User:Rehanna Thobani/sandbox

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 20–25%. However, Haloarchaea can grow up to saturation (about 37% salts).

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).

Adaptations to Environment
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 as the cells possessing high levels of carotenoid pigments, presumably for UV protection.

Haloarchaea require a salt concentration of more than 2 M (or about 10%) to grow, and optimal growth usually occurs at much higher concentrations, typically 20–25%. However, Haloarchaea can grow up to saturated salt concentrations, which corresponds to about 37% salts. Most microorganisms can’t multiply with when the water activity (aw) is lower than 0.90, yet in the environments of saturated salt, aw is close to 0.75, which is inhibitory to the growth of most microbes. The number of solutes also causes osmotic stress on microbes, which can cause cell lysis, unfolding of proteins and inactivation of enzymes when there is a large enough imbalance. Haloarchaea have evolved mechanisms to evade these environmental obstacles.

One strategy haloarchaea use to allow them to thrive in the conditions of low aw and high osmotic pressure is to retain compatible solutes in their intracellular space. A common compatible solute used by haloarchaea is potassium chloride (KCl), referred to as the “salt-in” method, where the cell accumulates a high internal concentration of potassium. Because of the elevated potassium levels, haloarchaea have specialized proteins which have a highly negative surface charge to tolerate high potassium concentrations. .

Haloarchaea use glycerol as an important carbon and energy source and it is often present in high salt environments due to another organism, Dunaliella, which is a eukaryotic microalga that produces large amounts of glycerol as a compatible solute. Haloarchaea do not use glycerol as a compatible solute, but many break down glycerol in catabolism.

Rehanna Thobani (talk) 00:12, 7 October 2017 (UTC)

Adaptations to the Environment


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 as the cells possessing high levels of carotenoid pigments, presumably for UV protection. Haloarchaea require a salt concentration of more than 2 M (about 10%) to grow, and optimal growth usually occurs at much higher concentrations, typically 20–25%, though they can grow up to saturated salt concentrations (37%). A water activity (aw) lower than 0.90 is inhibitory to most microbes, yet haloarchaea can grow at an aw close to 0.75. The number of solutes causes osmotic stress on microbes, which can cause cell lysis, unfolding of proteins and inactivation of enzymes when there is a large enough imbalance. Haloarchaea combat this by retaining compatible solutes such as potassium chloride (KCl) in their intracellular space to allow them to balance osmotic pressure. Retaining these salts is referred to as the “salt-in” method where the cell accumulates a high internal concentration of potassium. Because of the elevated potassium levels, haloarchaea have specialized proteins which have a highly negative surface charge to tolerate high potassium concentrations.

Haloarchaea have adapted to use glycerol as a carbon and energy source in catabolic processes, which is often present in high salt environments due to Dunaliella species that produce glycerol in large quantities.

Rehanna Thobani (talk) 06:21, 20 November 2017 (UTC)

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