Genus Halobacterium

Genus Halobacterium

The organism Halobacterium is a "salt-loving" organism which is classified in the Domain Archaea. These organisms require an environment which contains high concentrations of salt, which would dehydrate and kill most other cells. Halobacteria reproduce and grow best in higher temperature waters and can most often be found in the Great Salt Lake, the Dead Sea, Lake Magadi, and any other waters with high salt concentration. According to Shiladitya DasSarma, "Many have the ability to grow in the absence of oxygen via dissimilatory nitrate reduction and denitrification, fermentation of different sugars, breakdown of arginine, and use of light energy mediated by retinal pigments" (DasSarma & Arora, 2001). Halobacteria cannot survive in any water conditions in which the salt concentration becomes more than five times lower than the salt concentration of normal seawater. These bacteria require the use of aerobic respiration in order to produce and use energy. Although, due to the fact that at many times warm salty water has a low amount of oxygen, Halobacteria often go through shortages in the amount of ATP that these organisms synthesize due to them not being able to extract enough oxygen from the waters. Sunlight is then Halobacterias last option for producing enough ATP in order to survive. These organisms capture sunlight by patches of purple protein called bacteriorhodopsin. In order for this to occur the pigment molecules puncture through the membrane so that way when sunlight hits the bacteriorhodopsin a series of reactions occurs where a hydrogen ion is pumped from the inside of the cell to the outside. Lastly, for energy to be produced for the synthesis of ATP the hydrogen ions must be able to flow back into the cell. According to Turner, "Gas vesicles are hollow proteinaceous structures surrounding a gas filled space. The function of gas vesicles for Halobacteria, organisms whose primary metabolism is aerobic and that live in concentrated brines in which the solubility of molecular oxygen is low (especially at high temperatures), is to enable the cells to float to the more oxygenated surface layers" (Turner (2010). Halobacteria also produce extremely large amounts of red-orange carotenoids which are said to be necessary in order to stimulate an active photorepair system in help repair thymine dimers resulting from ultra violet light. Halobacteria are very distinct organisms which have been shown to be able to adapt, reproduce, grow, and survive in extreme environments.

References

DasSarma S, Arora P: Halophiles. In Encyclopedia of Life Sciences Volume 8. Nature Publishing Group; 2002:458-466.

Turner, R. L., Jr., G. K., & Small Jr., J. W. (2010).