Hyperthermophilic Archaea

Boonsri Jongsareejit


Archaea is considered to have the slowest evolution among all organisms. Studies on the genome structure of archaea indicate that it is similar in size to that of bacteria. However, most protein produced in archaea have eukaryotic features, which indicates a close relationship between archaea and eukarya in the course of evolution. The archaea and eukarya likely had a common ancestor not shared by the bacteria, and the first organisms to have diverged from the eukarya/archaea lineage were hyperthermophiles. Hyperthermophilic organisms therefore appear more closely related than all other organisms to the ancestor of all extant life, having evolved when the earth was much hotter than it is at present. Hyperthermophilic archaea can be divided into three groups by sulfur dependency; sulfur dependent, sulphate reducing genus and thermophilic methanogens. From Genome structure of hyperthermophilic archaea revealed that the small size genomes of hyperthermophiles may define the lower limit for their genetic capacity. Chromosomes of hyperthermophiles appear to be densely packed with genes, most of which are required for essential functions. This suggests that the earliest life forms may have had small genomes. Furthermore, the importance of archaea genomics is implicit in a universal phylogenetic tree; certain complex eukaryotic functions can be effectively studied in simpler archaeal systems, molecular structures can be inferred from thermostable archaeal proteins, and the functional essence of an enzyme or system can be revealed by a broader comparative analysis.

Therefore, analysis of the archaea genome structure will provide us with a useful insight. The entire archaeal genome sequence of archaea would be useful to understand about the archaea themselves, thermophile, their relationship to the eukaryotic cell, the origin of the three primary lines of descent, and the nature of the most recent universal ancestor.

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