User:AshleyONeill/Haloarchaea

Living Environment
Haloarchaea require salt concentrations in excess of 2 M (or about 10%) to grow, and optimal growth usually occurs at much higher concentrations, typically 20–30% (3.4 - 5.2 mol/L of NaCl). However, haloarchaea can grow up to saturation (about 37% salts). Optimal growth also occurs when pH is neutral or basic and temperatures at 45°C. Some haloarchaea though can grow even when temperatures exceed 50°C.

Haloarchaea are found mainly in hypersaline lakes and solar salterns. Their high densities in the water often lead to pink or red colourations of the water (the cells possessing high levels of carotenoid pigments, presumably for UV protection). The pigmentation will become enhanced when oxygen levels are low due to an increase in a red pigmented ATP. Some of them live in underground rock salt deposits, including one from middle-late Eocene (38-41 million years ago). Some even older ones from more than 250 million years ago have been reported. Haloarchaea is also used to treat water water that is high in salinity. This is due to its ability to its ability to withstand high nutrient levels and the heavy metals that may be present.

As exophiles
Haloarchaea have been proposed as a kind of life that could live on Mars; since the Martian atmosphere has a pressure below the triple point of water, freshwater species would have no habitat on the Martian surface. The presence of high salt concentrations in water lowers its freezing point, in theory allowing for halophiles to exist in saltwater on Mars. Recently, haloarchaea was sent 36 km (about 22 miles) up into Earths atmosphere, within a balloon. The two types that were sent up were able to survive the freezing temperatures and high radiation levels. This only further extends the theory that halophiles could exist on Mars.

Medical use
Certain types of haloarchaea have been found to produce carotenoids, which normally has to be synthesized using chemicals. With haloarchaea naturally producing it, there is not a natural way to synthesize carotenoids for medical use. Haloarchaea has also been proposed to help meet the high demand of carotenoids by pharmaceutical companies due to how easy it can be grown in a lab. Genes in Haloarchaea can also be manipulated in order to produce various stands of carotenoids, further helping meet pharmaceutical companies needs.

Haloarchaea is also present within the human gut, mostly predominant in the gut of people who live in Korea. Haloarchaea are most abundant in Koreans guts rather than methanogens due to their saltier diets. This also shows that the archaeome in the human gut can vary drastically depending on region and what is eaten.

Climate change
Haloarchaea have been proposed that certain types can be used to make biodegradable plastics, which could help decrease plastic pollution. Haloarchaea are able to produce polyhydroxyalkanote (PHA), polyhdroxybutyrate (PHB) and polyhydroxyvalerate (PHV), when exposed to certain conditions. For large scale production of these bioplastics, haloarchaea is favored due to the low cost, fast growth, and lack of need to sterilize area due to the salty environment they prefer. They are also a cleaner option for bioplastics due to them not needing chemicals for cell lysis and have a higher recyclability of the process.

Certain types of haloarchaea have also been found to poses denitrifying characteristics. If haloarchaea are complete denitrifies, they could aid salt marsh and other salty environments by buffering these areas of nitrate and nitrite. This could help animal diversity and decrease pollution with in these waterways. However, when tested in the lab, haloarchaea have been found to be partial denitrifies. This means that if haloarchaea are used to treat areas that are high in nitrite and nitrate, they could contribute to nitrogen contaminates and cause an increase in ozone depletion, furthering climate change. The only type of haloarchaea that has been found to reduce nitrogen pollution to atmospheric nitrogen has been Haloferax mediterranei. This shows that haloarchaea may be contributing to nitrogen pollution and isn't a suitable solution to reducing nitrate and nitrite within high salinity areas.