archaea

Examples of archaea in the following topics:

• Chromosomes and DNA Replication in the Archaea

  • Smaller independent pieces of DNA, called plasmids, are also found in archaea.
  • Archaea typically have a single circular chromosome.
  • This process in Archaea appears to be similar to both bacterial and eukaryotic systems.
  • The DNA replication system in Archaea, similar to all systems, requires a free 3'OH group before synthesis is initiated.
  • The primase used by archaea is a highly derived version of the RNA recognition motif (RRM).

• Energy Conservation and Autotrophy in Archaea

  • Archaea can use a number of different mechanisms to get nutrients and energy.
  • Archaea exhibit a variety of chemical reactions in their metabolism and use many sources of energy.
  • These reactions are common in gut-dwelling archaea.
  • Phototrophic archaea use sunlight as a source of energy; however, oxygen–generating photosynthesis does not occur in any archaea.
  • Archaea can live in extreme environments and live off autotrophic sources.

• Shared Features of Archaea and Eukaryotes

  • The evolutionary relationship between archaea and eukaryotes remains unclear.
  • 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).
  • Phylogenetic tree showing the relationship between the Archaea and other domains of life.
  • Eukaryotes are colored red, archaea green and bacteria blue.

• Shared Features of Bacteria and Archaea

  • Most of the metabolic pathways, which comprise the majority of an organism's genes, are common between Archaea and 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.
  • 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.
  • Describe the evidence for the evolution of the Archaea from Bacteria

• Control of Transcription in Archaea

  • Transcription and translation in archaea resemble these processes in eukaryotes more than in bacteria.
  • The Archaea constitute a domain of single-celled microorganisms.
  • 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.
  • Compare the archaea with bacteria and eukaryotes in terms of their general mechanisms of gene expression

• Viruses of Archaea

  • Most viruses infecting Archaea are double-stranded DNA viruses that are unrelated to any other form of virus.
  • The second single stranded DNA virus infecting Archaea is Aeropyrum coil-shaped virus (ACV).
  • A virus infecting archaea was first described in 1974.
  • Two groups of single-stranded DNA viruses that infect archaea have been recently isolated.
  • Species of the genus Salterprovirus infect halophilic archaea species of the Euryarchaeota.

• Habitats and Energy Metabolism of Crenarchaeota

  • The Crenarchaeota are Archaea that have been classified as either a phylum of the Archaea kingdom, or in a kingdom of its own.
  • Extremophile archaea are members of four main physiological groups.
  • Other archaea exist in very acidic or alkaline conditions.
  • These reactions are common in gut-dwelling archaea.
  • No known archaea carry out photosynthesis.

• Gene Transfer in Archaea

  • Archaea are distinct from bacteria and eukaryotes, but genetic material can be transferred between them and between Archaea themselves.
  • 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.
  • How genetic material can move from one Archaea to another is poorly understood.
  • As well Archaea can be infected by viruses.

• Archaeal Gene Regulation

  • Archaea usually have a single circular chromosome, the size of which may be as great as 5,751,492 base pairs in Methanosarcina acetivorans, the largest known archaean genome.
  • Smaller independent pieces of DNA, called plasmids, are also found in archaea.
  • Archaea can be infected by double-stranded DNA viruses that are unrelated to any other form of virus and have a variety of unusual shapes, including bottles, hooked rods, or teardrops.
  • Two groups of single-stranded DNA viruses that infect archaea have been recently isolated.
  • The proteins that archaea, bacteria, and eukaryotes share form a common core of cell function, relating mostly to transcription, translation, and nucleotide metabolism.

• Cell Walls of Archaea

  • Archaea builds the same structures as other organisms, but they build them from different chemical components.
  • Likewise, archaea do not produce walls of cellulose (as do plants) or chitin (as do fungi).
  • The most striking chemical differences between Archaea and other living things lie in their cell membrane.
  • State the similarities between the cell walls of archaea and bacteria