Archaebacteria-Halobacterium+salinarium

//Halobacterium salinarium//

Scientific Classification

 * **Scientific Name** || //Halobacterium salinarium// ||
 * **Kingdom** || Animalia ||
 * **Phylum** || Euryarchaeota ||
 * **Class** || Halobacteria ||
 * **Order** || Halobacteriales ||
 * **Family** || Halobacteriaceae ||

Introduction
Halobacterium salinarium is an archaea that acquires energy through photosynthesis. However it does not need chlorophyll or bacteriochlorophyll to do so. //Halobacterium salinarium// synthesizes the bacteriorhodopsin protein, which appears as a deep purple color under high-intensity lighting in a low-oxygen environment. It is motile, rod-shaped, lives in very salty environments. In fact, it is one of the few species that can live in highly saline environments. //Halobacterium salinarium// is found in salterns, hides, the Dead Sea, salted fish, salt pork, sausages, and other foods that contain a large amount of salt. Due to this archae's ability to survive at such high salt concentrations, it is classified as an extremeophile.



What does it look like?
General characteristics: Halobacterium colonies are often red in color due to the presence of carotenoids, but colonies producing bacteriorhodopsin are purple in color.
 * irregular rod-shaped cells
 * o.5-1.2 um X1.0-6.0 um in size
 * colonies are usually red or purple in colour
 * almost all are motile
 * Survive best in 12-15% salt concentration
 * chemoheterotrophic (feeding on organic material without photosynthesis)
 * can undergo photophosphorylation (The production of ATP using the energy of sunlight )
 * no spores
 * no resting stages

Cellular structure:

//Halobacterium salinarium// is single cellular and without a cell wall. The membrane is made up of a single lipid bilayer as well as a s-layer. This s-layer is made up of glycoprotein. There are other types of proteins on the cell surface. They all form a lattice shape in the membrane. The negative charge of the glycan chains is what makes the lattice stable in high-saline environments. The main source of chemical energy for //Halobacterium salinarium// is amino acids. Lastly, scientists have diiscovered that this type of archae undergoes gluconeogenesis to create sugars.


 * Other cellular characteristics:**
 * Lacks peptidoglycan
 * may form gas vacuoles



**Metabolism** Under conditions of high oxygen, these organisms carry out chemo-organotrophic respiration. However, when they are in a low oxygen environment with the presence of light, some //Halobacterium salinarium// can carry out a unique type of phototrophic metabolism. In other words, parts of the cell membrane become differentiated to form a purple membrane which contains a purple protein called bacteriorhodopsin. Bacteriorhodopsin contains retinal. Bacteriorhodopsin, on receiving light energy, pumps protons across the purple membrane. This then produces a proton-motive force that is used to initiate ATP synthesis. This system is the only known biological system in which light is used directly as a source of energy without the involvement of chlorophyll.

Fascinating Fact: Halobacterium salinarium is capable of using light as energy but without using chlorophyll.

Adaptations
Since these organisms are exposed to alot of UV radiation, they have evolved a sophisticated DNA repair mechanism. They are capable of repairing DNA very quickly and thus provide them with protection against UV radiation.

For buoyancy regulation, they produce gas vacuoles. Their membranes and proteins are well adapted ionic environments. Their ability to transport or accumulate inorganic K+ ions into the cell maintains the osmotic balance. When oxygen levels in the saline environment gets lower or disappear, they produce bacteriorhodopsin in the cell membrane. This bacteriorhodopsin changes the cell to a purple color and uses light energy to produce ATP for use.

**Habitat**
Since //Halobacterium salinarium// needs approximately 12-15 % salt concentration to live, they can be found in salt seas, salt lakes, rock salt, and saline soils. Sometimes, they are responsible for the red appearances of salt seas such as the Red Sea. Halobacteria can also be found on salted fish, salted hides, bacon, and sausage 




 * Resources **

Bacteria. ( 2010). In //Encyclopædia Britannica.// Retrieved November 15, 2010, from Encyclopædia Britannica Online School Edition: __ [] __

Ingleton, Paul, & Diana Sainsbury. (1981). //Introduction to bacteria: for students in the biological sciences//. Chichester: John Wiley & Sons.

Dyer, Betsey Dexter. (2003). //A field guide to bacteria.// N.Y.: Cornell University Press.

Heritage, J., E. G. V. Evans, & R. A. Killington. (1999). //Microbiology in action//. Cambridge, UK: Cambridge University Press.

Betsy, Tom, & Keogh, Jim. (2005). //Microbiology demystified.// New York: McGraw-Hill.

Postgate, J. R.. (2000). //Microbes and man//. 4th ed. New York: Cambridge University Press.


 * Image resources **

//Max Planck Institute of Biochemistry//. (2010). //Halobacterium salinarum//. Retrieved from []

Amy Shober. (2009). Halobacterium. Retrieved from []