Haloarchaea
Encyclopedia
Haloarchaea are microrganisms and members of the halophile
community, in that they require high salt concentrations to grow. They are a distinct evolutionary branch of the Archaea
, and are generally considered extremophiles, although not all members of this group can be considered as such.
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).
One of the more unusually shaped Haloarchaea is the "Square Haloarchaeon of Walsby." It was classified in 2004 using a very low nutrition solution to allow growth along with a high salt concentration, square in shape and extremely thin (like a postage stamp
). This shape is probably only permitted by the high osmolarity of the water, permitting cell shapes that would be difficult, if not impossible, under other conditions.
; since the Martian atmosphere has a pressure below the triple point
of water, freshwater species would have no habitat on the Martian surface.
Halophile
Halophiles are extremophile organisms that thrive in environments with very high concentrations of salt. The name comes from the Greek for "salt-loving". While the term is perhaps most often applied to some halophiles classified into the Archaea domain, there are also bacterial halophiles and some...
community, in that they require high salt concentrations to grow. They are a distinct evolutionary branch of the Archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...
, and are generally considered extremophiles, although not all members of this group can be considered as such.
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).
Cellular shapes
Haloarchaea are often considered pleomorphic, or able to take on a range of shapes—even within the one species. This makes identification by microscopic means difficult, and it is now more common to use gene sequencing techniques for identification instead.One of the more unusually shaped Haloarchaea is the "Square Haloarchaeon of Walsby." It was classified in 2004 using a very low nutrition solution to allow growth along with a high salt concentration, square in shape and extremely thin (like a postage stamp
Postage stamp
A postage stamp is a small piece of paper that is purchased and displayed on an item of mail as evidence of payment of postage. Typically, stamps are made from special paper, with a national designation and denomination on the face, and a gum adhesive on the reverse side...
). This shape is probably only permitted by the high osmolarity of the water, permitting cell shapes that would be difficult, if not impossible, under other conditions.
Haloarchaea as Exophiles
Haloarchaea have been proposed as a kind of life that could live on MarsLife on Mars
Scientists have long speculated about the possibility of life on Mars owing to the planet's proximity and similarity to Earth. Fictional Martians have been a recurring feature of popular entertainment of the 20th and 21st centuries, but it remains an open question whether life currently exists on...
; since the Martian atmosphere has a pressure below the triple point
Triple point
In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases of that substance coexist in thermodynamic equilibrium...
of water, freshwater species would have no habitat on the Martian surface.