Extremophiles and extreme environments
EXTREMOPHILE = phile “love for”
Love for extreme environments
Hyperthermophiles=love for high temperatures
Psychrophiles=love for low temperatures Acidophiles=love for acid conditions
Baroextremophiles=love for high pressures
Halophiles=love for high salty conditions
Where do we find those extreme conditions ?
Hydrothermal vents
Hot springs
In these areas the P is high (several atm) and T> 350 C, water is still liquid.
Dry valleys of Antarctica
Here T< 0 C, water is liquid only locally when ice melts Interior of sediments
Here T gets warmer with
depth and water is inflitrated
Nuclear reactors
Salty lakes
D. radiodurans
Mono lake, CA
Areas where there
is high radiation
Interior of
rocks
Concentration of
salts is very high
Columbia river basalt
Organisms living in these areas are called endoliths
BASIC METABOLIC NEEDS FOR LIFE
A liquid environment where chemical reactions can occur
WATER
A source of raw materials to build more complex molecules
THE CARBON SOURCE
A source of energy to fuel reactions (by means of producing ATP)
THE ATP SOURCE
All living cells use ATP to store and release energy
for all their metabolic reactions
Animals get both of these sources through food
Plants get their C source from CO2 and their energy source from light
But micro-organisms have a variety of C and energy sources
that differ from the two above.
Metabolic
classification
photo-autotrophe
Energy
source
sunlight
Carbon
source
CO2
photoheterotrophe
sunlight
chemoautotrophe
Inorganic
chemicals (Fe,
S, NH3)
Organic
compounds
(food)
CO2
chemoheterotrophe
Organic
chemicals
(food)
Example
Plants & photosynthetic bacteria
Some bacteria & archea
Some bacteria and archea
(specially in extreme
environments)
Organic
Animals, fungi & many microbes
compounds
(food)
All metabolic pathways (classification in table) require
liquid water.
So, what limits whether there is life or not on an environment is
not the source of energy or the source of carbon, but rather
whether water can be in liquid state.
We find life only in places where
water can exist in liquid state
The energy available for life is not the same energy
used to have water in liquid state
HEAT
The Reactions that supply energy for life
are called REDOX reactions
Redox reaction involve transfer of electrons between the reactants
For example
The reaction can be
decomposed
As follows
H2 + ½ O2
H2
2 H+ + 2e- + ½ O2
H2O
2 H+ + 2eH2O
Electrons are being transferred from hydrogen to oxygen,
and this supplies energy that can be used for other
chemical reactions
Many organisms do not use sunlight or organic molecules
to obtain their energy, yet they do redox reactions
EXAMPLES
1 Combining iron and water to obtain energy
2Fe2+ + ½ O2 + 2H+
2Fe3+ + H2O
2 Combining sulfur, CO2 and water to obtain energy
Sulfide oxidation
Elemental sulfur
CO2 + 2H2S
CH2O + 2S + H2O
2CO2 + H2S + 2H2O
2(CH2O) + H2SO4
Sulfide oxidation
Sulfate (or sulfuric acid)
BAROPHYLES
Amphipods are shrimp-like animals belonging to
the order crustacea. They can live in the ocean
or in the land. They measure between 5-20 mm in
length.
These animals can live, like some sea cucumbers, nematods (worms), crabs and
bacteria, at the bottom of the deepest part of the ocean floors. They resist
very high pressures. To survive they have several cellular adaptations:
Flexible cell membranes, they use an organic molecule called trimethylamine
oxide to help enzymes fold properly.
Source of carbon: heterotrophe
Source of ATP: food
Tardigrades (water bears): tiny invertebrates that live
everywhere from fresh water to marine habitats and
from lichens in city gardens to the top of mountains.
They have the ability to curl up, switch off their
metabolism and wait for conditions to improve.
They hold the record for surviving several kinds
of extreme environments in dormant
conditions:
Hydration: without water for 120 years
Temperature: 0 to -272 OC and from 0 to 151 OC
Vacuum space: lived on board of ESA experimental satellite
Pressure: 6,000 atm
Radation: X ray and Gamma tolerance
Source of carbon: heterotrophe
ATP source of energy: chemical (food)
Psychrophiles
Arctic springtails: insects. They lower the freezing point
of their body fluids using an anti-freeze. They also use
cryoprotectants (sugars and glycols), these are molecules
that envelope the cell components to avoid damage by
the freezing process
Western painted turtle
North America wood frog
They use antifreeze to protect
their body and allow control
freezing in their cavities
Antarctic nematode
Freezes its cell cytoplasm, blood and other
Body liquids, and only keeps its cell nuclei
Unfrozen, by synthesizing a cryo protectant
Source of carbon: heterotrophes
Source of ATP: food
Endoliths
Bacteria live inside rocks found in the deep subsurface
(500 m and deeper).
Some protozooan too. They eat bacteria. They move between the
Rocks using their flagella
Protozooan: heterotrophs eat bacteria to produce ATP and use oxygen as source of
energy
Bacteria: autotrophs, they respire oxidized forms of sulfur, iron and manganese
to obtain their energy. They eat organic material dissolved in sediments to
produce ATP. Some bacteria use acetate as both sources of carbon and energy
Columbia River Basin, WA
These are igneous rocks where there
is no buried organic material.
Bacteria manufacture their organic material (methane) by using C and H taken
From CO2 and H2 dissolved in the rocks
CH4 + O2
CO2 + 2H2
Hyperthermophiles
Pyrolobus fumari, bacterium
Can live at 113 oC, inside hydrothermal vents
It has modified its enzymes so that they are stable
At high temperatures
Chemoautotrophe (chemolithotrophic)
Source of carbon=CO2
Source of energy= H2 gas
Source of ATP=NO3, O2, SO3
Halophiles
They resist high concentrations of salts. Osmosis normally dehydrates
The cells in non-halophilic organisms. Halophiles can resist and counteract
Dehydration by accumulating large quantities of solutes inside their cells
Halobacterium is an archea organism.
Source of ATP: they breathe O2 and organic material
Source of carbon:organic material (amino acids)
chimioheterotrophes
Achromatium is an archea bacterium
Source of carbon: CO2
Source of ATP: they breathe O2 and oxidize H2S and
S converting it to sulfate
O2 + H 2 S
SO3 + H2O
Acidophiles
Organisms that thrive in acidic environments,
such as the ones found in geysers and hot springs
Picrophilus is an archea organism
Who lives in environments of pH 0.7-0.
This micro-organism has a cell membrane with low
Proton permeability, a high acid stability.
It is strict aerobic (breathes O2)
It has genes to produces enzymes to protect the membrane from
Oxidative damage
Source of ATP: heterotrophus uses organic materials for food
Source of carbon: organic materials
Alkaliphiles
These are organisms that like living at pH conditions of 12,
Like the ones found in soda lakes.
Natronomonas archea bacterium, heterotrophe
They have cell membranes capable of pumping protons
across so as to maintain a lower pH inside the cell.
Energy and ATP source= O2 respiration
Source of C= amino acids (organic molecules)
Dry lovers
Bacterium Chroococcidiopsis is
A cyanobacterium, it is
photosynthetic
Atacama Desert, Chile, it rains a few times/century.
Source of C= CO2
Source of ATP= sunlight
It makes spores and when water is available
resumes growth
Metallophilics
Organisms who like heavy metals like zinc,
arsenic and cadmium
and also uranium
Geobacter is a eubacterium. It eats uranium and other metals.
It converts dissolved uranium
Into a solid form.
Anaerobic
Chemoheterotrophe
Source of energy= Fe and other metals
Source of C=organic materials
CHO
Fe
+ O2
CO
2
+ H2O
Used for cleaning
Contaminated soils
Radiation-resistant organisms
Deinococcus is a bacterium which stands 1,000
times radiation levels
that otherwise would kill humans
Radiation resistance comes from two moalities that this organisms
Has developed: it has several copies of the same gene and it can repair its
DNA very fast thanks to special porteins
Aerobic, chemoheterotrophe
Source of energy=O2
Source of carbon=organic material
Source of ATP=organic molecules
Biotechnology applications of extremophiles I
Methanococcoides burtonii is a psychrophile (loves cold), archea, lives at the bottom of
Lakes in Antarctica
It makes CH4 under anaerobic conditions from organic materials and CO 2
It can be useful for climate and global warming control
It can be useful for the production of fuel
Biotechnology applications of extremophiles II
Deinococcus radiodurans is genetically engineered for the
bioremediation of solvents and heavy metals. An engineered
stain of Deinococcus radiodurans has been shown to degrade
ionic mercury and toluene in radioactive mixed waste environments
It can be used to clean up radioactive waste, solvents
and heavy metals contaminated soils
Biotechnology applications of extremophiles III
anerobic sulfate reducing bacteria, which
are know to live in hyper-saline lagoons in Brazil and Australia
Sulfate-reducing bacteria (SRB) comprise several groups of
organisms that use sulfate as an oxidizing agent, reducing it to sulfide.
Sulfate-reducing bacteria can be used as a possible way to deal with acid
mine waters.
Acidithiobacillus thiooxidans consumes sulfur and produces sulfuric acid.
This bacterium in conjunction with others of the same genus is currently
used in a mining technique called bioleaching whereby metals are extracted
from their ores through oxidation. The bacteria are used as catalysts.
T=20 K= ­ 253 C= ­423 F
Surveyor, an unmanned lunar probe landed on the Moon in 1967 and left a camera on its surface.
31 months later, in 1969, two astronauts from the Apollo manned mission recovered
the camera and other devices from Surveyor and brought it back to Earth.
NASA scientists examined the camera and found
that the polyurethane foam insulation covering its
circuit boards contained 50 to 100 viable specimens
of Streptococcus mitis, a harmless bacterium commonly found in the human nose, mouth, and throat.
http://science.nasa.gov/newhome/headlines/ast01sep98_1.htm
The bacteria were found in the form of spores.
Spores=dormant state of some bacteria
This story takes us back to the theory of Panspermia
and the possibility of us contaminating space with
terrestrial life
This variety of extremophiles suggests that
life may be possible in many more places than we
would have guessed. This expands the range of candidate planets where we should search for ET life.