PHYS2010

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PHYS2010 Life in The Cosmos Extremophiles!
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Question think of an environment on Earth where
life could not exist
It survives in the heavy water in the centre of
nuclear reactors It survives in volcanoes It
survives, even flourishes, at the bottoms of the
Oceans
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Introduction

• What are extremophiles?
• Importance of temperature, pH pressure
• Examples of extreme ecosystems

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What does the word mean?
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Even polyextremophiles!
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?
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?
?
?
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A Extreme drying / drying out of a living
organism
Q What is Dessication ?
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Tardigrades water bears

• The first tardigrades were
• discovered by Goetz in 1773.
• Over 400 species have been described since that
  time.
• Tardigrades grow only to a size of about 1mm, but
  they can easily be seen with a microscope.
• Tardigrade bodies are short, plump, and contain
  four pairs of limbs
• Each limb terminates in four to eight claws or
  discs. They lumber about in a slow bear-like gait
  over sand
  grains or pieces of plant material

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(please dont mention these experiments to the
animal rights people)
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What does extreme mean?

• If a thermophile that normally lives at 100C can
  die at 21C, or a piezophile from the ocean
  bottom dies at surface pressure, what do we mean
  by extreme environment?

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Definitions of extreme

• Different from some fiducial environment?
• Subjective with respect to human preferences?
• Objective with respect to lifes original, but
  UNKNOWN, location ?

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Who is extreme?

• Extreme values of any particular property (pH,
  T, salinity) are simply values far from the
  median for that eco variable
• e.g. water-based life requires ability to
  control cells T, pH, internal solutes (fuel,
  building blocks, etc.), biomolecules, electric
  potential gradients, and be able to repair
  damage. Anything that varies from these
  conditions we regard as extreme

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Role of Temperature

• Solubility of gases goes down as temp goes up
  (impetus for colonisation of land?)
• Organisms have upper temp limits. Chlorophyll,
  proteins and nucleic acid denature at high
  temperatures.
• Enzymes have optimal temperatures for activity
  slow down at low temps.
• At low temp water freezes crystals then break up
  membranes etc. (but the expansion of water to ice
  means layers of ice insulate water below for
  most liquids lakes would freeze from bottom up)

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pH limits
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Rotifers
Complex, multicellular animals with a size range
from roughly 40 microns to over 2,000 microns.
They are in virtually every lake and stream,
every pond, on bits of moss in moist forest, in
the tropics and even in icy arctic terrains
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Grylloblatids Pyschrophiles who live in the cold
on the tops of mountains
Their discoverer was obviously a bit confused by
their appearance The first species named was
Grylloblatta campodeiformis, which means "It
looks like a cricket, a cockroach, and a
Campodea"
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PRESSURE
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This is Life which has never seen The Sun, but
has a completely different energy source many km
below ocean surface (? any old energy will do!!)
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Mars
Surface Temp
210K
Atms Pressure
0.007 bars
Atms makeup
95 CO2
Gravity
38 earth
Other
High radiation levels
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Venus
Surface temp
737K
Atms pressure
92 bars
Atms makeup
96 CO2 sulphuric acid clouds
Surface gravity
88 earth
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Question are we extreme?

• .since oxygen is responsible for significant
  damage (oxidation) to nucleic acids, proteins,
  and lipids, WE are extremophiles! !

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Good news for life elsewhere in the Comos maybe
even in our own solar system
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• What have we learnt thats important for Life in
  the Cosmos?
• Life seems to be able to adapt to very extreme
  environments
• Life can survive for long periods in stasis and
  then recover
• Life can change its environment (oxygen)
• ? more about this in the movie on Monday