Transcript Extreme Biology - We don't just talk. We deliver

Topics:
 Types of extreme environments present on Earth
 Adaptations to cell structures required for survival in extreme
environments
 Residents of extreme cold environments
 Residents of hydrothermal environments
 Residents of acidic environments
 Residents of high salt environments
 Residents of alkaline environments
 Survival under conditions of high-level radiation exposure
 Importance of extremophiles
Universal Tree of Life: 3 Domain System
Bacteria and Archaea are
both prokaryotes
Extreme Environments on Earth
1.
Sea Ice (extreme cold)
2.
Hydrothermal vents (extreme heat and high metal content)
3.
Sulfuric Springs (extreme heat and highly acidic)
4.
Salt Lake (extreme salt concentrations)
5.
Soda Lake (extreme salt concentration and highly alkaline)
Cellular Targets of Adaptations to Extreme
Environments
Typical Prokaryotic Cell
Cytoplasm: water,
Nucleoid: Aggregated
proteins, metabolites,
salts
DNA Chromosome
Typically lipid bilayer
Life on Ice
 Over 75% of Earth’s biosphere is
permanently cold (< 5°C)
 Much of the life present in the cold
environs is planktonic growth of bacteria
and archaea in frigid marine waters (~104
cells/ml) (psychrophiles)
 Identified using rRNA techniques
– 16S rRNA sequencing
– Fluorescent rRNA DNA probes
 At this point physiology of psychrophilic
archaea/bacteria undetermined
 Cold adaptations: more fluid membranes,
more structurally flexible proteins
Psychrophilic cyanobacteria
Methanogenium
frigidum
Adaptations to Extreme Cold: Making More
Fluid Membranes
More fluid membranes result from putting unsaturated/polyunsaturated fatty acids into
the membrane
More Life on Ice: Algae
Algae living on the ice
(photosynthetic unicellular plant)
Lichen = symbiotic relationship
between algae and fungi
Phytoplankton
Krill
Polychaete Worms Living on Methane Ice
 It is thought that the worms eat the bacteria that are growing on
the methane ice
Lake Vostoc: A model for Life on Europa?
Hydrothermal Vent Systems
Anatomy of A Vent
Hydrothermal Vents: Abiotic Conditions
 Extremely hot temperatures (> 350ºC [hydrostatic pressure of 265 atm
prevents water from boiling until 460 ºC ])
 Extremely high pressures up to 1,000 atm
 Vents rich in minerals (eg. Iron oxides, sulfates, sulfides, manganese
oxides, calcium, zinc, and copper sulfides)
 Hot waters anaerobic since solubility of oxygen decreases as water
temperature increases
Hydrothermal Vents: Biotic Community
 Archaea and bacteria grow in or near vent chimneys, shown to
live and reproduce at temp. of 115°C (hyperthermophiles)
 As of 5 years ago believed highest upper temp. for life was 105
°C, now expect hyperthermophiles may grow up to 160 °C [limit of
ATP stability]
 Rich microbial communities grow at some distance from vent
chimneys where temperatures are more moderate (8 - 12°C) due to
mixing mixing with cold seawater (~2°C)
Hydrothermal Vent Ecosystems: The Prokaryotes
Bacteria
Archaea
Methanococcus
janaschii (85°C)
Pyrococcus furiosus
(100°C)
Vent contact slide
Archaeoglobus fulgidus
(83°C)
Aquifex aeolicus (95°C)
Thermotoga maritima (90°C)
Thermal Adaptations Used By Hyperthermophiles for
Survival
 Membrane: ether-linked membrane-lipids,
monolayer membranes
 Protein: hydrophobic protein core, salt
bridges, chaperonins
 DNA: Cation stabilization (Mg2+), Reverse
DNA gyrase, DNA-Binding proteins (histones)
 General: compatible solutes?
Histone and DNA
Hydrothermal Vent Ecosystem: Tube Worms
Vestimentiferan worms; Riftia pachyptile
 Vent water is ~350o C with high H2S concentrations
 Surrounding water is ~10-20oC
 Gutless tubeworms (Riftia have a mutualistic symbiosis with aerobic
H2S- oxidizing bacteria (Thiomicrospira).
Endosymbiosis in Tubeworms
Hydrothermal Vent Ecosystems: Bivalves
Calyptogena magnifica
Bathymodiolus thermophilus
Hydrothermal Vent Ecosystems: “Snow
Flurries” and Crabs
Flocs of sulfur bacteria
Galatheid crabs
And Where There’s Crabs, Octopi Are Not Far Behind
Continued
Topics:
 Types of extreme environments present on Earth
 Adaptations to cell structures required for survival in extreme
environments
 Residents of extreme cold environments
 Residents of hydrothermal environments
 Residents of acidic environments
 Residents of high salt environments
 Residents of alkaline environments
 Survival under conditions of high-level radiation exposure
Importance of extremophiles
Extreme Environments on Earth
1.
Sea Ice (extreme cold)
2.
Hydrothermal vents (extreme heat and high metal content)
3.
Sulfuric Springs (extreme heat and highly acidic)
4.
Salt Lake (extreme salt concentrations)
5.
Soda Lake (extreme salt concentration and highly alkaline)
Life in Sulfur Springs (Hot and Acidic)
Abiotic conditions:
- high temperatures >30°C
- low pH (< 4)
- high sulfur
 Sulfur-oxidizing, acid-loving,
hyperthermophiles such as the
archaeon Sulfolobus have been
isolated from sulfur hot springs
Sulfolobus grows at 90oC, pH 1-5
–Oxidizes H2S (or So) to H2SO4
–Fixes CO2 as sole C-source
 Acidophiles do not have low
internal pH’s and have adapted to
keep protons outside the cell
Other Acidic Environments and Denizens
Acid mine drainage
 Acidophilic archaeon, Picrophilus
oshimae, grows optimally at pH 0.7,
cannot grow above pH 4
 Red alga Cyanidarium caldarium grows
at pH of 0.5
 Archaeaon Ferroplasma acidarmanus
thrives in acid mine drainage at pH 0 (has
no cell wall)
 Acidophiles studied to date appear to
have very efficient membrane-bound
Na+/H+ pumps and membranes with
low permeability to protons
High Salt Environments
 Low biodiversity; only home to halophilic
organisms belonging to Archaea, Bacteria and
some algae
Salt evaporation ponds
Great Salt Lake
 Extreme halophiles require at least 1.5 M
NaCl for growth (most need 2 – 4 M NaCl for
optimum growth)
 Cell lysis occurs below 1.5 M
 Membranes are stabilized by Na+
 Maintain high internal K+Cl- to balance high
external Na+Cl A number of halophiles have a unique type of
“photosynthesis”
 Multiple light-sensitive proteins
–Halorhodopsin (Cl- transport, creating Clgradient which drives K+ uptake)
–Bacteriorhodopsin (photosynthesis?)
Halophilic Algae
 Photosynthetic flagellate
 Red because of high
concentrations of beta-carotene
 On sensing high salinity, pumps
out Na+ ions and replaces with K+
ions
Dunaliella salina
 In high salt, will alter
photosynthetic pathway to produce
glycerol (water-soluble, nonionic
substance which prevents
dehydration) instead of starch
Halobacterium
salinarum and Lightmediated ATP
Synthesis
Halobacterium salinarum
 Halobacterium contain
photopigments which are
used to synthesize ATP as
a result of proton motive
force generation
Retinal chromophore of
bacteriorhodopsin
trans-form
light
cis-form
High Salt Alkaline Environments: Soda Lakes
 Have very high pH (> 9) due to high
levels of CO32- ion
 Very few organisms can tolerate
alkaline conditions (to date only
alkalophilic prokaryotes have been
isolated)
Lake Magadi (Soda lake in Kenya)
 Most alkalophilic organism,
cyanobacterium Plectonema, grows at
pH of 13
 Alkalophile adaptations: pumps to
pump out OH-, efficient Na+/H+ to
provide internal H+, modified
membranes
Cyanobacterium
Spirilina
Natronobacterium
Survival Under Conditions of High Level
Radiation Exposure: Deinococcus
radiodurans
 Aerobic, mesophilic bacterium
 Extremely resistant to desiccation, UV and ionizing
radiation
-- Can survive 3-5 million rads (100 rads is lethal for
humans)
 Contain variable numbers (4-10) of chromosomes
DNA Damage Repair in Deinococcus radiodurans
 Deinococcus
radiodurans has
very efficient DNA
repair machinery
 DNA sheared by
radiation will
reform within 24h
Importance of Extremophiles:Extremozymes
 Enzymes from extremophiles offer
some important potential benefits:
 Hyperthermophiles
– Sugar conversions without microbial
growth and contamination
 Psychrophiles
– Modification of flavor/texture of foods
without microbial growth & spoilage
 Acidophiles
– Removal of sulfur from coal & oil
 Alkalophiles
– Cellulases that can be used in detergents
Importance of Extremophiles: Astrobiological
Implications
 Extreme environments on Earth are
thought to be very similar to extreme
environments that exist elsewhere in space
 Microorganisms that thrive in Earth
extreme environments are thought to be
likely candidates for the types of biota that
may exist in extraterrestrial habitats
Mars
 Mars is postulated to have extremophilic
regions including permafrost,
hydrothermal vents, and evaporite crystals
 Europa is thought to have a subsurface
ocean
Europa