Halophile sfinal.pptx

Halophiles distribution, classification, adapation mechanisms, characteristics and applications

1. PRESENTED BY :- SADAAT ALTAF Msc.MICROBIOLOGY 2 ND SEMESTER UNIVERSITY OF KASHMIR HALOPHILES

2. CONTENTS Introduction Taxonomy & Classification Distribution Types Characteristics Adaptation mechanism Applications

3. INTRODUCTION TO HALOPHILES Halophiles (Greek word for salt loving) are microorganisms that require certain concentration of salt to survive and grow. Halophiles are represented by certain species of archeae, bacteria and eukaryotes for which the main characteristic is their salt requirement. One definition of halophiles is that of Oren, who defines them as “microorganisms with optimal growth at salt concentration of over 0.2M”. In Eubacteria, halophiles are a very heterogenous group,having members in at least eight different phyla. In Archeae, halophilism is strictly limited to members of Haloarchaea class and Nanohaloarchaea subphylum. Some eukaryotic halophiles are, alga Dunaliella salina and fungus Wallemia ichthyophaga.

4. 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, the Archeae (21.1%) , Bacteria (50.1%) and Eukarya ( 27.9%). The halophilic archeae come under the group, Euryarchaeota, which comprise a physiologically diverse group of Archaea. This euryarchaeal group currently has 50 genera and 213 species in one of family Halobacteriaceae (2016) , which are extremely halophilic, aerobic members of Archaea. DOMAIN – Archaea PHYLUM – Euryarcheota ORDER- Halobacteriales FAMILY- Halobacteriaceae

5. IMPORTANT GENERA The haloarchaea are a distinct evolutionary branch of Archaea distinguished by possession of ether linked lipids and absence of murein in their cell walls. In the order Halobacteriales there are 6 important families Halobacteriaceae ( Type genera- Halobacterium ) Haloarculaceae ( Type genera- Haloarcula ) Halococcaceae ( Type genera- Halocoocus ) Haloferacaceae ( Type genera- Haloferax ) Halorubraceae ( Type genera- Halorubrum ) Nitrialbales (Type genera – Natrialba )

6. DISTRIBUTION/ OCCURENCE Halophiles are found distributed all over the world in hypersaline environments. Hypersaline environments are generally defined as those containing salt concentrations in excess (3.5 % total dissolved salts). Many hypersaline bodies are formed by evaporation of sea water and are called thalassic with salinity upto 3-3.5 mol/L, a point at which extreme halophiles can grow eg Halobacterium . Waters in which salts are of nonmarine proportion, due to precipitation of NaCl , leaving high concentration of potassium and magnesium salts are called Athalassic which mark the upper limit of resistance of all biological forms. They are found in natural hypersaline brines in arid, coastal and even deep sea locations as well as in artificial salterns used to mine salts from the sea. They inhabit natural environments high in salt such as solar evaporation ponds and salt lakes or artificial saline habitats such as surfaces of heavily salted foods, like certain fish and meats.

7. They are found in marine salterns, salt marshes, subterranean salt deposits, carbonate springs, alkaline soils and soda lakes. The two largest and best studied hypersaline lakes are 1. Great salt lake in Utah ,USA in which ratio of ions is similar to that in seawater but absolute concentration of ions are about 10 times more than sea water. It is slightly alkaline in pH 2. Dead Sea in the middle east between Jordan an Israel which contains very high concentration of magnesium salts and relatively lower concentration of sodium ions. It is slightly acidic in pH Many small evaporation ponds or sabkhas are found near coastal areas. Notable among these are Solar lake,Gavish Sabkha and Ras Muhammad Pool near Red Sea coast. Hypersaline evaporation ponds have also been found in Antarctica (Deep Lake , Organic Lake ) several of which are stratified with respect to salinity. A number of alkaline hypersaline soda brines also exist including the Wadi Natrun lakes of Egypt, Lake Magadi in Kenya and Great Basin lakes of Western United States, several of which are intermittently dry. Soda brines are lacking in magnesium and calcium divalent cations because of their low solubility at alkaline ph

8. Soda lakes are highly alkaline hypersaline environments and their water chemistry resembles that of hypersaline lakes such as Great salt lake but because high levels of carbonate minerals are also present in the surrounding strata ph of soda lakes is quite high Marine salterns are also habitats for extreme halophiles . These are small, enclosed basins filled with seawater that are left to evaporate, yeilding solar sea salt. As salterns approach minimum salinity limits for extreme halophiles, the water turns reddish purple in color due to massive growth called bloom of Halophilic Archaea (due to presence of carotenoids and other pigments). Extreme halophiles are also present in highly salted foods such as certain types of sausages, marine fish and salted pork. Artificial salterns that have been constructed for production of sea salts can also harbour halophiles. Hypersaline can also occur in deep sea basins created by evaporation and flooding of ancient seas.

9. TYPES OF HALOPHILES Halophiles generally require about atleast 1.5 M NaCl (8%) , 3-4 M NaCl (17-23%) for optimal growth but still some survive at salt concentration of about 36%. Halophiles are categorized into 3 types on basis of their requirement of NaCl or by the extent of their halotolerance Slightly Halophilic - they grow best in concentrations of salt around 2-5% eg Erythrobacter flavus , Staphylococcus aureus Moderate Halophiles - they grow best in concentrations of salt around 5-20% eg Desulfohalobium Extreme Halophiles – they grow best at very high salt concentrations around 20-30% with aleast 9% requirement for salt and optimum 12-23% eg Salinibacter ruber , Halobacterium salinarium Halotolerant organisms are those which can withstand or toleate some reduction in water activity of their environment but grow best in absence of added solute.

10. CHARACTERISTICS OF HALOPHILES Most of the halophiles are aerobic chemoorganotrophs with respiratory metabolism. Aerobic halophiles include Halomonas halmophila a nd anaerobic halophiles include Halobacteriods halobius . On defined media, they use carbohydrates or simple compouns like glycerol and organic or amino acids as their carbon source. They are found in variety of shapes including cubes, pyramids in addition to rods and cocci . They are usually non motile but few strains are motile by archealla . They reproduce by binary fission and do not form spores Halobacterium was first to be described in this group. Natronobacterium , Nitronomonas differ from other extreme halophiles in being extremely alkaliphilic as well as halophilic . Extremely halophilic archaea stain gram negative

11. Genomes of Halobacterium and Halococcus are unusual in that large plasmid containing upto 25-30% of total cellular DNA are often present. Plasmids from extreme halophiles are among largesr naturally occuring plasmids known and might actually be small chromosomes. BACTERIORHODOPSINS Species of Halobacterium carry out light driven synthesis of ATP which occurs without chlorophyll pigments . They have Light sensitive pigments with red and orange carotenoids called bacteriorubrins under low aeration they synthesize and insert protein bacteriorhodopsin into cell membrane that mediates ATP production and supports slow growth of the organism under anoxic conditions. Halorhodopsins are also present which pump chlorine ions into the cell. Sensory rhodopsins control photaxis that is the flagellar rotation, moving towards light.

12. ADAPTATION MECHANISM Microbial cells must withstand osmotic forces that withstand life. Halophiles use two strategies to cope with osmotic stress Compatible solutes :- They increase cytoplasmic osmolarity by accumulating small organic molecules called compatible solutes which include glycine , betaine , polyols , ectione and amino acids. These counteract the tendency of cells to become dehydrated under conditions of high osmotic strength by placing cells in positive water balance. Salt In Approach :- some halophiles use Na/K antiporters and K symporters to concentrate KCl and NaCl to levels equivalent to external environment. The protiens of these microbes have hydrophobic amino acid residues which tend to be loacted on surface of folded protein, where they attract cations , which form a hydrated shell around the protein thereby maintaining its solubility. Cell wall of Halobacterium is composed of glycoproteins and stabilized by Na. Sodium ions bind to outer surface of cell wall and are essential for maintaining cellular integrity. When insufficient Na is present , cell wall breaks apart and cell lyses. Ribosomes also require high K levels for stability. Cellular components exposed to external environment require high Na whereas internal components require high K.

13. APPLICATIONS Industrial application Carotene from carotene rich halobacteria and halophilic algae can be used as food additive or as food coloring agent. it may also improve dough quality for baking bread. Halophilic organisms can be used in fermentation of soy sauce and Thai fish sauce eg Halobacterium salinarium Ectione is commercially produced by extracting the compound from halophilic bacteria Halomonas elongata by bacterial milking process . It can protect unstable enzymes, nucleic acid against high salinity, thermal denaturation and desiccation and freezing therefore it can be used to increase shelf life of enzymes. It stabilizes activity of trypsin and chymotrypsin Rhodopsins can reduce sunburn when exposed to UV light It also inhibits aggregation and neurotoxicity of Alzheimer’s beta amyloid . They store Poly beta hydroxyalkanoate (PHA) which is used for production of biodegradable plastics. Thus they play a significant role in industry with large number of applications with fermented food products, cosmetics, preservatives, manufacturing of bioplastics , photoelectric devices, artificial retinas, holograms, biosensors etc.

14. Medical application the great metabolic diversity and the characteristics of halophilic microorganisms makes them promising candidate and hope for drug discovery. Haloarchae were first members of archaea found to produce bacteriocins named halocins . They are peptide or protien antibiotics secreted into the environment to kill or inhibit the sensitive haloarchael strains that occupy the same niche. Environmental applications Processes of biological wastewater treatment to remove organic carbon and toxic compounds is facilitated by several halophiles eg the Dunaliella growth facilitates wastewater treatment in oxidation ponds. Studies have proved that through addition of Halobacterium salinarium degradation of wastes is improved. They can be used to remove toxic materials such as lead, phosphorus and cadmium from contaminated materials. Biofuel production the halophilic alga Dunaliella salina is commericial source of beta carotene and as potential source of glycerol production which may also be considered as a raw material for biofuel production. Genetically engineered halophilic enzymes introduced into crops can allow salt tolerance

15. Several halophiles produce extracellular polysaccharides that have applications as gelling agents, emulsifiers and also in microbially enhanced oil recovery. Certain enzymes like amylases from halophiles that are stable at high temperature and in benzene, toulene and chloroform are of potential intrest. Halophiles produce stable enzymes like DNAases, lipases, amylases, gelatinases and proteases capable of functioning under conditions that lead to precipitation or denaturation of most of the protiens and can thus have biotechnological applications. Bacteriorhodopsins from halophiles are used in holographic storage, construction of bioelectronic elements of computers and information proecessing units, nanotechnology applications such as construction of molecular sensors.