Halophiles (Introduction, Adaptations, Applications)

Introduction
Halophiles are organisms that thrive in high salt concentrations.
They are a type of extremophile organisms. The name comes from the Greek word for "salt-loving".
While most halophiles are classified into the Archaea domain, there are also bacterial halophiles and some eukaryota, such as the alga Dunaliella salina or fungus Wallemia ichthyophaga

1. Halophiles By; SanaUllah Jamil Ahmad SaeedUllah ( M.phil II)

2. I ntroduction Halophiles  are organisms that thrive in high salt concentrations. They are a type of extremophile organisms. The name comes from the Greek word for "salt-loving". While most halophiles are classified into the  Archaea  domain, there are also bacterial halophiles and some  eukaryota , such as the alga  Dunaliella salina  or fungus  Wallemia ichthyophaga

3. Habitat Habitats like soda lakes, T halassohaline , A thalassohaline , Dead Sea, C arbonate springs, S alt lakes, A lkaline soils and many others favors the existence of halophiles.

4. S alt lake bordered by Jordan to the east and  Israel and Palestine to the west ( Cyanobacteria, Dunaliella salina )

5. Utah, United States great salt lake . Average salt conc 13%, Halobacterium and Halococcus .

6. An aerial view shows the pink water of Great Salt Lake brushing up against the Eco-sculpture "Spiral Jetty" on a salt-crust shore. Image credit: Bonnie Baxter. Salt flats at Lake Magadi , Kenya. The flats are red due to the proliferation of halobacteria . Owens Lake. The pink coloration is caused by halobacteria living in a thin layer of brine on the surface of the lake bed.

7. Taxonomy Methods of chemotaxonomy,multilocus sequence analysis,numerical taxonomy,comparative genomics and proteomics have allowed taxonomists to classify halophiles. These versatile microorganisms occupy all three major domains of life i.e., Archaea 21.9% Bacteria 50.1% Eukarya . 27.9%

8. A rchaea The domain Archaea has been further divided into two subdomains, Halobacteria and Methanogenic Archaea . Halobacteria is represented by one of the largest halophile family,Halobacteriaceae with 36 genera and 129 species requiring high NaCl concentrations which discriminate them from other halophiles

9. Diversity A wide variety of halophiles including heterotrophic ( Chromohalobacter , Selina vibrio) Chemoautotrophic ( Dunaliella ) , chemolithotrophic ( marinobacter sp ) Aerobes ( Halomonas halmophila ) and anaerobes ( Halobacteroides halobius ) could be observed transforming diverse range of substrates in hypersaline habitats.

10. Types Halophiles are categorized as slight, moderate, or extreme, by the extent of their  halotolerance . Slight halophiles prefer 0.3 to 0.8 M (1.7 to 4.8% — seawater is 0.6 M or 3.5%), e.g , Erythrobacter flavus moderate halophiles 0.8 to 3.4 M (4.7 to 20%), e.g , Desulfohalobium and extreme halophiles 3.4 to 5.1 M (20 to 30%) salt content. E.g , Salinibacter ruber

11. What happens at high salinity to most organisms? The greater the difference in salt concentration between in and outside the cell - the greater the osmotic pressure (hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane due to a differential in the concentrations of solute ). If we drink salty water we desiccate the cells -enzymes and DNA denature or break! Plants : trigger ionic imbalances -damage to sensitive organelles such as chloroplast. Animals : a high salt concentration within the cells -water loss from cells -brain cells shrinkage -altered mental status, seizures, coma, death. ( Natural salts were used to remove moisture from the body during mummification).

12. Adaptations of Halophiles to their environment

13. Adaptations of halophiles to hyper saline environment (a) The integrity of non-halophile macromolecules is compromised, and the flow of water out of the cell produces a Turgor effect. ( b) Moderate halophiles maintain their structures via the synthesis of compatible organic solutes . (c) Extreme halophiles maintain their structures via equilibration of cellular and environmental salt concentrations.

14. C ellular adaptation To avoid excessive water loss under such conditions, halophiles have evolved two distinct strategies: High salt-in strategy Low-salt, organic salute-in strategy

15. High salt-in strategy A ccumulation of inorganic ions intracellularly to balance the salt concentration in their environment. This process involves the Cl - pumps that are found only in halophiles that transport Cl - from the environment into the cytoplasm. Extreme halophiles of the archaeal Halobacteriaceae family and the bacterial Halanaerbiales family maintain their osmotic balance by concentrating K+ inside cells. This is achieved by the concerted action of the membrane-bound proton-pump bacteriorhodopsin .

16. Mechanism of bacteriorohodopsin

17. Low-salt, organic solute-in strategy This strategy is adapted by moderate halophiles. Highly saline environment is incompatible for the survival of moderate halophiles. Thrive in habitats of fluctuating salinity , i.e., salt concentrations can reach molar levels and then fall to near-freshwater concentrations after a rainfall . The required adaptations involve evolution of compatible organic solutes ( osmolytes ) in the halophiles.

18. Glycine betaine in Halorhodospria halochloris was the first reported bacterial osmolyte . These substances within the cells of microorganisms are regulated according to the salt concentration outside the cell.

19. Protein adaptations A high-salt environment substantially impacts protein solubility and stability and consequently function by dehydration. A noticeable difference between proteins from halophiles and nonhalophiles is that those of halophiles have a larger proportion of glutamate and aspartate on their surfaces. Also they have less hydrophobic amino acids. T he acidic residues on halophilic proteins bind hydrated cations which would maintain a shell of hydration around the protein

20. Cell membrane adaptation The membranes of extremely halophilic Archaea are characterized by the abundance of a   phosphatidyl glycerol methyl phosphate (PGP-Me). These membranes are stable in concentrated 3-5 m NaCl solutions. W hereas membranes of non- halophilic Archaea , which do not contain PGP-Me, are unstable and leaky under such conditions . Halobacterium halobium   Halobacterium salinarum Archaeal lipids are characterized by ether linkages and isoprenoid chains, mainly phytanyl in contrast to the ester linkages and straight fatty acyl chains of non- Archaea .

21. Applications of Halophiles

22. Applications of halophiles Industrial application: carotene from carotene rich halobacteria and halophilic algae can be used as food additives or as food- coloring agents it may also improve dough quality of backing breed. Halophilic organisms used in the fermentation of soy sauce and Thai fish sauce . Halobacterium salinarum Halobacterium  sp. SP1

23. Ectoine Ectoine is commercially produced by extracting the compound from halophilic bacteria. Industrial process for mass production of ectoine and hydroxyectoine were developed by using Halomonas elongata and Marinococcus M52, respectively. This procedured is based on bacterial milking.

24. One of the most common osmotic solutes in the domain Bacteria is ectoine (1,4,5,6-tetrahydro-2- methyl-4-pyrimidine carboxylic acid ). It was I st discovered in E ctothiorhodspira halochloris .

25. Ectoine can protect unstable enzymes nucleic acid against high salinity thermal denaturation desiccation and freezing. Therefore increased the shelf life of enzymes . Stabilizes the activity of trypsin and chymotrypsin. It can also reduced the sun burn cell when exposed to U.V light . Ectoine also inhibits aggregation and neurotoxicity of Alzheimer’s β-amyloid.

26. Poly-β- hydroxyalkanoate production by halophilic bacteria Poly- β- hydroxyalkanoate (PHA ), a polymer containing β- hydroxybutyrate and β- hydroxyvalerate units, is accumulated by many prokaryotes, Bacteria as well as Archaea , as a storage polymer. It is used for the production of biodegradable plastics with properties resembling that of polypropylene Halomonas boliviensis , H. mediterranei

27. Medical application Haloarchaea were the first members of archaea found to produce bacteriocins , named halocins . They are peptide or protein antibiotics secreted into the environment to kill or inhibit the sensitive haloarchaeal strains that occupy the same niche.

28. Environmental Several processes have been proposed for the biological treatment of such wastewaters to remove organic carbon and toxic compounds. S everal dunaliella growth facilitates the waste water treatment in oxidation ponds . Optimization study has been proved through Halobacterium salinarum was added to improve degradation .

29. Biofuel production The halophilic alga Dunaliella salina commercial source of β-carotene and as a potential source of glycerol production, may also be considered as the raw material for biofuel production.

30. Enzymes from halophile microorganisms

31. Other applications Increasing crude oil extraction through microbial enhanced oil recovery (MEOR). Genetically engineering halophilic enzymes encoding DNA into crops to allow for salt tolerance. A well known study has been conducted on genetic strain holomonas sp , bacilus gabsonii EN4.

32. References Gupta, R.S.; Naushad , S.; Baker, S. Phylogenomic analyses and molecular signatures for the class Halobacteria and its two major clades: A proposal for division of the class Halobacteria into an emended order Halobacteriales and two new orders, Haloferacales ord nov and Natrialbales ord. nov. , containing the novel families Haloferacaceae fam. nov. and Natrialbaceae fam. nov. Int. J. Syst. Evol . Microbiol . 2015 , 65 , 1050–1069. Temperton B, Giovannoni SJ (2012)  Metagenomics Microbial diversity through a scratched lens. Curr Opin Microbiol 15: 605-612. Moreno ML, Perez D, García MT, Mellado E (2013)  Halophilic bacteria as a source of novel hydrolytic enzymes. Life 3: 38-51. Waditee-Sirisattha R, Kageyama H, Takabe T (2016)  Halophilic microorganism resources and their applications in industrial and environmental biotechnology. AIMS Microbiol 2: 42-54 Bose U, Hewavitharana AK, Ng YK, Shaw PN, Fuerst JA, et al. (2015) LC-MS-Based metabolomics study of marine bacterial secondary metabolite and antibiotic production in salinisporaarenicola . Mar Drugs 13: 249-266. Litchfield CD (2011) Potential for industrial products from the halophilicArchaea . IndMicrobiolBiotechnol 38: 1635-1647 Bose A, Chawdhary V, Keharia H, Subramanian RB (2014) Production and characterization of a solvent tolerant protease from a novel marine isolate  Bacillus   tequilensis P15. Ann Microbiol 64: 343-354.