Transcript I. Heat denatures proteins

Which of the following is true?
A. One bacterium (one bacterial cell) could move around from
boiling waters to freezing waters to sulphur springs because
it can adapt relatively quickly
B. Bacteria and archaea as a group can inhabit boiling waters,
freezing waters and sulfur springs because they can adapt
relatively quickly
C. Bacteria that live in sulphur springs probably use aerobic
cell respiration just like we do (use O2 as e-acceptor and sugar
as e-donor)
D. A and B
E. All of the above
Bacteria are impressively numerous
Bacteria are impressively diverse
~how they acquire nutrients
~how they utilize nutrients
~allows them to inhabit virtually any niche
~allows them to coexist with other species without
competition
~Scientists exploit their diversity for things like
bioremediation
Amazing Adaptations of Bacteria
Hot Springs (100ºC)
Arctic ocean (~1ºC)
Basics of
Temperature Tolerance
•Each organism has a range of internal temperature tolerance
(temp at which they can survive)
•Some species can survive a broad range of internal temps
and some more narrow
•An organism is adapted to be able to survive the temp of the
environment it lives in.
•For MANY organisms (not us),
internal temp = environmental temp so usually no need to
distinguish between the two
Basics of Temperature Tolerance
Broad Tolerance Range: Plants
•Plants can’t move away from cold or heat
•Unlike us, they can’t thermoregulate
so their inside temp = outside temp
•B/c of that, plants have
adaptations to survive high and low
temps.
Basics of Temperature Tolerance
Narrow Tolerance Range
Animals exposed to only a
narrow external
temperature (like
cave dwellers).
Animals exposed to a broad external temperature range but
have a narrow internal temperature tolerance b/c they can
thermoregulate (like mammals and birds)
Basics of Temperature Tolerance
Ability to tolerate temperature in all
organisms affected by their
surface area to volume ratio
Basics of Temperature Tolerance
Surface area to volume ratio affects temp
tolerance in all organisms
Heat is lost through the surface and stored in the volume
high
So if S/V ratio high, than heat loss is ________
Therefore larger organisms (low S/V ratio) are better
adapted for cold climates and smaller organisms better
in hot climates. Exceptions to this would involve
specific adaptations.
Basics of Temperature Tolerance
SA/V examples
Small lizards: high S/V ratio =>can’t tolerate cold well
• relatively lots of surface to lose heat through and
• relatively little volume to store it
Polar bears: low S/V ratio can tolerate cold
•relatively little surface to lose heat through and
• relatively lots of volume to store it
So what about bacteria?
Can they move away from temp extremes?
NO
Can they thermoregulate?
No, so internal temp=external temp
High SA : Volume ratio so without any
specific adaptations would expect them to
survive only in warm temperatures
BUT, bacteria (and archaea) as a group are well adapted to many
different temperature extremes allowing them to inhabit just about
any niche
Temperature Ranges of
Prokaryotes
Prokaryotes divided into three groups based on range of
temperature tolerance.
Within these groups each species of bacteria has
one optimal temperature
PSYCHROPHILES
< 15OC
DEATH OVER 25OC
MESOPHILES
20OC-50OC
Room temperature = 25OC
THERMOPHILES
50OC-130OC
MESOPHILES 20-50OC
Usually live inside other
organisms, especially mammals
and birds which have a constant
internal temperature
within this range.
Examples: bacteria you have heard of including
human pathogens (E.coli, Staph.,Strep., Salmonella)
PSYCHROPHILES <25OC
Found mostly cold ocean bottoms
THERMOPHILES
50OC to >130OC
Hydrothermal vent 130OC
Hot spring 100OC
Hot water
heater
Compost
Pile 60-65OC
Grand Prismatic Spring in Yellowstone
Sulfur springs … high temp
Brainstorm: Why would extreme temperature
environments be tough for a life form?
What types of adaptations
are necessary
to survive boiling water or
freezing water?
First need to understand, what
high heat or freezing
conditions would do to cells?
How do temp extremes affect
organisms?
1. Heat affects proteins (denatures them)
2. Cold affects reaction rate
3. Heat and cold change the properties of cell
membranes.
4. Heat denatures DNA
Heat denatures proteins: Bad for life.
• 3D shape of protein critical to it’s
function
• Proteins contain many bonds of
varying strength that stabilize the
protein and give the 3D shape
– Peptide bond (C-N)
• Relatively strong
• Link Amino acids
– Ionic
• + and – charged R groups
• Strong
– Hydrogen
• Relatively weak
• b/t H and O of AA.
I. Heat denatures proteins
Which bonds are broken by heat first? Hydrogen (weak)
You might predict that thermophiles have relatively more of which type
of bond? IONIC (strong)
Peptide bond
2. Effects of Cold Temps on Proteins
What effect would you predict that cold temps have on cell reactions?
Slow down cell reactions (enzyme reactions; enzymes are proteins)
Because:
•Enzymes have to physically contact their substrate
•Thermal energy causes the enzymes and substrates to move increasing
chance the two will run into each other.
II. Effects of Cold Temps on Proteins
How do psychrophiles
retain effective enzyme reactions
Example: Enzyme may bind better to substrate.
It may not encounter the substrate as often b/c
of cold temps., but when it does, it will have an
easier time binding.
vs
*Degree to which enzymes fit with substrate
varies. The more efficient reactions involve
a good fit between the two
How do temperature extremes effect cells?
3. Cell Membrane Effects:
What would you predict to be the effect of temperature on
permeability of cell membranes?
In low temps, phospholipids Less mobile, decreasing
permeability relative to what is normal
In high temps, phospholipids more mobile, increasing
permeability relative to what is normal
Because:
Membranes held together by weak interactions broken by heat
energy
How do temperature extremes effect cells?
3. Cell Membrane Effects:
What would you predict to be the structure of the phospholipids
in the cell membrane of psychrophiles relative to mesophiles
or thermophiles?
What would you predict to be the structure of the phospholipids
in cell membrane in thermophiles relative to psychrophiles or
mesophiles?
PSYCHROPHILES
•More unsaturated phospholipds
•Longer tails
Result: remains fluid and semipermeable even when
very cold
Unsaturated
Saturated
Aside from lateral movement of phospholipids,
extreme heat can separate the two layers
Without extreme heat (functional)
With extreme heat (if no adaptations) nonfunctional
Weak bonds break
Basics of Temperature Tolerance
SA/V examples
Small lizards: high S/V ratio =>can’t tolerate cold well
• relatively lots of surface to lose heat through and
• relatively little volume to store it
Polar bears: low S/V ratio can tolerate cold
•relatively little surface to lose heat through and
• relatively lots of volume to store it
Thermophiles:
Adaptations to Cell Membranes
In high heat, higher percentage of saturated phospholipids
In extremely high temperatures, organisms have a lipid
monolayer, not lipid bilayer (fusion of the tails of the bilayer).
Resistant to heat
breaking apart
the two layers
4. Heat denatures DNA
• Many Hydrogen
bonds: susceptible to
heat. (Think PCR).
• Which pairs would be
stronger?
_________________
DNA has weak H-bonds and is therefore
susceptible to heat denaturation
•Some thermophiles have a
higher % of Gs and Cs (compared
to As and Ts)
G and C are triple bonded
A and T are double bonded
•Higher G C content makes
DNA less susceptible to
denaturation by heat
•This doesn’t change the
genetic code, changes
are in non-coding region.
Interesting Applications of
Extremophiles
Industrial use of their enzymes
•food processing,
•baking and brewing,
•paper
•bleaching,
• PCR
•Bioremediation (psychrophiles)
•pharmaceutical industry
Astrobiology: conditions on other planets extreme.
Extremophiles provide clues about what kind of life
could survive there.
Clicker Question
Over the summer you get bored and decide to do an
analysis of some bacteria you find in your parent’s hot
water heater and compare it to some bacteria living
at the base of your parent’s toilet. You should expect to find:
A. Hot water heater bacteria have a higher percentage of
unsaturated fatty acid tails in their phospholipids
than toilet bacteria
B. Hot water heater bacteria have a higher percentage of
hydrogen bonds in their proteins relative to ionic bonds
than toilet bacteria
C. Hot water bacteria have a higher percentage of Gs and Cs
in their non-coding DNA than As and Ts compared to toilet
bacteria