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Life at extreme temperatures

Bartosz RóżyckiIF PAN

Warsaw, November 3, 2016

SYMPOZJUM DOKTORANCKIE

Temperatures on Earth

Extreme temperatures on Earth

World Meteorological Organization – the lowest and highest air temperature ever directly recorded at ground level on Earth:

• 56.7 °C (Death Valley, USA, July 1913)

• −89.2 °C (Vostok Station in Antarctica, July 1983)

- geothermally heated water: hot springs (up to 100 °C), deep-see hydrothermal vents (up to ~400 °C)

Life at extreme temperaturesClick to edit Master text styles

Second levelThird level

Fourth levelFifth level

L.J. Rothschild & R.L. Mancinelli, Nature 409, 2001





thermophiles – some like it hot




(Himalayan midge)Nature 310, 1984

psychrophiles/cryophiles – some like it cold

Liquid water on Earth

deep-see hydrothermal vents

Antarctic salt lakes

Tem

pera

ture

[°C

]

500

400

300

200

100

0

Don Juan Pond (Antarctica) does not freeze at -50 °C413 g of CaCl2 and 29 g of NaCl per kg of water

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 life1. Homeostasis (regulation of the internal

environment to maintain a constant state)2. Organization (entities composed of one or

more biological cells)3. Metabolism 4. Growth5. Reproduction6. Response to stimuli7. Adaptation (through natural selection) to

environment in successive generations

Click to edit Master text stylesSecond level

Third levelFourth level

Fifth level

Woese et al., PNAS, 1990

• 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• The deepest rooted organisms are thermophiles

(we live on a microbial planet)




archaea

bacteria

algae

fungi

protozoa

plants

animals


Euka

ryot

es


Himalayan midge (insect) remains active at -16 °CYeast Rhodotorula glutinis can cause frozen food spoilage at -18 °CPlanococcus 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 (micro-animals) can survive a few days at -200 °C

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


Are they loving or just tolerant?Mesophilic organismsExtremeotolerant organismsExtremeophilic organisms

Ø cryophiles live at T < -2 °C Ø psychrophiles grow optimally at T < 10 °CØ thermophiles thrive at T > 45 °CØ hyperthermophile live at T > 75 °C

10 °C < T < 45 °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…

Mic

robi

al G

enom

e Pr

ojec

t D

atab

ase

Example: plant pathogens – bacteria – found in the stratosphere

Living organisms are sensitive to temperature changes



Fifth level

Temperature (°C)

Gro

wth

rat

e

extremeophilic microorganisms

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 acidsincreased 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 crystalsenzyme kineticsdecreased fluidity of cellular membranes (liquid-gel transition of lipid membranes)

How have the living organisms adapted to extreme temperatures?

Molecules of life

Molecular Biology of the Cell (© Garland Science 2008)

mol

ecul

ar m

ass

Water

NASA

Polarity


Polarity


1D=3,33564 10-30 C m

molecule [D]H2O1,85HCl 1,08CO 0,117O2

0

Polar molecules, such as H2O, have a permanent dipole moment

Are they scared of water? C-C and C-H bonds are non-polar

Oils consists of hydrocarbons

hydrophobic

Example: hydrocarbons

Hydrogen bonds



Hydrophilic

ions

electrostatic interactions

polar molecules

hydrogen bonds


Hydrophobic

• Water molecules do not form hydration layers around such molecules


Hydrophobic effect

Hydrophobic molecules tend to contact one another…

… because of the entropy of water

BioMacroMolecules LipidsNucleic acids (RNA & DNA)Proteins

Lipids: it is a matter of heads and tails

lipid bilayer

phos

phol

ipid

lipids are amphipathic molecules

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.

Lipid membranes of psychrophiles

Challenge: sustain membrane fluidity at low temperatures (fluid-gel transition)

Challenge: sustain membrane fluidity at low temperatures (fluid-gel transition)



Fifth level

Unsaturated lipids

• reduced size of the head groups

• increased (poly)unsaturated to saturated lipid ratios

• shorter tails

Lipid membranes of psychrophiles

Lipid membranes of thermophiles



Fifth level

Challenge: prevent membrane damage at high temperatures

Nucleic acids


Nucleic acids: everyone pair up!po

lynu

cleo

tide

Base pairs

DNA melting - things are unraveling fast

T < Tm

T > Tm

DNA melting - three are better than two

T < Tm

T > Tm

Tm depends on the fraction of the G:C base pairs, which have 3 hydrogen bonds

increased G:C fractions are found in the DNA of prokaryotic thermophiles

Genetic code

DNA

transcription (polymerase)

RNA

translation (ribosome)

proteins

3 base pairs – codon – one amino acid

DNA codon table (Wikipedia)

The central dogma of molecular biology

DNA melting - with a pinch of salt

G:C fraction (Biochemistry 43, 3537-3554, 2004)

mel

ting

tem

pera

ture

Tm

(°C

)

T < Tm

T > Tm

Tm depends on the fraction of the G:C pairs in the DNA molecule, and also on the salt concentration in the 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.

Biochemical Society Transactions 31, 58-63, 2011

Wikipedia

Amino acids


amino group

carboxylgroup

polypeptides

Protein secondary structure: amino acid sequence


Secondary structure: α helices


Secondary structure: β sheets


Ternary structure


loops

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 structureslow 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

Thermal stability and activity of enzymes

Georges Feller 2010 J. Phys.: Condens. Matter 22, 323101

psyc

hrop

hilic

ther

mop

hilic

mes

ophi

lic

Some proteins are common to (almost) all organisms

Example: citrate

synthase

- Bacterium Arthrobacter strain DS2-3R

31 °C

- Pig 37 °C

- archaeon Thermoplasmaacidophilum

55 °C

- archaeonSulfolobus solfataricus

83 °C

- archaeonPyrococcus furiosus

100 °CBell, Russell, et al., European Journal of Biochemistry 269, 6250-6260, 2002

Psychrophiles tend to contain proteins with:

longer loops: reduced content of prolines (more flexible backbone); predominance of neutral amino-acid residuesless hydrophobic and less compact coreslarger cavitieshigher 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 organisms

shorter loops and smaller cavitiesmore compact & hydrophobic protein corelarger numbers of ionic bondsincreased polarity of water-exposed surfacesincreased arginine-to-lysine contents increased contents of charged residues and tryptophansmaller contents of asparagine and methionine

compared to proteins in mesophilic organisms

Thermophiles tend to contain proteins with:

“adaptive proteins” have specific functions that allow cells to adapt to its surrounding environment. Examples: antifreeze proteins.

Enzymes from thermophiles – applicationsExample: polymerase chain reaction



Fifth level

Kary B. Mullis: 1993 Nobel Prize in Chemistry



Fifth level

Enzymes from thermophiles – applicationsExample: biofuel production

cellulosomes

Life at extreme temperatures

Bartosz RóżyckiIF PAN

November 3, 2016

SYMPOZJUM DOKTORANCKIE

Temperatures on EarthClick to edit Master text styles



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.

life at extreme temperatures - ifpan.edu.pl · strain 121 (geogemma barossii, archaea), found near...

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