Halophiles are salt-loving microorganisms that thrive in saline environments. They include archaea, bacteria, and eukaryotes found in places like salt lakes and salt marshes. The plasma membrane of halophiles like Halobacterium salinarum contain the light-absorbing pigment bacteriorhodopsin, which functions as a light-driven proton pump by using the energy from absorbed photons to move protons across the membrane. This creates a proton gradient that is used to generate chemical energy via ATP synthesis. Bacteriorhodopsin and related proteins from extremophilic microbes have applications in areas like biotechnology and medicine due to their stability and ability to function under extreme conditions.

1. HALOPHILES
HALOPHILIC MEMBRANE VARIATION, ELECTRON TRANSPORT
APLICATION OF THERMOPHILES AND EXTREMOPHILES

2. What is halophiles ?
• Halophiles, salt‐loving organisms that flourish in saline environments, are classified as slight,
moderate or extreme, depending on their requirement for sodium chloride. While most marine
organisms are slight halophiles, moderate and extreme halophiles are generally more specialized
microbes inhabiting hypersaline environments found all over the world in arid, coastal and deep‐sea
locations, underground salt mines and artificial salterns. Halophilic microorganisms include
heterotrophic, phototrophic and methanogenic archaea, photosynthetic, lithotrophic and
heterotrophic bacteria and photosynthetic and heterotrophic eukaryotes.
• Examples - Halobacterium salinarum

3. Key features of Halophilic bacteria.
• Key Concepts
• Halophiles are salt‐loving organisms that inhabit saline and hypersaline environments and include
prokaryotic (archaeal and bacterial) and eukaryotic organisms.
• The bacteria lives in the brine pond, salt lakes, and dead sea.
• Halophiles may be classified as slight, moderate or extreme, and as obligate halophiles or
halotolerant.
• Many halophiles accumulate compatible solutes in cells to balance the osmotic stress in their
environment.
• Some halophiles produce acidic proteins that function in high salinity by increasing solvation and
prevent protein aggregation, precipitation and denaturation.
• Halophiles and their biomolecules are useful for applications in biotechnology, medicine and
industry.

4. To survive the condition the Halophilic bacteria employ two different strategies to prevent the
desiccations through osmotic movement of water out of there cytoplasm. Both strategies worked by
increasing the internal osmolarity of the cells.
 It can grow where the salt concentration is 4M to 8M , results from the water evaporation,
Halophilic can not live in the salt concentration lower of 3M.
This organisms are anaerobic and normally use oxygen to oxidized the organic fuel molecules.

5. PLASMA Membrane of halobacterium
• Plasma membrane of Halobacterium salinarium contains with the light absorbing pigments, like
Bacteriorhodopsin.
• Which contains with the Retinal bounded bacteriorhodopsin, can absorb a photons and undergoes
photo-isomerization to 13 cis Retinal.
• The restoration of all trance retinal is accompanied by the out words movement of proton through
the plasma membrane.
• The bacteriorhodopsin with only 247 amino acid residues known as the simplest light driven photon
pump.
• The three dimensional structure of the pump transfer the photon across the membrane.

6. LIGHT-DRIVEN PROTONE PUMPING BY BACTERIORHODOPSIN
• Bacteriorhodopsin is a protein used by Archaea, most notably by Halobacterium, a class of the
Euryarchaeota. It acts as a proton pump; that is, it captures light energy and uses it to move protons
across the membrane out of the cell. The resulting proton gradient is subsequently converted into
chemical energy.

7. FUNCTION OF BACTERIORHODOPSIN
Bacteriorhodopsin is a light-driven proton pump. It is the retinal molecule that changes its
conformation when absorbing a photon, resulting in a conformational change of the surrounding
protein and the proton pumping action.
It is covalently linked to Lys216 in the chromophore by Schiff base action. After photoisomerization
of the retinal molecule, Asp85 becomes a proton acceptor of the donor proton from the retinal
molecule. This releases a proton from a "holding site" into the extracellular side (EC) of the
membrane.
Reprotonation of the retinal molecule by Asp96 restores its original isomerized form. This results in
a second proton being released to the EC side. Asp85 releases its proton into the "holding site,"
where a new cycle may begin.

8. The bacteriorhodopsin molecule is purple and is most efficient at absorbing green light (wavelength
500-650 nm, with the absorption maximum at 568 nm). Bacteriorhodopsin has a broad excitation
spectrum. For a detection wavelength between 700 and 800 nm, it has an appreciable detected
emission for excitation wavelengths between 470 nm and 650 nm (with a peak at 570 nm). When
pumped at 633 nm, the emission spectrum has appreciable intensity between 650 nm and 850 nm.
Bacteriorhodopsin belongs to the microbial rhodopsin. They have similarities to vertebrate
 Rhodopsin, the pigments that sense light in the retina. Rhodopsin also contain retinal; however, the
functions of rhodopsin and bacteriorhodopsin are different, and there is limited similarity in their
amino acid sequences.
 Both rhodopsin and bacteriorhodopsin belong to the 7TM receptor family of proteins, but rhodopsin
is a G protein-coupled receptor and bacteriorhodopsin is not. In the first use of electron
crystallography to obtain an atomic-level protein structure.

9. It was then used as a template to build models of G protein-coupled receptors before
crystallographic structures were also available for these proteins.
Many proteins have homology to bacteriorhodopsin, including the light-driven chloride pump halo
rhodopsin (for which the crystal structure is also known), and some directly light-activated channels
like channel rhodopsin.
All other phototrophic systems in bacteria, algae, and plants use chlorophylls or bacteriochlorophylls
rather than bacteriorhodopsin. These also produce a proton gradient, but in a quite different and
more indirect way involving an electron transfer chain consisting of several other proteins.
Furthermore, chlorophylls are aided in capturing light energy by other pigments known as "antennas";
these are not present in bacteriorhodopsin-based systems. It is possible that phototroph
independently evolved at least twice, once in bacteria and once in archaea.

10. Application of thermophiles and extremophiles
• THERMOPHILES - A thermophile is an organism—a type of extremophile—that thrives at
relatively high temperatures, between 41 and 122 °C (106 and 252 °F). Many thermophiles are
archaea. Thermophilic eubacteria are suggested to have been among the earliest bacteria.
• Thermophiles are found in various geothermally heated regions of the Earth, such as hot springs like
those in Yellowstone National Park (see image) and deep sea hydrothermal vents, as well as decaying
plant matter, such as peat bogs and compost.
• Thermophiles can survive at high temperatures, whereas other bacteria would be damaged and
sometimes killed if exposed to the same temperatures.
• The enzymes in thermophiles necessarily function at high temperatures. Some of these enzymes are
used in molecular biology, for example, heat-stable DNA polymerases for PCR), and in washing
agents. Ex- Sulfolobus solfataricus and Sulfolobus acidocaldarius

11. EXTREMOPHILES- An extremophile is an organism that thrives in extreme environments.
Extremophiles are organisms that live in "extreme environments," under high pressure and temperature.
Bacteria often form on the rocks near the hydrothermal vents.
APPLICATION-
The enzyme Thermo-alkalophilic catalase, found in Thermus brockanus [found in Yellowstone National
Park] 𝐻2 𝑂2 to O2 and water.
The enzyme Catalase operates over a temperature range from 30^c to 95^c. and pH range from 6-10.
This catalase [Aspergillus niger] is the extremely stable compound to other catalase can act on above
80^c and very high pH 10.
Catalase will have application for removal of Hydrogen peroxide in industrial process, such as pulp,
paper bleaching, textile bleaching,
Such enzyme Taq-polymerase and some Bacillus enzymes used in clinical diagenesis, and starch
liquefaction are produced commercially by several biotechnology process.

12. WHAT IS EXTREMOZYME?
Extremophilic microorganisms have established a diversity of molecular strategies in
order to survive in extreme conditions. Biocatalysts isolated by these organisms are
termed extremozymes, and possess extraordinary properties of salt allowance,
thermostability, and cold adaptivity. Extremozymes are very resistant to extreme
conditions owing to their great solidity, and they pose new opportunities for
biocatalysts and biotransformation's, as well as for the development of the economy
and new line of research, through their application. Thermophilic proteins,
acidophilic proteins, and halophilic proteins have been studied during the last few
years. Amylases, proteases, lipases, pullulans, cellulases, chitinases, xylanases,
pectinases, isomerases, esterase, and dehydrogenases have great potential
application for biotechnology, such as in agricultural, chemical, biomedical, and
biotechnological processes.

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