Transcript Document

Extreme Environments
Extremes in terms of what human life
can exist in.
These can include temperature (high
or low), pressure, acid or alkali and
high salts.
DEEP SEA
Open ocean the photic zone can extend to 300m, causing a good deal
of biological growth down to 1,000m.
Below this level (75% of ocean volume) the biological activity is less.
3 problems are faced
Low temperature below 1,000m it is a constant 2-30C
High pressure 1 atm/10m. eg at 1,000m it is?
Low nutrient levels
Phytoplankton falls to the sea bed as ‘marine snow’ which is seasonal
following growth. The journey down takes over 1 month and 99%
is already decomposed.
Below 100m the bacteria are psychrophilic. Some bacteria isolated
are barotolerant (down to ~ 300m), grow at atmospheric pressure,
will not grow above 500atm.
4,000m to 6,000m are barophilic.
Grow optimally at 400atm, still grow at 1 atm.
From deeper waters get extreme (obligate) barophiles,
optimally at 700-800atm. Not killed at 1atm, but very heat sensitive.
Inc pressure decreases binding capacity of enzymes, so enzymes
are folded in such a way as to minimise this.
The membranes have an increase in the amount of unsaturated
fatty acids in their membranes to keep the membrane fluid.
They grow slowly as chemical reactions are slowed down.
The have special high pressure porins expressed at high pressures.
This and a few other genes are specifically expressed at high pressures
Temperature
Classes
Psychrophile – hyperthermophiles
Growth at cold temperatures.
Psychrophile opt growth below 150C and max below 200C, grows at 00C.
Psychrotolerant grows at 00C but opt 20-400C.
Psychrophiles found in any permanently cold environment,
can be rapidly killed by room temp. Best known are algae that grow
in the bottom of sea ice in polar regions. Growing in summer months
on the bottom of ice ~ 2m thick.
In summer months also get alga growing under the surface of snowfields
and glaciers giving it a red or green colour.
Summer
snow algae
Psychrotolerant are found in water, milk, coconut water,
soil and lots of other foods kept in a fridge. Growth is slow.
These include bacteria, fungi, algae and protozoa.
Psychrophilic enzymes have lower temp optimums and are
denatured at moderate temperatures. More alpha helix and less beta
sheet making them less rigid. More polar and less hydrophobic aa,
to help keep protein flexible. More unsaturated fatty acid.
Sampling bacteria
in Antarctica
High temperature environments are associated with
hot springs and hydrothermal vents
Water can pick up a lot of minerals from the hot rocks
and have various pH’s.
Above 700C there is very little Oxygen.
The nutrients support a range of chemoorganotrophic
and chemolithotrophic bacteria.
As water flows away from the spring it cools down and you
get a temperature gradient.
This supports a range of bacteria including cyanobacteria below 740C.
As the temperature cools further, eukaryotic organisms can grow
like the thermoacidophilic alga Cyanidium Caldarium temp max 560C.
One very common aerobic organism are Thermus
species which are aerobic chemoorganotrophs.
They have a temp optimum ~700C. This is near
the limit of aerobic growth, why?
The max temp that eubacteria have been isolated
have been at 950C.
The only bacteria that have been found growing above
this temp are archebacteria.
Hydrothermal Vents.
Associated with moving tectonic plates on the ocean floor.
Hot basalt and magma near the sea floor.
Seawater seeping into it becomes superheated and rich in minerals.
Two types of vents.
Warm vents 6-230C and hot vents.
Hot vents emit at 270-3800C.
The mineral rich liquid forms ‘black smokers’
as the mineral rich liquid mixes with cold water.
Vent
Minerals
Tubeworms
And Mussels
Vent video
Tubeworm video
Energy source.
The vent fluid has a high conc. of H2S, Mn2+, H2, CO, NH4+ .
These are used as inorganic energy sources by chemolithotrophs.
CO32- and HCO3- is fixed into organic carbon.
There are large # sulphur oxidising bacteria, Thiobacillus, Thiothrix
and Beggiatoa, fixing CO2 at expense of H2S and S2O32-.
Nutrition of animals.
Chemolithotrophs live in symbiotic association with animals
in the thermal vent. The 2m long tube worms have a modified gut
with spongy tissue – trophosome (50% of it’s weight) loaded with
S granules and large # S oxidising bacteria.
These bacteria nourish the worm with excretion products and
dead cells. The worm is red with blood (special Hb) that traps
H2S, CO2 and O2 for the bacteria.
Tubeworms
And Mussels
Hydrothermal fluid is emitted at 270-3800C,
could theoretically have bacteria there.
At 2,600m water boils at 4500C.
Hyperthermophiles are known to live around the the plume
coming from the chimney formed from the ppt minerals.
The walls of the chimney are colonised by Methanopyrus
oxidising H2.
Pyrolobus has been isolated from the plume growing at 1130C,
but may be able to grow at higher temps.
Vent chimneys are colonised by the 6cm metazoan
worm Alvinella or Pompeii worm.
Pompeii
worm
pH
Organisms have optimum pH values for growth.
Most microorganisms are neutrophiles pH opt 5.5-8.
Bacteria cannot survive if the internal pH drops below ~ 5.0.
Acidophiles must maintain an internal pH above this or their
proteins will denature. There membranes can be impermeable
to protons. Thiobacillus are important acidophiles that oxidise
sulphide minerals generating sulphuric acid, they are used to help
leach Cu from low grade ore.
They cause environmental problems of acid mine drainage from
coal mining waste, acid and dissolved metals are toxic (inc Al).
They need air to oxidise the pyrite, so coal below the surface is OK.
Cyanidium caldarum and Sulfolabus acidocaldarius live in
acidic hot springs.
Acid mine
Drainage
From coal mine
Osmotic – Halophiles.
The water availability (activity) is also dept. on the conc. of solutes.
The cytoplasm of cells usually has a higher solute conc. than the
surrounding media so water tends to move in, balanced by cell wall..
Seawater 3.5%, marine organisms have a requirement for Na+.
At high solute conc. water will tend to move out
Mild halophile 1-6%
Moderate 6-15%
Extreme halophile 15-30%
Organisms cope by using internal solutes, often organic compounds
like glycine betaine, proline or glycerol to balance the osmotic
pressure without damaging proteins or K+ (Halobacterium).