''Haloferax mediterranei'' is a species of

archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...

in the family

Haloferacaceae ''Haloferacaceae'' is a family of halophilic, chemoorganotrophic or heterotrophic archaea within the order ''Haloferacales.'' The type genus of this family is ''Haloferax.'' Its biochemical characteristics are the same as the order ''Haloferacale ...

Discovery

''Haloferax mediterranei'' was discovered in 1983 in marine salterns in the village of

Santa Pola Santa Pola (Valencian and Spanish: ) is a coastal town located in the comarca of Baix Vinalopó in the Valencian Community, Spain, by the Mediterranean Sea. It has an area of and has a population of 30,000 inhabitants of whom 10,000 are resid ...

, Spain. The species was initially named ''Halobacterium mediterranei'', then renamed ''Haloferax mediterranei'' in 1986. Haloferax mediterranei is the fastest-growing known member of the Halobacteriales under optimal laboratory conditions, but it is relatively rare in the environment. The full genome of ''H. mediterranei'' was sequenced in 2012.

Metabolism and Growth Conditions

''Haloferax mediterranei'' is the fastest-growing archaeon in the Halobacteriales family, with generation times as low as 1.2 hours reported under optimal laboratory growth conditions. ''Haloferax mediterranei'' is able to use a variety of compounds as carbon and energy sources, and can accumulate materials to serve as a source of carbon and energy, as well as use organic and inorganic nitrogen sources. ''H. mediterranei'' is an extremely versatile microorganism that can anaerobically or aerobically, tolerate a wide range of salinities (between 10% and 32.5%), a wide range of pH values (between 5.75 and 8.75) and a wide range of temperatures (between 18 and 55^oC). It can also tolerate a variety of high metal concentrations, such as nickel, lithium, cobalt and arsenic, which are toxic to most organisms.

Morphology and Cell Division

''Haloferax mediterranei'' is an extremely pleomorphic organism, cells are usually flat disks. Like ''

Haloferax volcanii ''Haloferax volcanii'' is a species of organism in the genus ''Haloferax'' in the Archaea. Description and significance Microbiologist Benjamin Elazari Volcani first discovered ''Haloferax volcanii'', a self-named extremophile, in the 1930s. '' ...

'', it performs cell division through the formation of an

FtsZ FtsZ is a protein encoded by the ''ftsZ'' gene that assembles into a ring at the future site of bacterial cell division (also called the Z ring). FtsZ is a prokaryotic homologue of the eukaryotic protein tubulin. The initials FtsZ mean "Filamen ...

ring.

Biofilm and Exopolysaccharide formation

''Haloferax mediterranei'' produces a mucous exopolysaccharide matrix that accumulates as a top layer in liquid medium. This is a widespread strategy in the microbial world that helps

biofilms A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular po ...

adhere to surfaces, as well as protects cells from pH and temperature variations and radiation. These exopolysaccharides have been studied as potential emulsifiers for industry. The unshaken biofilms of ''H. mediterranei'' in liquid cultures rapidly rearrange into a honeycomb formation pattern upon exposure to air, a phenomenon that has yet to be fully elucidated.

PHA and PHB synthesis

''H. mediterranei'', when grown under phosphate limitation, produces

polyhydroxyalkanoates Polyhydroxyalkanoates or PHAs are polyesters produced in nature by numerous microorganisms, including through bacterial fermentation of sugars or lipids. When produced by bacteria they serve as both a source of energy and as a carbon store. M ...

, a type of biodegradable thermoplastic currently commercially produced using bacteria. It has been suggested that ''H. mediterranei'' is a good candidate for industrial production of biodegradable thermoplastics due to its fast growth, low contamination rates and ease of lysis. Deleting the genes responsible for exopolysaccharide synthesis results in a 20% increase in the amount of PHAs in the cell. Increasing the salt concentration of the media also increased the concentration of PHAs produced.

Gas Vesicles

Like some other members of the Halobacteriales group, notably '' Halobacterium salinarum'', ''Haloferax mediterranei'' produces gas vesicles, believed to act aiding buoyancy. The production of gas vesicles only occurs in high salt concentrations and once cells have reached stationary phase. By transforming 14 genes from the ''vac'' cluster of ''H. mediterranei'' into a gas-vesicle deficient archaeon '' H. volcanii'', researchers found that ''H. volcanii'' is able to produce functional gas vacuoles.

References

External links

* {{Taxonbar, from=Q25860197 Halobacteria Archaea described in 1983