Haloarcula

In taxonomy, Haloarcula is a genus of the Halobacteriaceae. Haloarcula species are extreme halophilic archaea. They are distinguished from other genera in the Halobacteriaceae family by the presence of specific derivatives of TGD-2 polar lipids. Currently, seven recognized species are in the genus: H. vallismortis, H. marismortui, H. hispanica, H. japonica, H. argentinensis, H. mukohataei, and H. quadrata. H. quadrata was first isolated when researchers were attempting to culture Haloquadratum walsbyi, a haloarchaeon that was thought to be unculturable until 2004. H. quadrata has predominantly flat, square-shaped, somewhat pleomorphic cells. H. marismortui has one of the only two prokaryotic large ribosomal subunits which have so far been crystallized. The other one is Deinococcus radiodurans. Haloarcula species grow optimally at 40–45 °C. Growth appears in sheets of up to 65 cells often in the shape of a square or triangle. Haloarcula species are found in neutral saline environments such as salt lakes, marine salterns, and saline soils. Like other members of the Halobacteriaceae family, Haloarcula requires at least 1.5 M NaCl for growth, but grow optimally in 2.0 to 4.5 M NaCl.