Extremophiles are organisms that thrive in extreme environmental conditions such as high temperatures, high salt concentrations, low or high pH, and radiation. They include bacteria, archaea, and eukaryotes found in hot springs, deep sea hydrothermal vents, salt lakes, and deserts. Extremophiles have adapted mechanisms to withstand these conditions such as membrane modifications, molecular chaperones, and DNA repair enzymes. They have applications in biotechnology including DNA polymerases for PCR, biofuel production, biomining, production of industrial enzymes and pigments.

1. EXTREMOPHILES AND THEIR SIGNIFICANCE
Course No. AEM-504
Presented By-
Sakshi
AEM-MA-09-06

2. Introduction
• An extremophile (from Latin extremus -"extreme" and philiā - "love") is an organism
with optimal growth in environmental conditions considered extreme ( Physical &
Chemical).
• RD MacElroy first coined the term “extremophile” in a 1974.
• Extremophiles are organisms that live and thrive in habitats where life is impossible
for most living organisms.
• Extremophiles have the ability to withstand conditions such as high radiation, high
or low pressure, high or low pH, lack of light, extreme heat, extreme cold and
extreme dryness.

3. contd...
• Extremophiles include members of all three domains of life, i.e., bacteria, archaea
(high proportion) and eukarya. This group also includes eukaryotes such as protists
(e.g., algae, fungi and protozoa) and multicellular organisms.
• Some organisms occupy more than one environmental extreme simultaneously, and
are known as polyextremophiles.
An example is the archaebacterial species, Sulfolobus acidocalderius which
thrives in boiling mudpots at temperatures exceeding 800C and at acidities less than
pH 3.

4. contd...
Extremophiles may be divided into two broad categories:
Extremophilic organisms
Extremophilic organisms which require
one or more extreme conditions in order
to grow.
Extremotolerant organisms
Extremotolerant organisms which can
tolerate extreme values of one or more
physicochemical parameters though
growing optimally at “normal” conditions.

5. Physical Extremes
• Temperature
For high temperatures, this environment includes geysers and hot springs, boiling
mudpots, and hydrothermal vents on the deep seafloor. Thermophilic species exhibit
growth up to a temperature of about 1140C .
• Pressure
Pressure, which is measured relative to atmospheric pressure at sea level increases
with depth in the oceans. In the ocean, this hydrostatic pressure goes up at the rate of
approximately 1 bar per 100 meters.
• Radiation
Radiation is energy that travels as either particles (e.g., high energy neutrons, protons,
electrons, or ions) or waves (e.g., X-rays, gamma rays, or UV rays). e.g., Deinococcus
radiodurens.

6. Chemical Extremes
• pH
Chemical extremes in the environment include pH, which ranges from values of less
than 0 (extremely acidic) to more than 14 (extremely alkaline or basic). In nature,
microorganisms have been shown to occupy nearly the entire range of pH.
• Salinity
Salt-loving halophiles live in salt plains, evaporation ponds at saltworks, and natural
salt lakes (e.g., the Dead Sea, Israel and the Great Salt Lake). In nature, salinities can
range from fresh water, with very low salinity, to super-saturated brines.
• Desiccation
The ability to survive desiccation (extreme drying) has been demonstrated for both
vegetative cells and reproductive spores of many microbial species. In the driest
deserts on Earth, microbial species (so-called "endoliths") often survive by living inside
porous rocks where they are protected from ultraviolet radiation.

7. Different classes of extremophiles
• Thermophile: An organism that thrives in environments with high temperature;
between 45-700C.
• Hyperthermophile: An organism that thrives in environments with extremely high
temperatures; between 80–1220C.
• Acidophile: An organism that thrives in acidic environments with pH levels of 3 and
below.
• Alkaliphile: An organism that thrives in alkaline environments with pH levels of 9
and above.
• Halophile: An organism that lives in habitats with extremely high salt
concentrations.

8. contd...
• Barophile: An organism that lives in high pressure environments, such as
deep-sea habitats.
• Osmophiles: An organism thatsurvive in high sugar environment.
• Psychrophile: An organism that survives in extreme cold conditions and low
temperatures; between −200C to +100C.
• Radiophile: An organism that thrives in conditions with high levels of
radiation, including ultraviolet and nuclear radiation.
• Xerophile: An organism that lives in extreme dry conditions.

9. Thermophiles
• Microorganisms able to grow optimally at temperatures above 400C are referred as
thermophile.
• Habitats including hot springs, geothermal locations, composts and sun heated
soil.
• Grow optimally at temperatures between 50-700C, they can also grow, though
slowly, at below 400C.
• Belong to various taxonomic groups, such as bacteria, actinomycetes, fungi,
protozoa, algae and blue green bacteria.
• Eubacteria and archaeabacteria able to grow at temperatures between 80 and
1100C.
Examples: Thermos aquaticus , Geobacillus spp. etc.

10. Mesophiles
• Organisms categorized as mesophiles (“middle loving”) are adapted to
moderate temperatures, with optimal growth temperatures ranging from
room temperature (about 200C) to about 450C.
Examples: E. coli, Salmonella spp., and Lactobacillus spp etc.

11. Hyperthermophiles
• Organisms, which were unable to grow
below 600C.
• Microbes isolated from the vents achieve
optimal growth at temperatures higher
than 1000C.
• Examples are Pyrobolus and Pyrodictium,
archaea that grow at 1050C.

12. contd..

13. Habitats
Fresh water alkaline hot springs
• Located outside volcanically active zones
• The pH ranges from 9-10 and the temperature is around 750C.
• Thermothrix thiopara, methanobacterium thremoautotrophicum and
desulfovibrio thermophilus are the autotrophs which can grow up to 80-850C,
the optimum temperature and pH being 65-750C and 6.8-7.5.
Geysers
• Geysers are a rare and special class of boiling spring.
• They occur when underground water cannot discharge freely, but is forced
through a narrow neck or opening from a larger reservoir below.

14. contd...
Acidic solfatara fields
• The geothermal areas are dominated by solfatara fields containing large
amount of sulfur.
• Both autotrophs (Sulfolobus acidocaldarius and Acidianus infernos) and
heterotrophs (Thermoplasm volcanium and Sulfolobus acidocaldarius) groups
can grow optimally at pH 2-2.5 and temperatures 60-900C.
• These chemolithotrophic acidophiles often are the predominant primary
producers and may also contribute to iron and sulfur cycling via oxidization of
reduced inorganic sulfur compounds .

15. Adaptive mechanisms
• They contain ether lipids derived from diphytanyl-glycerol, which exhibit a
remarkable resistance against hydrolysis at high temperatures and an acidic pH.
• Thermal resistance of the DNA double helix appears to be improved in
hyperthermophiles by reverse gyrase, a unique type I DNA topoisomerase that
causes positive supertwists for stabilization.
• Archaeal hyperthermophiles possess histones. It increases melting temperature
drastically.
• Heat-shock proteins prevents unfolding or denaturtion at higher temperatures.
• Chaperonin that maintain folding.

16. Psychrophiles
• Psychrophiles or cryophiles are extremophilic organisms that are capable
of growth and reproduction in low temperatures, ranging from −200C to
+100C.
• They often found in other extremely cold environments such as deep oceans,
caves, permafrost (frozen soils), glaciers and ice sheets,land surfaces and even
in the upper atmosphere.
Psychrophiles may be divided into two broad categories:
1. Stenopsychrophiles (formerly true psychrophiles) have an upper temperature
limit of 200C for growth.
2. Eurypsychrophile (formerly psychrotolerant) and have a broader temperature
range, tolerating warmer environments.

17. contd...
• Psychrotrophs, also known as psychrotolerant, prefer cooler environments,
from a high temperature of 250C to refrigeration temperature about 40C. They
are found in many natural environments in temperate climates. They are also
responsible for the spoilage of refrigerated food.
• They are active at low temperature, psychrophiles and psychrotrophs are
important decomposers in cold climates.
Examples: Arthrobacter ,Colwellia,Pseudomona, Halobacillus
Pseudoalteromonas etc.

18. Adaptive mechanisms
• Cold shock proteins (CSPs) and cold acclimation proteins act as cold-adaptive
proteins in psychrophiles. They are small proteins that bind to RNA to
preserve its single-stranded conformation and contain a nucleicacid- binding
domain.
• Higher proportion of unsaturated fatty acids (52%) compared to mesophilic
(37%) and thermophilic (10%) organisms, favoring the maintenance of the
semi-fluid state of membranes.
• Cold-active enzymes, include protein-tyrosine phosphatase , α-amylase and
β-galactosidase and aminopeptidase.
• Antifreeze proteins (AFPs) in preventing freezing of blood of fishes in low-
temperature environment.

19. Halophiles
• Halophiles are microorganisms that require salt (NaCl) for growth, and they
can be found in lakes, oceans, salt pans or salt marshes
Classified in three categories:
1. Extreme halophile-Grows in an environment having (20% to 30%) NaCl
2. Moderate halophile-Grows in an environment having (3% to 25%) NaCl
3. Slightly halophile-Grows in an environment having (1% to 5%) NaCl .
Examples: Halobacterium ,Haloferax volcanii , Fabrea salina, Desulfovibrio
halophilus , Chloroflexus aurautiacus etc.

20. Adaptive mechanisms
1. “High salt-in” strategy
• accumulate inorganic ions (K, Na , Cl ) in the cytoplasm.
• Maintains osmosis and prevents movement of water in and out of the cell.
2. “Low-salt, compatible organic-solutes-in” strategy
• specific organic osmolytes: Osmoprotectants.
• sugar, polyols, amino acids etc.
• Regulates osmosis.
3. Negative surface charges
• solvation of halophilic proteins, to prevent denaturation, aggregation and
precipitation.

21. Piezophiles/ Barophiles
• Piezophilic: Microorganisms which possess optimal growth rates at pressures
above atmospheric pressure.
• Piezotolerant: those that grow at high pressure, as well as at atmospheric
pressure but they do not have optimal growth rates at pressures above one.
Classified in three categories:
• Barotolerants (facultative): Grows at pressure from 100-400 Atm.
• Barophilic (obligative): Grows at pressure greater than 400 Atm.
• Extreme Barophilic: Grows at pressures higher than 700 Atm.

22. contd...
• Mariana Trench has a maximum depth of 11 km and a pressure of
1100 atm (110 MPa) harbors Moritella yayanosii and Shewanella
benthica.
Example : Photobacterium, Shewanella, Colwellia, Psychromonas,
Moritella etc.

23. Adaptive mechanism
• Lipids with highly unsaturated fatty acids.
• Reduction of cell division, modification of membrane and transport proteins
and accumulation of osmolytes, which stabilize the proteins.
• The occurrence of elongated helices in the 16S rRNA genes to increase
adaptation to growth at elevated pressure.

24. Acidophiles
• Organisms which survives in highly acidic conditions.
• Optimal growth at pH levels of 3 or below.
• Fungi as a group tend to be more acid tolerant than bacteria. Many fungi
grow optimally at pH 5 or below and a few grow well at pH value as low as 2.
Examples : Thiobacillus spp., Sulfolobus , Thermoplasma, Hydrogenobaculum
acidophilum, Alicyclobacillus acidocaldarius etc.

25. Adaptive mechanisms
• They survive by keeping the acid out. Since, they cannot tolerate great acidity
inside their cells, where it would destroy DNA.
• Acidophiles maintain the cytoplasmic pH around 6.5
• Rigid and impermeable cell membrane, which can restrict the cytoplasmic
influx of protons.

26. Alkaliphiles
• Live in soils laden with carbonate and in soda lakes, such as those found in
the india (Maharashtra), rift valley of africa and the west U.S.
• Optimal growth at pH levels of 9 or above.
Classified as:
• Alkali-tolerant organisms: (ph 7.0-9.0) (which cannot grow above ph 9.5)
• Alkalophilic organisms (ph 10.0-12.0).
Example: Bacillus alkalophilus, B.firmus, Bacillus subtilis, Natronomonas
pharaonis etc.

27. Adaptive mechanisms
• Cytoplasm rich in amino acids with positively charged side groups (lysine,
arginine, and histidine) or by low membrane permeability.
• Presence pH stable enzymes.
• Cell wall contain certain acidic polymers, such as galacturonic acid, gluconic
acid, glutamic acid, aspartic acid, and phosphoric acid in addition to
peptidoglycan.

28. Xerophiles
• Xerophiles are the organisms that can grow and reproduce in conditions with
a low availability of water, also known as water activity i.e,which live in water
scarce habitats, such as deserts.
• They can survive in the environment with water activity below 0.8.
• Water activity (aw) is a measure of the amount of water within a substrate that
an organisms can cause to support sexual growth.
• Endoliths and halophiles are often xerotolerant.
• Many molds and yeast species are Xerophiles. Mold growth on bread is an
example of food spoilage by Xerophilic organisms.
Example: Trichosporonoides nigrescens , Tardigrades etc.

29. Radioresistor
• Radioresistor are the organisms resistant to high levels of ionizing radiation,
upto 4 million rad of radiations.
• Most commonly UV radiation.
• DNA is the critical target to radiation.
• Damage is largely owing to an inhibition of cell replication due to affected
DNA.
Example: Thermococcus gammatolerans, Micrococcus radiodurans,Deinococcus
radiodurans etc.

30. Adaptive mechanisms
• Radiation resistant organisms often tends to be highly pigmented.
Pigmentation act as an energy sink, preventing the effect if visible light from
damaging the DNA.
• Cell wall structure less permeable to different radiation wavelengths.
• Under aquatic environments, organisms may adapt circadium rhythms,
avoiding the bulk of radiation.
• They contains the DNA repair enzymes, such as RecA,which matches the
shattered pieces of DNA and splices them back together.

31. Significance of Extremophiles
1.DNA polymerases: from the thermophiles Thermus aquaticus, Pyrococcus
furiosus, and Thermococcus litoralis, otherwise known as Taq , Pfu , and Vent :
PCR.
2.Biofuel production: larger-scale microorganism-based systems using the
thermophiles like-
• Methanogens : methane
• Thermoanaerobacterium saccharolyticum: ethanol
• Clostridium: butanol
• Extremophilic algae (e.g. Cyanidium caldarium and Galdieria sulphuraria:
biodiesel

32. contd...
3.Biomining: bioleaching, is the removal of insoluble metal sulfides or oxides by
using microorganisms.
• Acidophiles such as Acidithiobacillus and Ferroplasma
• thermophilic strains, like Sulfolobus and Metallosphaera
4. Carotenoids:
• Bacteriorhodopsin: membrane-bound retinal pigment, Halobacterium
salinarum.
• Canthaxanthin: lipid-soluble antioxidant used as a food dye and a feed additive,
Haloferax alexandrinus.
• β-carotene: red/orange pigment, halophilic alga Dunaliella salina is the major
source for β-carotene.

33. contd...
5.Proteases/lipases:
• Proteases; largest application is in laundry detergents, cheese making, brewing,
and baking.
• e.g.,.Bacillus sp.
• Lipases; Bacillus and Aspergillus species
6.Glycosyl hydrolases and sugars
• Glycosyl hydrolases hydrolyze the glycosidic bond between a carbohydrate and
another moiety.
• lactose-free milk and other dairy products, which are generated via the use of
the lactase (β-galactosidase) from organisms like Kluyveromyces lactis.

34. contd...
• production of carbohydrates like trehalose and ectoine, which can be used as
stabilizers for products like antibodies and vaccines.
• Sulfolobus solfataricus for production of trehalose.
• Radioresistor can be tapped to remediate radioactive materials from the
environment.
7. Bioremediators
• Most psychrophiles are used for the degradation of diesel oil and
polychlorinated biphenyls.
• It is often used to degrade xenobiotics introduced into the environment
through human error or negligence.

35. contd...
8.Medical applications
• Generate antimicrobial peptides and diketopiperazines.
• Antimicrobial peptides have been found in the Halobacteriaceae
(phylogenetic family containing all halophilic archaea) as well as Sulfolobus
species.
• Diketopiperazines (also known as cyclic dipeptides) affect blood-clotting
functions as well as having antimicrobial, antifungal, antiviral, and antitumor
properties. found in halophiles like Naloterrigena hispanica and
Natronococcus occultus .
• extremophiles produce polyhydroxyalkanoates (PHAs), which are a
heterogeneous group of polyesters. PHAs are often used as carbon storage
for microbial cells but have been harnessed to generate bioplastics.

36. Extremozymes and their uses

37. Reference
• Cockell, Charles S, et al. "Exposure of Phototrophs to 548 Days in Low Earth Orbit: Microbial
Selection Pressures in Outer Space and on Early Earth." The ISME Journal, vol. 5, no. 10, 2011,
pp. 1671–1682., doi:10.1038/ismej.2011.46
• Aditiawat.P.,Yohandini.H.,Madayanti.F., Akhmaloka.Microbial Diversity of Acidic Hot Spring
(Kawah Hujan B) in Geothermal Field of Kamojang Area, West Java-Indonesia, The Open
microbiology journal 2009; 3: 58–66.,doi: 10.2174/1874285800903010058
• Rampelotto.P.H., Extremophiles and Extreme Environments, Life (Basel). 2013 Sep; 3(3): 482–
485.
• Published online 2013 Aug 7. doi: 10.3390/life3030482
• http://www.waterencyclopedia.com/La-Mi/Life-in-Extreme-Water-Environments
• thoughtco.com/extremophiles-extreme-organisms