Archaea are genetically distinct from bacteria and eukaryotes, but are poorly understood: many of the genes that Archaea encode are of unknown function.
Archaea show high levels of horizontal gene transfer between lineages.
These gene transfers are identified by sequencing the DNA of various Archaea species; through the similarities and differences of the DNA of the different types of Archaea it is determined if the gene was perfectly transferred or from a common ancestor.
How genetic material can move from one Archaea to another is poorly understood.
As well Archaea can be infected by viruses.
Archaea are distinct from bacteria and eukaryotes, but genetic material can be transferred between them and between Archaea themselves.
The Archaea constitute a domain of single-celled microorganisms.
Archaea are genetically distinct from bacteria and eukaryotes, with up to 15% of the proteins encoded by any one archaeal genome being unique to the domain, even though most of these unique genes have no known function.
The proteins that archaea, bacteria and eukaryotes share form a common core of cell function, relating mostly to transcription, translation, and nucleotide metabolism.
Transcription and translation in archaea resemble these processes in eukaryotes more than in bacteria, with the archaean RNA polymerase and ribosomes being very close to their equivalents in eukaryotes.
Although archaea only have one type of RNA polymerase, its structure and function in transcription seems to be close to that of the eukaryotic RNA polymerase II, with similar protein assemblies (the general transcription factors) directing the binding of the RNA polymerase to a gene's promoter.
Transcription and translation in archaea resemble these processes in eukaryotes more than in bacteria.
Most of the metabolic pathways, which comprise the majority of an organism’s genes, are common between Archaea and Bacteria, while most genes involved in genome expression are common between Archaea and Eukarya.
Archaea and Gram-positive bacteria also share conserved indels in a number of important proteins, such as Hsp70 and glutamine synthetase I.R.S.
Gupta has proposed that the Archaea evolved from Gram-positive bacteria in response to antibiotic selection pressure.
This is suggested by the observation that archaea are resistant to a wide variety of antibiotics that are primarily produced by Gram-positive bacteria, and that these antibiotics primarily act on the genes that distinguish Archaea from Bacteria.
His proposal is that the selective pressure towards resistance generated by the Gram-positive antibiotics was eventually sufficient to cause extensive changes in many of the antibiotics' target genes, and that these strains represented the common ancestors of present-day Archaea.
Most of the metabolic pathways, which comprise the majority of an organism’s genes, are common between Archaea and Bacteria.
The evolutionary relationship between archaea and eukaryotes remains unclear.
The leading hypothesis is that the ancestor of the eukaryotes diverged early from the Archaea, and that eukaryotes arose through fusion of an archaean and eubacterium, which became the nucleus and cytoplasm.
This explains various genetic similarities but runs into difficulties when it comes to explaining cell structure.Despite this visual similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely-related to those of eukaryotes, notably the enzymes involved in transcription and translation.Archaea exhibit a great variety of chemical reactions in their metabolism and use many sources of energy.
Some archaea obtain energy from inorganic compounds such as sulfur or ammonia (they are lithotrophs).
Archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes than prokaryotes.