Halobacterium salinarum
Anthony Gonzalez

Halobacteria are halophilic microorganisms, which means they grow in extremely high salinity environments. This archaeon can act as a good model for some aspects of eukaryotic biology, such as DNA replication, transcription, and translation. Comparing a halophile genome to that of other prokaryotes should give insight into microbial adaptation to extreme conditions.

Of the archaea, Halobacteria are viewed as being involved in the most lateral genetics (gene transfer between domains) and a proof that this transfer does take place.

Halobacterium species are rod shaped and enveloped by a single lipid bilayer membrane surrounded by an S-layer made from the cell-surface glycoprotein. Halobacteria grow on amino acids in aerobic conditions. Although Halobacterium salinarum contains genes for glucose degradation as well as genes for enzymes of a fatty acid oxidation pathway, it does not seem able to use these as energy sources. Even though the cytoplasm retains an osmotic equilibrium with the hyper saline environment, the cell maintains a high potassium concentration. It does this by using many active transporters.

Halobacteria can be found in highly saline lakes such as the Great Salt Lake, the Dead Sea, and Lake Magadi. Halobacterium can be identified in bodies of water by the light-detecting pigment bacteriorhodopsin, which not only provides the archaeon with chemical energy, but gives it a reddish hue as well. An optimal temperature for growth has been observed at 37oC.

On an interesting note, however, Halobacteria are a candidate for a life form present on Mars. One of the problems associated with the survival on Mars is the destructive ultraviolet light. Halobacteria have an advantage here. These microorganisms develop a thin crust of salt that can moderate some of the ultraviolet light. Sodium chloride is the most common salt and chloride salts are opaque to short-wave ultraviolet. Their photosynthetic pigment, bacteriorhodopsin, is actually correspondent to the longer wavelength ultraviolet. The obstacle Halobacteria would need to overcome is being able to grow at a low temperature during a presumably short time span when a pool of water could be liquid.

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.


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