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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Archaea | 7/9 | https://en.wikipedia.org/wiki/Archaea | reference | science, encyclopedia | 2026-05-05T07:15:06.056512+00:00 | kb-cron |
Archaea reproduce asexually by binary or multiple fission, fragmentation, or budding; mitosis and meiosis do not occur, so if a species of archaea exists in more than one form, all have the same genetic material. Cell division is controlled in a cell cycle; after the cell's chromosome is replicated and the two daughter chromosomes separate, the cell divides. In the genus Sulfolobus, the cycle has characteristics that are similar to both bacterial and eukaryotic systems. The chromosomes replicate from multiple starting points (origins of replication) using DNA polymerases that resemble the equivalent eukaryotic enzymes. In Methanobacteriati the cell division protein FtsZ, which forms a contracting ring around the cell, and the components of the septum that is constructed across the center of the cell, are similar to their bacterial equivalents. In cren- and thaumarchaea, the cell division machinery Cdv fulfills a similar role. This machinery is related to the eukaryotic ESCRT-III machinery which, while best known for its role in cell sorting, also has been seen to fulfill a role in separation between divided cell, suggesting an ancestral role in cell division. Both bacteria and eukaryotes, but not archaea, make spores. Some species of Haloarchaea undergo phenotypic switching and grow as several different cell types, including thick-walled structures that are resistant to osmotic shock and allow the archaea to survive in water at low salt concentrations, but these are not reproductive structures and may instead help them reach new habitats.
== Behavior ==
=== Communication === Quorum sensing was originally thought to not exist in Archaea, but recent studies have shown evidence of some species being able to perform cross-talk through quorum sensing. Other studies have shown syntrophic interactions between archaea and bacteria during biofilm growth. Although research is limited in archaeal quorum sensing, some studies have uncovered LuxR proteins in archaeal species, displaying similarities with bacteria LuxR, and ultimately allowing for the detection of small molecules that are used in high density communication. Similarly to bacteria, Archaea LuxR solos have shown to bind to AHLs (lactones) and non-AHLs ligans, which is a large part in performing intraspecies, interspecies, and interkingdom communication through quorum sensing.
=== Biofilms === Archaea are known to form biofilms, a common strategy among microorganisms. Quorum sensing is thought to play a role in Archaeal biofilm formation, but less is known about Archaeal quorum sensing than Bacterial quorum sensing. Some Archaea have been observed to form biofilms when the pH is a specific value, without necessarily relying on quorum sensing for instance. These biofilms are sessile communities of micro-organisms (they can contain multiple different species) that produce extracellular polymeric substances, which are used to create a matrix, within which the micro-organisms can grow. Biofilms are beneficial as they: protect organisms from abiotic stresses; facilitate horizontal gene transfer; and enable syntropy to take place. Biofilm formation has a number of stages: attachment; micro-colony formation; maturation; and dispersal. During the attachment phase the Archaea are reversibly attached to a surface by type-4 pili and archaella. Some Archaea possess other structures involved in attachment such as hami; fimbriae; or cannulae. During the micro colony phase, the extracellular polymeric substance matrix is produced, and numerous archaea have been observed to produce pills and nanowires between cells. During the maturation phase the matrix takes on a sophisticated architecture, such as including pathways for waste to exit the biofilms. Different archaea have been observed to produce biofilms with different architectures. Finally, dispersal can take place, where cells begin to leave the biofilm, this process has been observed in Archaea but the mechanisms behind it are not understood.
== Ecology ==
=== Habitats ===