Salt as a Method of Water Conservation: Archaea in Salt Water Lakes
Salt lakes are a harsh environment which has highly saline conditions who grow in extremophiles including a diverse group of halophiles. Halophiles are live in the deep sea, salt mines, and crystalized ponds also. This type of microorganisms has variation in the fluidity of membrane as well as salt tolerance. Growing at a salt concentration higher than 100 gl-1. Archaea represents the largest family of halophilic archaea; Halobacteriacea. Halobacteriacea is aerobic halophilic archaea and the members of the genus are Haloarcula and Haloferax. They have the ability to grow anaerobically. Halophilic archaea allow extreme conditions such as optimum temperature, pH, pressure, and salinity to optimal growth. Most of the halophilic archaea have orange, red, and purple pigments. Haloarchaea was found in the Dead Sea, the Great Salt Lake (Utah), Lake Magadi (Kenya). Halobacteriacea have been used in so many biotechnological applications in this era.
Some microbial species such as halophilic archaea have composition and nature to favor in hypersaline habitats. These extreme conditions have allowed developing their skills for surviving in nature. Haloarchaea thrives in environments where salt concentration approaches saturation such as natural brines, salt lakes, and the Dead sea. The worldwide natural salt deposits vary from Pliocene to Silurian. Within the sixties, the first cultivations of halophilic microorganisms for about 250 million years ago in salt sediments were rumored and raised worldwide skepticism (a pinch of salt). These hypersaline ecosystems have environmental conditions such as high alkalinity, low concentration of oxygen, and high UV irradiation. Hypersaline habitats have been divided into two types; 1) thalassohaline and 2) thalassohaline waters. Thalassohaline water has an ionic composition similar to seawater with NaCl as the main salt. Athalossohaline water is not directly connected to marine nature. Thalassohaline water is known as brines (The Dead Sea). These brines are formed by the dissolution of mineral salt deposits of predominant origin, which one dominated by K+, Mg2+, Na+, and CO3 2-. There are some halophilic archaea that have been isolated including Haloferax mediterranei, Haloferax gibbonsii, Haloferax denitrificans, Halogeometricum borinquense, Halococcus saccharolyticus, Haloterrigena thermotolerans, Halorubrum saccharovorum, Halorubrum coriense, Haloarcula hispanicaand Haloarcula, Halobacterium salinarum. A recent study was shown that red heterophilic microbes, are no less salt-dependent and salt-tolerant than the most halophilic among the archaea.
There were studies done by scientists where the hypersaline lakes at the Vestfold Hills lake system of Eastern Antarctica are subject on microbes. This lake is 36m deep with a salinity of 320 gl-1 and temperature is (-14) – (-18) OC, and dominated by the family Halobacteriacea.
Lake Magadi (Kenya) is also an alkaline hypersaline lake in the East African Rift Valley. The pH is this lake about 10 and the microbial community dominates with the number of Halobacteriacea.
Halophilic archaea play various roles in their habitats by degrading hydrocarbons. Specifically, archaea involve in the degradation of petroleum hydrocarbons and halogenated hydrocarbons. Continuous extraction, purification, transport, and use of petroleum continuously release extremely hazardous contaminants into ecosystems. The dangerous effects of hydrocarbon pollution on plants, animals, human health, and also the atmosphere. Interestingly, a study by Minai-Teh-rani and colleagues showed that though there was a 40 %(v/w) degradation of fossil oil in soil samples after 120 days, degradation fell to solely 12 that when NaCl was added to a concentration of five zip. The severe saline and hypersaline environments in that halophiles will survive to justify their quality for bioremediation of contaminants which embrace hydrocarbons and chlorine compounds. Hydrocarbon biodegradation during hypersaline or marine surroundings is vital because it considers the bioremediation of crude pollution of salt marshes and industrial wastewaters.
Most mixed microbial populations have not been characterized in terms of their biodegradation capability, although an extreme halophilic archaeal population oxidizes petroleum hydrocarbons at salinities of 15% (w/v) NaCl. Three extraordinarily halophilic archaeal strains, Haloferax, Halobacterium and Halococcus isolated on the idea of petroleum utilization additionally degraded n-alkanes and mono and polyaromatic compounds because the sole sources of carbon and energy within the presence of 26th NaCl have reported the isolation of many strains of archaea that degrade n-alkanes (heptadecane and eicosane) within the presence of 22.5% NaCl from a shallow crystallizer pond (Camargue, France) with no identified contamination history. Experiments additionally showed that the isolate was able to degrade a combination of acyclic and aromatic hydrocarbons together with tetradecane, hexadecane, eicosane, heneicosane, pristane, acenaphthene, phenanthrene, anthracene, and 9-methyl anthracene within the presence of >20% NaCl were among the first to report the isolation of a halophilic archaea strain that was recently classified as Haloarcula vallismortis from a salt marsh close to the city of Aigues-Mortes in southern France.
The persistence and toxicity of halogenated compounds are of prime environmental concern, ex: some substances are related to the destruction of the ozone layer, and therefore their use has been prohibited in most countries. These halogenated compounds absorb earth radiant energy 1000–24,000 times a lot of efficiently than will carbon oxide, and therefore the world warming potential of chlorofluorocarbons and hydrofluorocarbons. So the degradation process of halogenated hydrocarbons is due to the activity of fungi as well as the activity of archaea.
Halophilic archaea have different adaptations such as cells accumulating high KCl intracellular concentrations or some osmolytes (2-sulfotrehalose) to affect high ionic strength, roteins become stable and active inside cytoplasm containing high KCl concentrations, Amino acidic remainder, mainly on halophilic proteins’ surface, the cellular membrane has different structure and composition, halophilic microbes contain an important quantity of salt resistance genes from their genome. Due to these adaptations, they are used in lots of biotechnological, and biomedical applications in nowadays. Thus, enzymes, carotenoids, PHA/s & PHB/s, halocins (bacteriocin-like peptides), bioremediation of metals, and Halobacterium salinarum species act as bacteriorhodopsin (Holographic storage material, computer memory, and processing unit) biodegradation process as discussed above.
Charotinoides are natural pigments. The most abundant ones are in the range of colorless to yellow, orange, and red. Plants, algae, cyanobacteria, yeast, and fungi are producing these bio pigments. Carotenoids consist of C40 hydrocarbon and synthesize families of archaea known as Haloferacaceae and Halobacteriaceae. The C50 carotenoids biosynthesis was first described on Halobacterium cutirubrum belongs to the family of Halobacteriaceae. Biosynthesis is caused by low oxygen tension and high light intensity, osmotic stress, and the presence of different compounds such as aniline. Carotenoid production by can be improved by genetic modification of halophilic archaea or by modifying optimum conditions such as nutrition, growth pH, or temperature. Carotenes and Xanthophyll are present in animals and mammals. Animals are not able to synthesize carotenoids which have the power of acting as an antioxidant.
Halophilic archaeal enzymes are active and stable at high salinity conditions that are environments usually adverse to different enzymes. Many enzymes from haloarchaea with, such as glycosyl hydrolases (hydrolyzing glycosidic bond between carbohydrates) such as cellulases and chitinases, proteases (proteolytic enzymes), lipases and esterases (hydrolyze ester bonds between fatty acids) are characterized, however, no large-scale applications are reported, however. Compared to non-halophilic enzymes, they're characterized by comparatively higher usage of acidic residues, a low frequency of lysine, and a high prevalence of amino acids with a low hydrophobic character. Under these conditions, halophilic enzymes might be utilized in biotechnological applications in non-aqueous media.
PHAs (Polyhydroxyalkanoates) are made within the stationary part of growth, once the medium is deficient in some essential nutrients however a carbon supply is offered in excess, and polyesters are composed of hydroxy fatty acids, synthesized and keep as insoluble inclusions within the living substance. There is a wide variety of PHAs depending on their microbial strain, growth conditions, and carbon source. PHAs can be divided, according to the type of the monomers include; PHB (poly-3-hydroxybutyrate), P3HP (poly-3-hydroxypropionate), P4HB (poly-4-hydroxybutyrate), PTE (polythioester), PLA (polylactic acid), and PHV (polyhydroxyvalerate)
Archaea remediate metals such as Arsenite, Mercuric mercury, Cadmium, Uranium, etc. As an example, there was a recent metagenomic study of Diamante Lake (Argentina) and found arsenate reduction and arsenite oxidation genes of haloarchaea and there was another research done in Yellowstone National Park (USA) in mercury containing hot spring found deeply rooted mercury reductase genes associated with Archaea. Bioremediation of metals converts the toxic redox state into its non-toxic redox state or it may convert soluble metal redox states to insoluble redox states. As a result of this process, it will be removed the toxicity of heavy metals through reactions or through sorption into biomass. Arsenite oxidized into less toxic arsenate and Mercuric mercury oxidized into non-toxic mercury. Uranium also oxidized UVI to UIV. So the haloarchaea can be used in the removal of heavy metals in hypersaline environments and wastewater and also this process is important to radioactive metals because these archaeal strains have a high tolerance of radioactivity.
Because of the influence of human activities, saltwater environments are threatening such as: surface diversion inflows, salinization, mining activities, pollution, and climate changes.
Diversion of inflow for agricultural and humans is the most important activity. Changes of local climate, falling groundwater levels, and the loss of islands happen to activities of mankind.
The process of salinization involves the making movable of salts dissolved in underground water because the formation rises following a decrease within the quantity of underground water transpired by constituted plants and once close to the surface, capillarity brings them to the surface.
Pollution of salt lakes can be harmful to aquatic life on saltwater lakes. Wastewater of farms, domestic, industrial, and pesticides are the pollutants which we are using and it can be affect to the aquatic lives.
Mining is the process that extracting of valuable minerals from the earth. This process is an important human activity and also it is disturbing to the environment along with the dry salt lakes physically.
Climate changes directly affect to the salt lakes. If the climate changes, precipitation, and evaporation of salt lakes also change. Therefore global warming happens to influence of humans and disturb the environment of salt lakes.
In conclusion, Haloarchaea can survive any harsh environment likewise hypersaline water, and their regulations are used in investigations for the production of transgenic crops and new products recently. Recent research suggested due to the presence of halite on Mars and are moons in the solar system. To increase the ability for finding extraterrestrial life, halite-containing regions and very small particles, which might be living fossils should be focused on. There is a beautiful quote about lakes related “We forget that the water cycle and the life cycle are one.” — Jacques Yves Cousteau. In my opinion, it would be described about saving the water and environment because if we have not enough water to our domestic usage we cannot survive our lives. Therefore if there is no water cycle really we do not have a life cycle. In contrast save water, sources include salt lakes in nature.
