Download Extremophilic microorganisms and the physico-chemical limits

Extremophilic microorganisms and
the physico-chemical limits of life
Helga Stan-Lotter, University of Salzburg, Austria
New classification of organisms - Bacteria, Archaea
and Eukarya
Extreme environments: their physico-chemical
parameters
Molecular adaptations to extreme environments
Growth versus survival
Origin of Life ?
Prokaryote
World
Multi-cell
Life
1
Man
First
Eukaryotes
0.01
First
Invertebrates
2
PO (atm)
0.1
0.001
0.0001
0.00001
4.5
4
3.5
3
2.5
2
1.5
Time before Present (Ga)
1
0.5
0
Eukaryotes - Prokaryotes (1931)
/
Eubacteria
(Bacteria)
\
Archaebacteria (1977)
(Archaea)
Prokaryote
World
Multi-cell
Life
1
Man
First
Eukaryotes
0.01
First
Invertebrates
2
PO (atm)
0.1
0.001
0.0001
0.00001
4.5
4
3.5
3
2.5
2
1.5
Time before Present (Ga)
1
0.5
0
Venus
Mars
Viking lander approaching Mars (painting)
1996
Staphylococcus aureus
Vibrio cholerae
Cyanobacteria
Spirulina species
Amoeba (protozoon)
Unicellular algae
(unicellular diatom)
Extreme environments
are hostile to human life and were thought
to be uninhabitable by other organisms.
(Richard Johnson)
Extreme habitats
are environments with a restricted species
diversity and the absence of some
taxonomic groups
(Thomas D. Brock)
Extreme physico-chemical factors:
Temperature - high,
low
Pressure - high
pH value - high; low
Salinity - high
Water activity - low
Ionizing radiation - high
Toxic substances - high concentrations
Nutrients (carbon, other) - low concentrations
Survival versus Growth
Spores, endospores, cysts, seeds
(resting stages):
Unicellular bodies, produced by plants, fungi, and some
microorganisms.
Often a resting stage is encased in a protective coat, adapted
to resist heat, desiccation, or other unfavorable environmental
conditions.
Hot environments on Earth
Thermophiles and
Hyperthermophiles
Adaptations
Hot spring (Yellowstone)
Solfatara field in Yellowstone (USA)
Grand Prismatic Spring (Yellowstone)
Sulfur spring, pH 1.8-2.2
S-layer
(surface)
Solfatara field on Kraffla mountain
(Iceland)
Mud geysir (Iceland)
Solfatara field (Iceland)
Pyrodictium occultum
Self-heating coal refuse piles
(Habitat of Thermoplasma acidophilum)
Black smokers and hydrothermal
vents
Many hyperthermophilic Archaea are
chemolithotrophic.
Their energy sources are anorganic
substances, e.g.
H2, So, FeS2, FeCO3
Scheme of the universal lipid bilayer membrane
Membrane lipids of hyperthermophiles often consist of
isoprenoid tetraether structures; these are more resistant to
heat and acid than ester bonds and fatty acids
Psychrophiles
Temperature and growth
Salty environments on Earth
(high salinity, low water activity)
Halophilic
and halotolerant prokaryotes
Adaptations
Swakopmund salterns (Namibia)
Permian salt sediments
Bore cores from salt sediments
(600 m below surface)
Haloarchaeal colonies on M2 agar
Halococcus salifodinae, an archaeal isolate
from Permian salt
High radiation;
high concentrations of toxic substances
Radiation resistant
metallo-tolerant, toxitolerant
Adaptations
Biologically efficient radiation dosis (in Gray):
1 Gy = 1 Joule absorbed energy per kg of tissue
Lethal dosis
Humans
Salmonella, Bacillus sp.
Deinococcus radiodurans
5-10 Gy
2.000 - 6.000 Gy
> 30.000 Gy
Deinococcus radiodurans
possesses an extremely efficient DNA repair system;
can excise and repair misincorporated bases;
can repair breaks in single- or double-stranded DNA;
can reassemble its chromosome from fragments.
Metallo-tolerant, toxi-tolerant
microorganisms:
Efflux pumps (ATPases)
Low concentrations of nutrients:
Deep subsurface
Oligotroph,
thermotolerant, metallo-tolerant
Deep terrestrial
subsurface
Bacterial endospore
Tardigrade, moving
Tardigrade, dry
Tardigrades:
up to 2.3 % of dry weight: Trehalose
Relevance for the origin of life ...?
(Hypothesis paper by Cleaves II & Chalmers,
Extremophiles may be irrelevant to the origin of life.
Astrobiology 4: 1, 2004)
Summary
Microorganisms thrive in extreme environments which once were believed
entirely hostile to life
Extreme environments are characterized by one or several physico-chemical
parameters
Extremophilic microorganisms survive exposure to space conditions,
desiccation, and low nutrient environments - all this perhaps for millions of
years. They may therefore survive also space travel.
However, many extreme environmental parameters are not compatible with
ideas about the origin and early evolution of life (see Cleaves and Chalmers,
2004).