|Euryarchaeota||Carl Woese and colleagues divided the Archaea into two “kingdoms,” Euryarchaeota and Crenarchaeota, in 1990.1||Includes halophiles and methanogens.|
Members of the order Thermoplasmateles
are acidophiles and thermophiles.
|TACK||Scientists proposed the TACK name in 2011 to encompass the phyla Thaumarchaeota, Aigarchaeota, Crenarchaeota,|
and Korarchaeota;2 more phyla have been added since.
|Includes thermophiles. Thaumarchaeota participate in nitrogen cycling. Some|
are also methanogens.
|DPANN||The first phylum named was Nanoarchaeota, in 2002, for a tiny deep-sea vent organism that didn’t fit into Euryarchaeota or Crenarchaeota.3 In 2013, researchers proposed linking it with the taxa Diapherotrites, Parvarchaeota, Aenigmarchaeota,|
and Nanohaloarchaeota.4 New phyla have been added since.
|At least some are small in size, with small genomes lacking genes for key proteins in metabolism and other processes. Some may rely on a symbiont or host organism to survive.|
|Asgard||The first discovered were Lokiarchaeota, which were initially thought to be members of the TACK superphylum.5 The group now contains a handful of phyla, all named for Norse deities.6||Genomes encode several proteins|
similar to those found in eukaryotes.
|1. PNAS, 87:4576-79, 1990; 2. Trends Microbiol, 19:580-87, 2011; 3. Nature, 417:63-67, 2002; 4. Nature, 499:431-37, 2013; 5. Nature, 521:173-79, 2015; 6. Nature, 541:353-58, 2017|
See “Older Sisters”
Bacteria typically possess one chromosome with one origin of replication. Eukaryotes have multiple, paired chromosomes with numerous origins on each. Archaea straddle the divide: while they typically have one main chromosome, it often replicates from multiple origins.
Archaea can possess megaplasmids—hundreds of kilobases in size—that contain crucial genes. Some species are haploid like bacteria but many exhibit varying degrees of polyploidy. Many archaea use histones, as eukaryotes do, to organize their genomes, but some rely on alternative Alba proteins.
Modes of Cell Division
Some archaea divide via a mechanism similar to that of bacteria, using the cytoskeleton-like protein FtsZ to form a ring at the eventual division site (left). Others use homologs of eukaryote proteins, such as ESCRTs, to help separate daughter cells (right). Still others lack both of those systems, so they presumably have a distinct, as-yet-unknown mechanism, possibly relying on a form of actin.
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