1. EXTREMOPHILES
NATURE’S ULTIMATE SURVIVORS

2. EXTREMOPHILES
I. What are they?
II. Types of Extremophiles
III. Extreme Prokaryotes
IV. Extreme Eukaryotes
V. Extreme Viruses
VI. Evolution of Extremophiles
VII. Biotechnological Uses
VIII. Industrial Uses
IX. Extraterrestrial Extremophiles?

3. What are Extremophiles?
Extremophiles are microorganisms— whether
viruses, prokaryotes, or eukaryotes— that
survive under harsh environmental conditions
that can include atypical temperature, pH,
salinity, pressure, nutrient, oxic, water, and
radiation levels

4. Types of Extremophiles
Types of Extremophiles

5. Types of Extremophiles
Other types include:
 Barophiles -survive under high pressure levels, especially
in deep sea vents
 Osmophiles –survive in high sugar environments
 Xerophiles -survive in hot deserts where water is scarce
 Anaerobes -survive in habitats lacking oxygen
 Microaerophiles -survive under low-oxygen conditions only
 Endoliths –dwell in rocks and caves
 Toxitolerants -organisms able to withstand high levels of
damaging agents. For example, living in water saturated
with benzene, or in the water-core of a nuclear reactor

6. Surviving the Extremes

7. EXTREME PROKARYOTES
Hyperthermophiles
-Members of
domains Bacteria
and Archaea
-Held by many
scientists to have
been the earliest
organisms
-Early earth was
excessively hot,
so these
organisms would
have been able to

8. Morphology of Hyperthermophiles
-Heat stable proteins that have more
hydrophobic interiors, which prevents
unfolding or denaturation at higher
temperatures
-Have chaperonin proteins that maintain
folding
-Monolayer membranes of dibiphytanyl
tetraethers, consisting of saturated fatty
acids which confer rigidity, preventing
them from being degraded in high
temperatures
-Have a variety of DNA-preserving substances
that reduce mutations and damage to
nucleic acids, such as reverse DNA gyrase The red on these rocks
and Sac7d is produced by
-They can live without sunlight or organic Sulfolobus solfataricus,
carbon as food, and instead survive on near Naples, Italy
sulfur, hydrogen, and other materials that
other organisms cannot metabolize

10. N acetyltalosaminuuronic acid

17. a | Schematic representation of a cross-section of the cell envelope of Sulfolobus solfataricus showing the cytoplasmic membrane, with
membrane-spanning tetraether lipids and an S-layer composed of two proteins — a surface-covering protein (red oval) and a membrane-
anchoring protein (yellow oblong). b | Schematic representation of a cell envelope of an archaeon that stains positive with the Gram stain
and that contains a pseudomurein layer in addition to the S-layer. The cytoplasmic membrane is composed of diether lipids.

24. Some Hyperthermophiles
Frequent habitats
include volcanic vents
and hot springs, as in
the image to the left
Pyrococcus abyssi 1µm Thermus aquaticus 1µm

25. Deep Sea Extremophiles
The deep-sea floor and hydrothermal
vents involve the following conditions:
low temperatures (2-3º C) – where only
psychrophiles are present
low nutrient levels – where only
oligotrophs present
high pressures – which increase at the
rate of 1 atm for every 10 meters in
depth (as we have learned, increased
pressure leads to decreased enzyme-
substrate binding)
barotolerant microorganisms live
at 1000-4000 meters
A black smoker, a submarine barophilic microorganisms live at
hot spring, which can reach depths greater than 4000 meters
518- 716°F (270-380°C)

26. Extremophiles of
Hydrothermal Vents
Natural
springs which
vent warm or
hot water on
the sea floor
near mid-
ocean ridges.
Associated
with the
spreading of
0.2µm 1µm the earth’s
A cross-section of a bacterium A bacterial crust. High
isolated from a vent. Often community from a temperatures
such bacteria are filled with deep-sea and pressures
viral particles which are hydrothermal vent
abundant in hydrothermal near the Azores
vents

27. Psychrophiles
Some microorganisms
thrive in temperatures
well below the
freezing point of
water, such as in
Some researchers believe that Antarctica
psychrophiles live in conditions mirroring
those found on Mars

28. Psychrophiles possess:
-proteins rich in α-helices and polar groups which allow for
greater flexibility
-“antifreeze proteins” that maintain liquid intracellular conditions
by lowering freezing points of other biomolecules
-membranes that are more fluid, containing unsaturated cis-fatty
acids which help to prevent freezing
-active transport at lower temperatures

29. Halophiles
-Divided into mild (1-6%NaCl), moderate (6-15%NaCl), and extreme
(15-30%NaCl)
-Halophiles are mostly obligate aerobic archaea
How do halophiles survive high salt concentrations?
-by interacting more strongly with water such as using more
negatively charged amino acids in key structures
-by making many small proteins inside the cell, and these, then,
compete for the water
-and by accumulating high levels of salt in the cell in order to
outweigh the salt outside

30. Barophiles
-Survive under levels
of pressure that are
otherwise lethal to
other organisms
-Usually found deep in
the earth, in the deep
sea, hydrothermal
vents, etc
1µm -scientists believe that
A sample of barophilic barophiles may be
bacteria from the able to survive on the
earth’s interior Moon and other places
in space

31. Xerophiles
Extremophiles which live in water-
scarce habitats, such as deserts
Produce desert varnish as seen
in the image to the left
Desert varnish is a thin coating of
Mn, Fe, and clay on the surface of
desert rocks, formed by colonies
of bacteria living on the rock
surface for thousands of years

32. SOME COMMON GENERA OF PROKARYOTE EXTREMOPHILES
2um 1.8um 1um
Thermotoga Aquifex Halobacterium
0.6um 0.9um 0.9um
Methanosarcina Thermoplasma Thermococcus
1.3um 0.6um
0.7um
Thermoproteus Pyrodictium Ignicoccus

33. Deinococcus radiodurans
The Radiation Resistor
-Possesses extreme resistance to
up to 4 million rad of radiation,
genotoxic chemicals (those that
harm DNA), oxidative damage from
peroxides/superoxides, high levels
of ionizing and ultraviolet
radiation, and dehydration
-It has from four to ten DNA
molecules compared to only one
for most other bacteria
0.8µm
-Contains many DNA repair enzymes, such as RecA, which
matches the shattered pieces of DNA and splices them back
together. During these repairs, cell-building activities are shut off
and the broken DNA pieces are kept in place

34. Chroococcidiopsis
The Cosmopolitan Extremophile
1.5µm
-A cyanobacteria which can survive in a variety of harsh
environments, such as hot springs, hypersaline habitats, hot,
arid deserts throughout the world, and in the frigid Ross
Desert in Antarctica
-Possesses a variety of enzymes which assist in such
adaptation

35. Other Prokaryotic Extremophiles
1µm 1µm
Gallionella ferrugineaand Anaerobic bacteria
(iron bacteria), from a cave
Current efforts in microbial taxonomy are isolating more and
more previously undiscovered extremophile species, in places
where life was least expected

36. EXTREME EUKARYOTES
THERMOPHILES/ACIDOPHILES
2µm

37. EXTREME EUKARYOTES
PSYCHROPHILES
2µm
Snow Algae (Chlamydomonas nivalis) A bloom of Chloromonas
rubroleosa in Antarctica
These algae have successfully adapted to their harsh
environment through the development of a number of
adaptive features which include pigments to protect against
high light, polyols (sugar alcohols, e.g. glycerine), sugars
and lipids (oils), mucilage sheaths, motile stages and spore

38. EXTREME EUKARYOTES
ENDOLITHS
Quartzite from Johnson
Canyon, California.
Sample shows green
bands of endolithic
algae. Rock is 9.5 cm
wide
-Endoliths (also called hypoliths) are usually
algae, but can also be prokaryotic cyanobacteria,
that exist within rocks and caves
-Often are exposed to anoxic (no oxygen) and
anhydric (no water) environments

39. EXTREME EUKARYOTES
PARASITES
-Members of the Phylum Protozoa, which are
regarded as the earliest eukaryotes to evolve, are
mostly parasites
-Parasitism is often a stressful relationship on both
host and parasite, so they are considered
extremophiles
20µm
15µm
Trypanosoma gambiense, Balantidium coli, causes
causes African sleeping dysentery-like symptoms
sickness

40. EXTREME VIRUSES
Viruses are currently being
isolated from habitats where
temperatures exceed 200°F
Instead of the usual
icosahedral or rod-shaped
capsids that known viruses
possess, researchers have
40nm
found viruses with novel
Virus-like particles propeller-like structures
isolated from the extreme
environment of
Yellowstone National Park These extreme viruses often
hot springs live in hyperthermophile
prokaryotes such as
Sulfolobus

41. CLASSIFICATION OF EXTREMOPHILES
Phylogenetic Relationships
Extremophiles are present among Bacteria, form
the majority of Archaea, and also a few among the
Eukarya

42. PHYLOGENETIC RELATIONSHIPS
-Members of Domain Bacteria (such as Aquifex and
Thermotoga) that are closer to the root of the
“tree of life” tend to be hyperthermophilic
extremophiles
-The Domain Archaea contain a multitude of
extremophilic species:
Phylum Euryarchaeota-consists of methanogens
and extreme halophiles
Phylum Crenarchaeota-consists of
thermoacidophiles, which are extremophiles that
live in hot, sulfur-rich, and acidic solfatara
springs
Phylum Korarchaeota-new phylum of yet
uncultured archaea near the root of the Archaea
branch, all are hyperthermophiles
-Most extremophilic members of the Domain
Eukarya are red and green algae

43. Chronology of Life

44. The First Organisms?
Early Earth was largely inhospitable: high CO 2/H2S/H2
etc, low oxygen, and high temperatures
Lifeforms that could evolve in such an environment
needed to adapt to these extreme conditions
H2 was present in abundance in the early
atmosphere. Many hyperthermophiles and
archaea are H2 oxidizers
Thus, it is widely held that extremophiles represent
the earliest forms of life with non-extreme forms
evolving after cyanobacteria had accumulated
enough O2 in the atmosphere
Results of rRNA and other molecular techniques
have placed hyperthermophilic bacteria and
archaea at the roots of the phylogenetic tree of
life

45. Evolutionary Theories
 Consortia- symbiotic relationships between microorganisms,
allows more than one species to exist in extreme habitats
because one species provides nutrients to the others and vice
versa
 Genetic drift appears to have played a major role in how
extremophiles evolved, with allele frequencies randomly
changing in a microbial population. So alleles that conferred
adaptation to harsh habitats increased in the population, giving
rise to extremophile populations
 Geographic isolation may also be a significant factor in
extremophile evolution. Microorganisms that became isolated in
more extreme areas may have evolved biochemical and
morphological characteristics which enhanced survival as
opposed to their relatives in more temperate areas. This
involves genetic drift as well

46. Slower Evolution
-Extremophiles, especially hyperthermophiles,
possess slow “evolutionary clocks”
-That is, they have not evolved much from their
ancestors as compared to other organisms
-Hence, hyperthermophiles today are similar to
hyperthermophiles of over 3 billion years ago
-Slower evolution may be the direct result of living
in extreme habitats and little competition
-By contrast, other extremophiles, such as extreme
halophiles and psychrophiles, appear to have
undergone faster modes of evolution since they
live in more specialized habitats that are not
representative of early earth conditions

47. Mat Consortia
Mat Consortia
A mat
consortia in
Yellowstone
-Microbial mats consist of an upper layer of photosynthetic
bacteria, with a lower layer of nonphotosynthetic bacteria
-These consortia may explain some of the evolution that has
taken place: extremophiles may have relied on other
extremophiles and non-extremophiles for nutrients and shelter
-Hence, evolution could have been cooperative

48. USES OF EXTREMOPHILES
HYPERTHERMOPHILES (SOURCE) USES
DNA polymerases DNA amplification by PCR
Alkaline phosphatase Diagnostics
Proteases and lipases Dairy products
Lipases, pullulanases and proteases Detergents
Proteases Baking and brewing and amino
acid production from keratin
Amylases, α-glucosidase, pullulanase and xylose/glucose isomerases
Baking and brewing and amino
acid production from keratin
Alcohol dehydrogenase Chemical synthesis
Xylanases Paper bleaching
Lenthionin Pharmaceutical
S-layer proteins and lipids Molecular sieves
Oil degrading microorganisms Surfactants for oil recovery
Sulfur oxidizing microorganisms Bioleaching, coal & waste gas
desulfurization
Hyperthermophilic consortia Waste treatment and methane
production

49. USES OF EXTREMOPHILES
PSYCHROPHILES (SOURCE) USES
Alkaline phosphatase Molecular biology
Proteases, lipases, cellulases and amylases
Detergents
Lipases and proteases Cheese manufacture and dairy
production
Proteases Contact-lens cleaning solutions,
meat tenderizing
Polyunsaturated fatty acids Food additives, dietary
supplements
Various enzymes Modifying flavors
b-galactosidase Lactose hydrolysis in milk
products
Ice nucleating proteins Artificial snow, ice cream, other
freezing applications in the food
industry
Ice minus microorganisms Frost protectants for
sensitive plants
Various enzymes (e.g. dehydrogenases)
Biotransformations
Various enzymes (e.g. oxidases)Bioremediation, environmental
biosensors
Methanogens Methane production

50. USES OF EXTREMOPHILES
HALOPHILES (SOURCE) USES
Bacteriorhodopsin Optical switches and photocurrent generators in
bioelectronics
Polyhydroxyalkanoates Medical plastics
Rheological polymers Oil recovery
Eukaryotic homologues (e.g. myc oncogene product)
Cancer detection, screening anti-tumor drugs
Lipids Liposomes for drug delivery and cosmetic
packaging
Lipids Heating oil
Compatible solutes Protein and cell protectants in variety of
industrial uses, e.g. freezing, heating
Various enzymes, e.g. nucleases, amylases, proteases
Various industrial uses, e.g. flavoring agents
g-linoleic acid, b-carotene and cell extracts, e.g. Spirulina and Dunaliella
Health foods, dietary supplements, food coloring
and feedstock
Microorganisms Fermenting fish sauces and modifying food
textures and flavors
Microorganisms Waste transformation and degradation, e.g.
hypersaline waste brines contaminated with a
wide range of organics
Membranes Surfactants for pharmaceuticals

51. USES OF EXTREMOPHILES
ALKALIPHILES (SOURCE) USES
Proteases, cellulases, xylanases, lipases and pullulanases
Detergents
Proteases Gelatin removal on X-ray
film
Elastases, keritinases Hide dehairing
Cyclodextrins Foodstuffs, chemicals and
pharmaceuticals
Xylanases and proteases Pulp bleaching
Pectinases Fine papers, waste
treatment and degumming
Alkaliphilic halophiles Oil recovery
Various microorganisms Antibiotics
ACIDOPHILES (SOURCE) USES
Sulfur oxidizing microorganisms Recovery of metals and
desulfurication of coal
Microorganisms Organic acids and solvents

52. Taq Polymerase
Isolated from the
hyperthermophile
Thermus aquaticus
Much more heat stable
Used as the DNA
polymerase in the very
useful Polymerase
Chain Reaction (PCR)
technique which
amplifies DNA samples

53. Alcohol Dehydrogenase
-Alcohol dehydrogenase (ADH), is
derived from a member of the archaea
called Sulfolobus solfataricus
-It works under some of nature's
harshest volcanic conditions: It can
survive to 88°C (190ºF) - nearly boiling
- and corrosive acid conditions
(pH=3.5) approaching the sulfuric acid
found in a car battery (pH=2)
-ADH catalyzes the conversion of
alcohols and has considerable
potential for biotechnology
applications due to its stability under
these extreme conditions

54. Bacteriorhodopsin
-Bacteriorhodopsin is a
trans-membrane protein
found in the cellular
membrane of
Halobacterium
salinarium, which
functions as a light-
driven proton pump
-Can be used for
electrical generation

55. Bioremediation
- Bioremediation is the branch of biotechnology
that uses biological processes to overcome
environmental problems
- Bioremediation is often used to degrade
xenobiotics introduced into the environment
through human error or negligence
- Part of the cleanup effort after the 1989
Exxon Valdez oil spill included
microorganisms induced to grow via nitrogen
enrichment of the contaminated soil

56. Bioremediation

57. Psychrophiles as Bioremediators
- Bioremediation applications with cold-
adapted enzymes are being considered for
the degradation of diesel oil and
polychlorinated biphenyls (PCBs)
- Health effects that have been associated with
exposure to PCBs include acne-like skin
conditions in adults and neurobehavioral and
immunological changes in children. PCBs are
known to cause cancer in animals

58. An End to Pollution?
New and innovative methods are being
developed that utilize extremophiles for the
elimination of pollution resulting from oil
slicks, toxic chemical spills, derelict mines,
etc

59. Life in Outer Space?
-Scientists have decided on 3 requirements for life:
water
energy
carbon
-Astrobiology: field of biology dealing with the existence of life
beyond earth
-Astrobiologists are currently looking for life on Mars,
Jupiter’s moon Europa, and Saturn’s moon Titan
-Such life is believed to consist of extremophiles that can
withstand the cold and pressure differences
-Mudslide-like formations have been
found on Mars (left). These appear to
have been caused by water
movements. Psychrophiles may exist
there

60. Life in Outer Space?
-Europa is thought to have an ice
crust shielding a 30-mile deep
ocean. Reddish cracks (left) are
visible in the ice and may be
evidence of living populations
-Titan is enveloped with a hazy
gas (left) that is believed to
contain some organic
molecules, ie methane. This
may provide sustenance for life
on Titan’s surface
Images courtesy of the Current Science & Technology Center

61. Life in Outer Space?
-Scientists have found that
meteorites contain amino
acids and simple sugars,
very important building
blocks. These may serve
to spread life throughout
the universe
Image courtesy of the Current Science & Technology Center
-A sample of stratospheric
air had shown a myriad of
bacterial diversity 41 km
above the earth’s surface
(Lloyd, Harris, & Narlikar,
2001)
Indeed, we may not be alone

62. A. The archaea are quite diverse, both in morphology and
physiology
1. They may stain gram positive or gram negative
2. They may be spherical, rod-shaped, spiral, lobed,
plate-shaped, irregularly shaped or pleomorphic
3. They may exist as single cells, aggregates or filaments
4. They may multiply by binary fission, budding,
fragmentation, or other mechanisms
5. They may be aerobic, facultatively anaerobic, or
strictly anaerobic
6. Nutritionally, they range from chemilithoautotrophs to
organotrophs
7. Some are mesophiles, while others are
hyperthermophiles that can grow above 100°C
8. They are often found in extreme aquatic and terrestrial
habitats; recently, archaea have been found in cold
environments and may constitute up to 34% of the
procaryotic biomass in Antarctic surface waters; a few
are symbionts in animal digestive systems

63. Archaeal cell walls
1. Archaea can stain either gram positive or gram negative,
but their cell wall structure differs significantly from that of
bacteria
a. Many archaea that stain gram positive have a cell wall
made of a single homogeneous layer
b. The archaea that stain gram negative lack the outer
membrane and complex peptidoglycan network
associated with gram-negative bacteria
2. Archaeal cell wall chemistry is different from that of
bacteria
a. Lacks muramic acid and D-amino acids and therefore
is resistant to lysozyme and b-lactam antibiotics
b. Some have pseudomurein, a peptidoglycan-like
polymer that has L-amino acids in its cross-links and
different monosaccharide subunits and linkage
c. Others have different polysaccharides
3. The archaea that stain gram negative have a layer of protein
or glycoprotein outside their plasma membrane

64. Archaeal lipids and membranes
1. Lipids have branched hydrocarbons attached to glycerol by
ether links rather than straight-chain fatty acids attached to
glycerol by ester links as seen in Bacteria and Eucarya
2. Other, more complex tetraether structures are also found
3. Membranes contain polar lipids such as phospholipids,
sulfolipids, and glycolipids and also contain nonpolar lipids
(7-30%), which are usually derivatives of squalene
4. Membranes of extreme thermophiles are almost completely
tetraether monolayers

65. F. • Archaeal Taxonomy-the new edition of Bergey’s Manual
will divide the archaea into two phyla: Euryarchaeota and
Crenarchaeota
• Phylum Crenarchaeota
A. Many are extremely thermophilic, acidophilic, and sulfur-
dependent
1. Sulfur may be used as an electron acceptor in
anaerobic respiration, or as an electron source by
lithotrophs
2. Almost all are strict anaerobes
3. They grow in geothermally heated water or soils
(solfatara) that contain elemental sulfur (sulfur-rich
hot springs, waters surrounding submarine volcanic
activity); some (e.g., Pyrodictum spp.) can grow quite
well above the boiling point of water (optimum @
105oC)
4. Some are organotrophic; others are lithotrophic
5. There are 69 genera; two of the better-studied genera
are Sulfolobus and Thermoproteus

66. A. Sulfolobus
1. Stain gram negative; are aerobic, irregularly lobed,
spherical bacteria
2. Thermoacidophiles
3. Cell walls lack peptidoglycan but contain lipoproteins
and carbohydrates
4. Oxidize sulfur to sulfuric acid; oxygen is the normal
electron acceptor, but ferric iron can also be used
5. Sugars and amino acids may serve as carbon and
energy sources

67. A. Thermoproteus
1. Long, thin, bent or branched rods
2. Cell wall is composed of glycoprotein
3. Strict anaerobes
4. They have temperature optima from 70-97°C and pH
optima from 2.5 to 6.5
5. They grow in hot springs and other hot aquatic
habitats that contain elemental sulfur
6. They carry out anaerobic respiration using organic
molecules as electron donors and elemental sulfur as
the electron acceptor; they can also grow
lithotrophically using H2 and S0 as electron donors
and CO or CO2 as the sole carbon source

68. • Phylum Euryarchaeota
A. The Methanogens
1. Strict anaerobes that obtain energy by converting CO2,
H2, formate, methanol, acetate, and other compounds
to either methane or to methane and CO2; there are at
least five orders, which differ greatly in shape, 16S
rRNA sequence, cell wall chemistry and structure,
membrane lipids, and other features
2. Methanogens belonging to the order Methanopyrales
have been suggested to be among the earliest
organisms to evolve on Earth
3. Methanogenesis is an unusual metabolic process and
methanogens contain several unique cofactors
4. They thrive in anaerobic environments rich in organic
matter, such as animal rumens and intestinal tracts,
freshwater and marine sediments, swamps, marshes,
hot springs, anaerobic sludge digesters, and even
within anaerobic protozoa
5. They are of great potential importance because
methane is a clean-burning fuel and an excellent
energy source
6. They may be an ecological problem, however, because
methane is a greenhouse gas that could contribute to
global warming and also because methanogens can
oxidize iron, which contributes significantly to the
corrosion of iron pipes

69. A. The Halobacteria
1. A group of extremely halophilic organisms divided
into 15 genera
a. They are aerobic chemoheterotrophs with
respiratory metabolism; they require complex
nutrients
b. Motile or nonmotile by lophotrichous flagella
2. They require at least 1.5 M NaCl and have growth
optima near 3-4 M NaCl (if the NaCl concentration
drops below 1.5 M the cell walls disintegrate; because
of this they are found in high-salinity habitats and can
cause spoilage of salted foods
3. Halobacterium salinarum uses four different light-
utilizing rhodopsin molecules
a. Bacteriorhodopsin uses light energy to drive
outward proton transport for ATP synthesis; thus
they carry out a type of photosynthesis that does
not involve chlorophyll
b. Halorhodopsin uses light energy to transport
chloride ions into the cell to maintain a 4-5 M
intracellular KCl concentration
c. Two other rhodopsins act as photoreceptors that
control flagellar activity to position the bacterium
in the water column at a location of high light
intensity, but one in which the UV light is not
sufficiently intense to be lethal

70. A. The Thermoplasms
0. Thermoacidic organisms that lack cell walls; only two
genera are know: Thermoplasma and Picrophilus
1. Thermoplasma
a. Frequently found in coal mine refuse, in which
chemolithotrophic bacteria oxidize iron pyrite to
sulfuric acid and thereby produce a hot acidic
environment
b. Optimum temperature for growth of 55-59°C and
an optimal PH of 1 to 2
c. Cell membrane is strengthened by large
quantities of diglycerol tetraethers,
lipopolysaccharides, and glycoproteins
d. Histonelike proteins stabilize their DNA; DNA-
protein complex forms particles resembling
eucaryotic nucleosomes
e. At 59oC Thermoplasma takes the form of an
irregular filament; the cells may be flagellated
and motile

71. 1. Picrophilus
a. Isolated from hot solfateric fields
b. Has an S-layer outside the plasma membrane
c. Irregularly shaped cocci with large cytoplasmic
cavities that are not membrane bounded
d. Aerobic and grows between 47°C and 65°C with
an optimum of 60°C
e. It grows only below pH 3.5, has an optimum of
pH 0.7 and will even grow at or near pH 0

72. A. Extremely thermophilic S0 metabolizers
0. Strictly anaerobic, reduce sulfur to sulfide
1. Are motile by means of flagella
2. Have optimum growth temperatures around 88-100°C
B. Sulfate-reducing archaea
0. Gram-negative, irregular coccoid cells with walls of
glycoprotein subunits
1. Use a variety of electron donors (hydrogen, lactate,
glucose) and reduce sulfite, sulfate, or thiosulfate to
sulfide
2. Are extremely thermophilic (optimum around 83°C);
they are usually found near marine hydrothermal vents
3. Contain two methanogen coenzymes

73. CONCLUSIONS
-Extremophiles are a very important and integral
part of the earth’s biodiversity
They:
- reveal much about the earth’s history and
origins of life
- possess amazing capabilities to survive in the
extremes
- are proving to be beneficial to both humans and
the environment
-may exist beyond earth