changes During Cold-shock State
The curvature of
DNA changes
• Become more negatively
supercoiled
• This trigger the
transcription of cold-
induced genes
DNA relaxation
increase
• This induces the
expression of a specific
set of genes
CspA & CspE act
as antiterminators
• Functionally linked to
the maintenance of
chromosome structure
• Prevent hairpin
formation that may lad
to premature
termination

12. Degradation And Stabilization
Csps Family
• Capable of binding to DNA
• Functionally linked to the chromosome structure
• CspE can promote or protect chromosome folding
• CspA destabilizes secondary structures and functions as a chaperone to
maintain RNA in a single-stranded state which favours its degradation
Dead-box Helicase
• It is a helicase which incorporate to degradosome ,main RNA degrading
machine
• Helps to degrade structure RNAs
• Also is involved in ribosome biogenesis
• Leads to depletion of the mature 50S ribosomal subunit and
accumulation of the 40S-like particle
PNPase
• One of the main exonuclease of E.coli
• Helps to repress the production of the Csp family of proteins at the end
of acclimation phase.
• With the help of two other exonucleases processively digest RNA
secondary structure

14. Translation Changes During Cold-shock State
PY protein
block
translation
Structural
RNA slow
down
translation
IF2, Hsc66
& TF
correct
protein
folding
Ribosome
adaptation
to cold