Download Life at extreme temperatures

SYMPOZJUM DOKTORANCKIE
Life at extreme temperatures
Bartosz Różycki
IF PAN
Warsaw, November 3, 2016
Temperatures on Earth
Extreme temperatures on Earth
World Meteorological
Organization – the lowest and
highest air temperature ever
directly recorded at ground
level
on Earth:
−89.2 °C (Vostok
Station
in Antarctica, July 1983)
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56.7 °C (Death Valley, USA, July 1913)
- geothermally heated water: hot springs (up to 100
°C), deep-see hydrothermal vents (up to ~400 °C)
Life at extreme temperatures
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L.J. Rothschild & R.L. Mancinelli, Nature 409, 2001
Life at extreme temperatures
thermophiles – some like it hot
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L.J. Rothschild & R.L. Mancinelli, Nature 409, 2001
Life at extreme temperatures
psychrophiles/cryophiles – some like it cold
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(Himalayan midge)
Nature 310, 1984
Liquid water on Earth
500
deep-see hydrothermal vents
Temperature [°C]
400
300
200
100
0
Antarctic salt lakes
Don Juan Pond (Antarctica) does not freeze at -50 °C
413 g of CaCl2 and 29 g of NaCl per kg of water
What are the limits of temperature
for life on Earth?
What are the limits of temperature
for life on Earth?
…definition of life…
Merriam-Webster: Living
organisms have the capacity
for metabolism, growth,
reaction to stimuli, and
reproduction
Properties of life
1.
2.
3.
4.
5.
6.
7.
Homeostasis (regulation of the internal
environment to maintain a constant state)
Organization (entities composed of one or
more biological cells)
Metabolism
Growth
Reproduction
Response to stimuli
Adaptation (through natural selection) to
environment in successive generations
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(we live
on a
microbial
planet)
Woese et al., PNAS, 1990
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The three domains of life have arose from a common
ancestor
Bacteria and Archaea are prokaryotic organisms
Eukaryotic organisms evolved from Archaea
The cyanobacteria (ancestors of all oxygen-producing
photosynthetic organisms) are not deeply rooted
Life at extreme temperatures
Eukaryotes
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archaea
bacteria
algae
fungi
protozoa
plants
animals
L.J. Rothschild & R.L. Mancinelli, Nature 409, 2001
What are the limits of temperature for
life on Earth?
Himalayan midge (insect) remains active at -16 °C
Yeast Rhodotorula glutinis can cause frozen food spoilage at -18 °C
Planococcus halocryophilus, a gram-positive bacteria, isolated from high Arctic
permafrost, grows and divides at -15 °C and is metabolically active at -25 °C
Water bears / moss piglets (microanimals) can survive a few days at
-200 °C
What are the limits of temperature for
life on Earth?
Strain 121 (Geogemma barossii,
Archaea), found near a hydrothermal
vent, is able to grow and reproduce at
121 °C, the highest temperature
demonstrated to date (Science 2003)
130 °C is the biostatic for Strain 121:
although growth is halted, the archaeum
remains viable, and can resume
reproducing once it has been transferred
to a cooler medium
Microbial Genome Project Database
Are they loving or just tolerant?
Mesophilic organisms10 °C < T < 45 °C
plant pathogens –
Extremeotolerant organisms Example:
bacteria – found in the
Extremeophilic organisms
stratosphere
Ø
cryophiles live at T < -2 °C
Ø
psychrophiles grow optimally at T < 10 °C
Ø
thermophiles thrive at T > 45 °C
Ø
hyperthermophile live at T > 75 °C
found in various geothermally heated regions such
as hot springs and deep-see hydrothermal vents as
well as decaying plant matter (compost)
found in oceans (which cover 70% of the Earth’s surface), polar regions,
mountains…
Living organisms are sensitive to
temperature changes
Growth rate
extremeophilic
microorganisms
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Temperature (°C)
Negative effects of
high temperature
Examples:
low solubility of O2 and CO2 in water (example: no fish found at T > 40
°C)
degradation of chlorophyll at T > 75 °C (meaning no photosynthesis)
denaturation of proteins and nucleic acids
increased fluidity or damage of cellular membranes
Negative effects of
low temperature
Examples:
increased viscosity of fluids; slower diffusion; smaller mobility of nutrients
and wastes
formation of ice crystals
enzyme kinetics
decreased fluidity of cellular membranes (liquid-gel transition of lipid
membranes)
How have the living organisms adapted
to extreme temperatures?
molecular mass
Molecules of life
Molecular Biology of the Cell (© Garland Science 2008)
Water
NASA
Polarity
Molecular Biology of the Cell (© Garland Science 2008)
Polarity
Polar molecules, such as H2O,
have a permanent dipole
moment
molecule [D]
H2O
1,85
HCl
1,08
CO
0,117
O2
0
1D=3,33564
 10-30 Cm
Molecular Biology of the Cell (© Garland Science 2008)
Are they scared of water?
C-C and C-H bonds are non-polar
Example: hydrocarbons
Oils consists of hydrocarbons
hydrophobic
Hydrogen bonds
Molecular Biology of the Cell (© Garland Science 2008)
Hydrophilic
polar molecules
hydrogen bonds
Molecular Biology of the Cell (© Garland Science 2008)
ions
electrostatic interactions
Hydrophobic
•
Water molecules do not form hydration layers around such molecules
Molecular Biology of the Cell (© Garland Science 2008)
Hydrophobic effect
Hydrophobic molecules tend to
contact one another…
… because of the entropy of water
Molecular Biology of the Cell (© Garland Science 2008)
BioMacroMolecules
Lipids
Nucleic acids (RNA & DNA)
Proteins
BioMacroMolecules
Lipids
Nucleic acids (RNA & DNA)
Proteins
Lipids: it is a matter of heads and tails
lipids are amphipathic molecules
phospholipid
lipid bilayer
Lipid bilayers & cellular membranes
The plasma membrane is a
boundary between the interior of a
living cell and its environment. It
regulates the transfer of materials
and information in and out of the
cell.
Molecular Biology of the Cell (© Garland Science 2008)
Lipid membranes of psychrophiles
Challenge: sustain membrane fluidity at low temperatures (fluid-gel transition)
Lipid membranes of psychrophiles
Challenge: sustain membrane fluidity at low temperatures (fluid-gel transition)
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reduced size of Second level
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the head groups
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increased
(poly)unsaturate
d to saturated
lipid ratios
shorter tails
Unsaturated lipids
Lipid membranes of thermophiles
Challenge: prevent membrane damage at high temperatures
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BioMacroMolecules
Lipids
Nucleic acids (RNA & DNA)
Proteins
Nucleic acids
Molecular Biology of the Cell (© Garland Science 2008)
polynucleotide
Nucleic acids: everyone pair up!
Base pairs
DNA melting - things are unraveling fast
T < Tm
T > Tm
DNA melting - three are better than two
Tm depends on the fraction
of the G:C base pairs, which
have 3 hydrogen bonds
T < Tm
T > Tm
increased G:C fractions
are found in the DNA of
prokaryotic thermophiles
Genetic code
The central dogma of molecular biology
DNA
3 base pairs – codon – one amino acid
transcription
(polymerase)
RNA
translation
(ribosome)
proteins
DNA codon table (Wikipedia)
T < Tm
T > Tm
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melting temperature Tm (°C)
DNA melting - with a pinch of salt
Tm depends on the fraction
of the G:C pairs in the DNA
molecule, and also on the
G:C fraction
salt concentration in the
(Biochemistry 43, 3537-3554, 2004)
solution
Salts enhance the stability of nucleic acids because they
screen the negative charges of the phosphate groups
KCl, MgCl2 … are found at higher levels in thermophilic
archaea
Protein machineries prevent DNA
melting
Reverse DNA gyrases induce positive supercoiling of
DNA, which raises Tm. These proteins appear to be unique
to hyperthermophiles. Their function is to protect the
genome from denaturation.
Wikipedia
Biochemical Society Transactions 31, 58-63, 2011
BioMacroMolecules
Lipids
Nucleic acids (RNA & DNA)
Proteins
Amino acids
Molecular Biology of the Cell (© Garland Science 2008)
amino
group
carboxyl
group
polypeptides
Protein secondary structure:
amino acid sequence
Molecular Biology of the Cell (© Garland Science 2008)
Secondary structure: α helices
Molecular Biology of the Cell (© Garland Science 2008)
Secondary structure: β sheets
Molecular Biology of the Cell (© Garland Science 2008)
Ternary structure
loops
Molecular Biology of the Cell (© Garland Science 2008)
structure-function relations
The majority of proteins perform their biological
functions (catalysis, transcription & translation,
signaling…) only when folded into appropriate
structures (native structures)
Proteins usually exhibit structural
rearrangements when performing their function
Temperature affects protein
structures and motions
high temperatures: proteins unfold, i.e. lose their structures
low temperatures: protein motions are hindered
- There is a certain temperature
window at which a given protein can
function
- Chemical and structural properties of proteins must
be adapted to the temperature at which the organism
thrives
thermophilic
mesophilic
psychrophilic
Thermal stability and
activity of enzymes
Georges Feller 2010 J. Phys.: Condens. Matter 22, 323101
Some proteins are common to
(almost) all organisms
Example:
citrate
synthase
- Bacterium
Arthrobacter
strain DS23R
31 °C
- Pig
37 °C
- archaeon
Thermoplasm 55 °C
a
acidophilum
- archaeon
Sulfolobus
solfataricus
83 °C
- archaeon
Pyrococcus
100 °C
Bell, Russell, et al., European Journal of Biochemistry 269, 6250-6260,
Psychrophiles tend to contain
proteins with:
longer loops: reduced content of prolines (more flexible
backbone); predominance of neutral amino-acid residues
less hydrophobic and less compact cores
larger cavities
higher proportions of surface-exposed non-polar residues
increased lysine-to-arginine rations (weaker hydrogen bonds
and salt bridges)
increased asparagine, methionine and glycine contents
compared to proteins in mesophilic
Thermophiles tend to contain
proteins with:
shorter loops and smaller cavities
more compact & hydrophobic protein core
larger numbers of ionic bonds
increased polarity of water-exposed surfaces
increased arginine-to-lysine contents
increased contents of charged residues and
tryptophan
smaller contents of asparagine and methionine
compared to proteins in mesophilic
“adaptive proteins” have specific functions that allow cells to adapt to its
surrounding environment. Examples: antifreeze proteins.
Enzymes from thermophiles – applications
Example: polymerase chain reaction
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Kary B. Mullis: 1993 Nobel Prize in Chemistry
Enzymes from thermophiles – applications
Example: biofuel production
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cellulosomes
SYMPOZJUM DOKTORANCKIE
Life at extreme temperatures
Bartosz Różycki
IF PAN
November 3, 2016
Temperatures on Earth
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Temperature of the Earth’s surface or clouds (April 2003).
The scale ranges from -81 °C (192 K) to 47 °C (320 K).
The Atmospheric Infrared Sounder (AIRS) instrument aboard
NASA’s Aqua satellite senses temperature using infrared
wavelengths.