Haloferax

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A Microbial Biorealm page on the genus Haloferax

Cells of Halferax volcanii. Image from Prof. Moshe Mevarech, Tel Aviv University.

Classification

Higher order taxa:

Archaea, Euryarchaeota, Halobacteria, Halobacteriales, Halobacteriaceae, Haloferax

NCBI: Taxonomy Genome

Description and Significance

Haloferax volcanii is a species of halophile which exists in extreme saline environments. Recently an isolate of this species was studied by researchers at University of California-Berkeley as part of a project on the survival of haloarchaea on Mars. Like other halophiles, Haloferax volcanii has been isolated in high-saline environments, most commonly the Dead Sea, the Great Salt Lake, and oceanic environments with high NaCl concentrates.

Genome Structure

Haloferax volcanii's genome has been officially completely sequenced, however it is not yet available in full in annotated form. The molecular biology of H. volcanii has been extensively studied for the last decade in order to discover more about DNA replication, DNA repair and RNA synthesis. The archaeal proteins used in these processes are extremely similar to Eukaryotic proteins and so are studied primarily as a model system for these organisms. Haloferax volcanii undergoes prolific horizontal gene transfer both with Archaea and, to a lesser extent, bacteria.

Cell Structure and Metabolism

Reproductive cycle of Haloferax volcanii. Image from Prof. Moshe Mevarech, Tel Aviv University.

Reproduction among Haloferax volcanii occurs when two cells fuse, establish cytoplasmic bridges, and exchange genetic information, forming two daughter cells. While this practice may sound similar to the mating habits of eukaryotes, Haloferax volcanii appears to be indiscriminatory when it comes to choosing prospective reproductive partner cells. They appear to be capable of fusing with the cells of any species within the Haloferax genus; their methods of specificity are virtually unknown. Haloferax volcanii processes carbohydrates for energy. Their cell wall S-layer, like all halobacteria, is made up of a glycoprotein. And in keeping with their halophilic categorization, Haloferax volcanii cells contain proteins to allow them to maintain balance between the cell material and the hypersaline environment.

Ecology

Oceanic ice flow, typical high-salinity environment of organisms such as Haloferax volcanii. Image from UC-Berkeley (by D.N. Thomas).

Isolates of Haloferax volcanii are commonly found in high-salinity aquatic environments, such as the Dead Sea. Their precise role in the ecosystem is uncertain, but the proteins contained within these organisms potentially serve many practical purposes. Because of their ability to maintain homeostasis in spite of the salt around them, Haloferax volcanii could be an important player in advancements in biotechnology. As it is likely that Haloferax volcanii and comparable species are ranked among the earliest living organisms, they also provide information related to genetics and evolution.

References

Allers, Thorston. Research Interests. School of Biology, University of Nottingham.

Chu, Huitung et al. Exobiology: The Survival Ability of Halophiles Under Martian Conditions. University of California-Berkeley Earth and Planetary Science Department.

DasSarma, Shiladitya et al. Halophiles. Halobacterium Genome Project, University of Maryland.

Mevarech, Moshe. The mechanism of the natural genetic exchange of Haloferax volcanii. Molecular Microbiology and Biotechnology Department, Tel Aviv University.

Redkar, Rajendra J. et al. The Haloferax volcanii Genome Project. Microbial Genome Program Section.