Extreme Biology

1

2
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

3
Universal Tree of Life 3 Domain System
Bacteria and Archaea are both prokaryotes
4
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)

5
Cellular Targets of Adaptations to Extreme
Environments
Typical Prokaryotic Cell
Cytoplasm water, proteins, metabolites, salts
Nucleoid Aggregated DNA Chromosome
Typically lipid bilayer
6
Life on Ice

• Over 75 of Earths biosphere is permanently cold
  (lt 5C)
• 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
7
Adaptations to Extreme Cold Making More Fluid
Membranes
More fluid membranes result from putting
unsaturated/polyunsaturated fatty acids into the
membrane
8
More Life on Ice Algae
Algae living on the ice (photosynthetic
unicellular plant)
Lichen symbiotic relationship between algae and
fungi
Krill
Phytoplankton
9
Polychaete Worms Living on Methane Ice

• It is thought that the worms eat the bacteria
  that are growing on the methane ice

10
Lake Vostoc A model for Life on Europa?
11
Hydrothermal Vent Systems
12
Anatomy of A Vent
13
Hydrothermal Vents Abiotic Conditions

• Extremely hot temperatures (gt 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

14
Hydrothermal Vents Biotic Community

• Archaea and bacteria grow in or near vent
  chimneys, shown to live and reproduce at temp. of
  115C (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 - 12C) due to mixing mixing with
  cold seawater (2C)

15
Hydrothermal Vent Ecosystems The Prokaryotes
Bacteria
Archaea
Methanococcus janaschii (85C)
Vent contact slide
Aquifex aeolicus (95C)
Pyrococcus furiosus (100C)
Archaeoglobus fulgidus (83C)
Thermotoga maritima (90C)
16
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
17
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).

18
Endosymbiosis in Tubeworms
19
Hydrothermal Vent Ecosystems Bivalves
Calyptogena magnifica
Bathymodiolus thermophilus
20
Hydrothermal Vent Ecosystems Snow Flurries and
Crabs
Flocs of sulfur bacteria
Galatheid crabs
21
And Where Theres Crabs, Octopi Are Not Far Behind
22

Continued
23
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

24
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)

25
Life in Sulfur Springs (Hot and Acidic)

• Abiotic conditions
• - high temperatures gt30C
• - low pH (lt 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 pHs and
  have adapted to keep protons outside the cell

26
Other Acidic Environments and Denizens

• 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)

Acid mine drainage

• Acidophiles studied to date appear to have very
  efficient membrane-bound Na/H pumps and
  membranes with low permeability to protons

27
High Salt Environments

• Low biodiversity only home to halophilic
  organisms belonging to Archaea, Bacteria and some
  algae
• 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 KCl- to balance high
  external NaCl-
• A number of halophiles have a unique type of
  photosynthesis
• Multiple light-sensitive proteins
• Halorhodopsin (Cl- transport, creating Cl-
  gradient which drives K uptake)
• Bacteriorhodopsin (photosynthesis?)

Salt evaporation ponds
Great Salt Lake
28
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
• In high salt, will alter photosynthetic pathway
  to produce glycerol (water-soluble, nonionic
  substance which prevents dehydration) instead of
  starch

Dunaliella salina
29
Halobacterium salinarum and Light-mediated ATP
Synthesis
Halobacterium salinarum

• Halobacterium contain photopigments which are
  used to synthesize ATP as a result of proton
  motive force generation

30
Retinal chromophore of bacteriorhodopsin
trans-form
light
cis-form
31
High Salt Alkaline Environments Soda Lakes

• Have very high pH (gt 9) due to high levels of
  CO32- ion
• Very few organisms can tolerate alkaline
  conditions (to date only alkalophilic prokaryotes
  have been isolated)
• 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

Lake Magadi (Soda lake in Kenya)
Cyanobacterium Spirilina
Natronobacterium
32
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

33
DNA Damage Repair in Deinococcus radiodurans

• Deinococcus radiodurans has very efficient DNA
  repair machinery
• DNA sheared by radiation will reform within 24h

34
Importance of ExtremophilesExtremozymes

• 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

35
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 is postulated to have extremophilic regions
  including permafrost, hydrothermal vents, and
  evaporite crystals
• Europa is thought to have a subsurface ocean

Mars
Europa