In taxonomy, the Halobacteriales are an order of the Halobacteria, found in water saturated or nearly saturated with salt. They are also called halophiles, though this name is also used for other organisms which live in somewhat less concentrated salt water. They are common in most environments where large amounts of salt, moisture, and organic material are available. Large blooms appear reddish, from the pigmentbacteriorhodopsin. This pigment is used to absorb light, which provides energy to create ATP. Halobacteria also possess a second pigment, halorhodopsin, which pumps in chloride ions in response to photons, creating a voltage gradient and assisting in the production of energy from light. The process is unrelated to other forms of photosynthesis involving electron transport; however, and halobacteria are incapable of fixing carbon from carbon dioxide. Halobacteria can exist in salty environments because although they are aerobes they have a separate and different way of creating energy through photosynthesis. Parts of the membranes of halobacteria are purplish in color. These parts conduct photosynthetic reactions with retinal pigment rather than chlorophyll. This allows them to create a proton gradient across the membrane of the cell which can be used to create ATP for their own use. Some species in this order are used as model organisms to study how some microorganisms can survive in hypersaline environments, understand cellular processes and to research their physiology.
Ecology
Habitats
Usually, Halobacteriales grow in aerobic and high salinity environments. Halobacteriales have been found in salt lakes, marine salterns, seawater, solar salts and salted food products. Mostly, members of the order Halobacteriales can be located in environments where concentrarion of salt exceeds 25%. However, they can also survive in environments with low concentrations of salt, between 1 and 3.5%. Studies show Halobacteriales can also be found in environments where sulfur reduction takes part as well as in salinity salterns,, seawater black smoker, coastal salt marshes and chimney structures. This results show Halobacteriales only need the enough amount of salt to prevent their lysis and thus can grow in environments with low salinity concentration.
