Extremophiles

Readings:

1) Wikipedia links: “Extremophile” and “Panspermia”2) Life on the edge: Adventures of an extremophilic scientist: Darlene Lim3) Madigan & Marrs, Extremophiles. Scientific American, April 1997

DefinitionsTypesClues to the origin of life

What are “extremophiles” and where do you find them?”

ExtrEmophilEs

http://www.starwarsholidayspecial.com/images/photos/cantina/cantina_denizens_4.jpg

“Odd forms of life in out of the way places”

“Classic” definition:• A microorganism in the Domain Archaea that thrives

under extreme environmental conditions (temperature, pH, salinity) – Oxford Dictionary of Ecology

The three “domains” of life - Madigan & Marrs, 1997)

AcidophileAlkaliphileEndolith (cryptoendoliths)HalophileHyperthermophileHypolithLithoautotrophMetalotolerant

OligotrophOsmophilePiezophilePolyextremophilePsychrophile/CryophileRadioresistantThermophileThermoacidophileXerophile

“There are many different classes of extremophiles, each corresponding to the way its environmental niche differs from mesophilic conditions. These classifications are not exclusive. Many extremophiles fall under multiple categories. For example, organisms living inside hot rocks deep under Earth's surface are both thermophilic and barophilic.”

http://en.wikipedia.org/wiki/Extremophile#Types_of_extremophiles

Extremophile sub-types according to Wikipedia:

Sub-groups of Extremophiles

• Thermophile

• Hyperthermophile

• Psychrophile

• Acidophile

• Alkaliphile

• Halophile - salt

pH

Temperature

Thermophilic bacteria coloring the hot springs of Yellowstone Park.

http://en.wikipedia.org/wiki/Extremophile#Types_of_extremophiles

Salt Ponds in San Francisco Bay

http://earthobservatory.nasa.gov/IOTD/view.php?id=4877

Salt Ponds in San Francisco Bay

http://en.wikipedia.org/wiki/File:Salt_ponds_SF_Bay_(dro!d).jpg

These ponds are colored by halophilicbacteria that thrive in the hyper-saline environment of these salt evaporation ponds.

http://www.environmentalgraffiti.com/featured/san-francisco-incredible-stained-glass-salt-ponds/14109

Broader definitions:

An “Extremophile” can be any organism found in extreme environments (not just archaebacteria)

Tardigrades (Phylum Tardigrada) are microscopic animals (>1000 spp.) that are found from the Himalayas to the deep seas, and from the

equator to the poles.

Tardigrades are polyextremophiles and are able to survive in extreme environments that would kill almost any other animal. Some can survive temperatures of -273°C, close to absolute zero, temperatures as high as 151 °C (303 °F), 1,000 times more radiation than other animals such as humans, almost a decade without water , and even the vacuum of space. In September 2007, tardigrades were taken into low Earth orbit on the FOTON-M3 mission and for 10 days were exposed to the vacuum of space. After they were returned to Earth, it was discovered that many of them survived and laid eggs that hatched normally, making these the only animals shown to be able to survive the vacuum of space. http://en.wikipedia.org/wiki/Tardigrade

Fig. 3.6Molles & Cahill, 2008

“benthic” = bottom

“pelagic”

Temperature and light penetration with depth further affect productivity and the distribution of organisms

“abyssal”

Molles & Cahill 2008

An ecosystem of chemotrophic organisms at the bottom of the ocean.

Molles & Cahill 2008

Creatures of the deep!

Science, 8 January, 2010

What can we learn from extremophiles?

• Alternate biochemical and physiological adaptations – novel enzymes

– Alternate biochemical pathways (chemosynthesis)

• Clues to the origin of life.

Is the Earth unique?

As far as we know, the Earth is the only planet where life exists.

It is highly unlikely that life (as we know it) exists on other planets in our solar system.

(“Goldilocks” Explanation)

Are other extreme forms of life (“extremophiles”) possible?

What about life on other planets in other solar systems in other galaxies?

What is life anyway?

Organization (low entropy, high information content)

Energy transfer, metabolism

Comprised of cells, membranes

Replication – reproduces on its own

Information content (DNA, RNA…)

Carbon-based

Composed of 25 elements (esp. Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur)

When and how did life originate?

Evidence for Early Life

3.85 BYA – Evidence from Molecular evolution (early life was hot and chemotrophic)

3.8 BYA – Geological evidence (organic deposits in earliest sedimentary rocks)

3.5 BYA – Possible fossil bacteria with organic inclusions

3.2 BYA – Filamentous microfossils

3.0 – 2.7 BYA – Developed bacterial communities (photosynthetic stromatolites)

Raven & Johnson 1992

Earth’s Early Life Forms

Campbell & Reece 2002

Raven & Johnson 1992

“Biological Clock”

˜3.5BYA

˜3.8BYA

˜4.6 BYA

Theories regarding life’s origins:

“Primordial soup” (Miller and Urey’s experiments)

“Panspermia” – “seeding” of organic compounds or organisms from space (analysis of organic molecules in meteorites)

Evidence regarding the early Earth and life’s origins

Early conditions (first 800 MY) were hostile to “life as we know it”bombardment from outer space (accretion)extremely hotvolcanic activity – release SO2no atmosphere

Later conditionsearly atmosphere – lots of CO2, no O2, O3bombardment from outer space

Campbell & Reece 2002

Raven & Johnson 1992

Earth’s Early Energy Sources

The early Earth was a harsh environment, unsuitable for most modern-day organisms (except certain extremophiles?)

The Miller and Urey Experiment (1953) – organic molecules can be made from inorganic ones under the right conditions (believed to resemble the early Earth).

Raven & Johnson 1992

Life abounds in the stranges places…thermal hot springs

Campbell & Reece 2002

… deep sea vents

Campbell & Reece 2002

Theories regarding life’s origins:

“Primordial soup” (Miller and Urey’s experiments)

“Panspermia” – “seeding” of organic compounds or organisms from space (analysis of organic molecules in meteorites)

http://en.wikipedia.org/wiki/Panspermia

Panspermia Hypothesis – the “seeds” of life exist throughout the universe (perhaps as extremophiles!). The Earth was “seeded” by life arriving from space (also called “Exogenesis”).

ALH84001 – the “Mars Meteorite”

Mars

as recounted by A. Tremain at: http://www.lpi.usra.edu/lpi/meteorites/life.html

First reported in McKay et al. 1996, Science 273:924-930

Carbonate Inclusions in ALH84001 – consistent with biochemical processes

http://www.lpi.usra.edu/lpi/meteorites/life.html

Possible Bacterial Fossils in ALH84001

http://www.lpi.usra.edu/lpi/meteorites/life.html

Possible Bacterial Fossils in ALH84001

http://www.lpi.usra.edu/lpi/meteorites/life.html

Possible Bacterial Fossils in ALH84001 – Did life on Earth originate this way?

http://www.lpi.usra.edu/lpi/meteorites/life.html