Title: Extreme Biology
1 2Topics
- 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
3Universal Tree of Life 3 Domain System
Bacteria and Archaea are both prokaryotes
4Extreme Environments on Earth
- Sea Ice (extreme cold)
- Hydrothermal vents (extreme heat and high metal
content) - Sulfuric Springs (extreme heat and highly acidic)
- Salt Lake (extreme salt concentrations)
- Soda Lake (extreme salt concentration and highly
alkaline)
5Cellular Targets of Adaptations to Extreme
Environments
Typical Prokaryotic Cell
Cytoplasm water, proteins, metabolites, salts
Nucleoid Aggregated DNA Chromosome
Typically lipid bilayer
6Life 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
7Adaptations to Extreme Cold Making More Fluid
Membranes
More fluid membranes result from putting
unsaturated/polyunsaturated fatty acids into the
membrane
8More Life on Ice Algae
Algae living on the ice (photosynthetic
unicellular plant)
Lichen symbiotic relationship between algae and
fungi
Krill
Phytoplankton
9Polychaete Worms Living on Methane Ice
- It is thought that the worms eat the bacteria
that are growing on the methane ice
10Lake Vostoc A model for Life on Europa?
11Hydrothermal Vent Systems
12Anatomy of A Vent
13Hydrothermal 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
14Hydrothermal 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)
15Hydrothermal Vent Ecosystems The Prokaryotes
Bacteria
Archaea
Methanococcus janaschii (85C)
Vent contact slide
Aquifex aeolicus (95C)
Pyrococcus furiosus (100C)
Archaeoglobus fulgidus (83C)
Thermotoga maritima (90C)
16Thermal 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
17Hydrothermal 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).
18Endosymbiosis in Tubeworms
19Hydrothermal Vent Ecosystems Bivalves
Calyptogena magnifica
Bathymodiolus thermophilus
20Hydrothermal Vent Ecosystems Snow Flurries and
Crabs
Flocs of sulfur bacteria
Galatheid crabs
21And Where Theres Crabs, Octopi Are Not Far Behind
22 Continued
23Topics
- 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
24Extreme Environments on Earth
- Sea Ice (extreme cold)
- Hydrothermal vents (extreme heat and high metal
content) - Sulfuric Springs (extreme heat and highly acidic)
- Salt Lake (extreme salt concentrations)
- Soda Lake (extreme salt concentration and highly
alkaline)
25Life 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
26Other 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
27High 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
28Halophilic 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
29Halobacterium 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
30Retinal chromophore of bacteriorhodopsin
trans-form
light
cis-form
31High 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
32Survival 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
33DNA Damage Repair in Deinococcus radiodurans
- Deinococcus radiodurans has very efficient DNA
repair machinery - DNA sheared by radiation will reform within 24h
34Importance 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
35Importance 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