Currently, all living organisms are classified into three domains:. Originally, the two prokaryotic domains were considered only as a single kingdom Monera , however biochemical differences were discovered between the two groups which warranted their reclassification into separate domains.
Three Domains of Life. Brent Cornell. Cell Introduction 2. Cell Structure 3. Membrane Structure 4. Membrane Transport 5. Origin of Cells 6. Cell Division 2: Molecular Biology 1. Metabolic Molecules 2. Water 3. Microbiology and Molecular Biology Reviews 61 , — Doolittle, W. Pattern pluralism and the Tree of Life hypothesis. PNAS , — Embley, T.
Eukaryotic evolution, changes and challenges. Nature , — Esser, C. A genome phylogeny for mitochondria among alpha-proteobacteria and a predominantly eubacterial ancestry of yeast nuclear genes. Molecular Biology and Evolution 21 , — Gogarten, J.
PNAS 86 , — Koonin, E. The ancient Virus World and evolution of cells. Biology Direct 19 , 29 Genomics of bacteria and archaea: The emerging dynamic view of the prokaryotic world.
Nucleic Acids Research 36 , — Kristensen, D. New dimensions of the virus world discovered through metagenomics. Trends in Microbiology 18 , 11—19 Martin, W. Introns and the origin of nucleus-cytosol compartmentation. Nature , 41—45 Moreira, D. Ten reasons to exclude viruses from the tree of life. Nature Reviews Microbiology 7 , — Pal, C. Adaptive evolution of bacterial metabolic networks by horizontal gene transfer. Nature Genetics 37 , — Puigbo, P. Search for a Tree of Life in the thicket of the phylogenetic forest.
Journal of Biology 8 , 59 Raoult, D. Redefining viruses: Lessons from mimivirus. Nature Reviews Microbiology 6 , — doi Woese, C. Towards a natural system of organisms: Proposal for the domains Archaea, Bacteria, and Eucarya.
PNAS 87 , — What Is a Cell? Eukaryotic Cells. Cell Energy and Cell Functions. Photosynthetic Cells. Cell Metabolism. The Origin of Mitochondria. Mitochondrial Fusion and Division. The Origin of Plastids. The Origins of Viruses. Discovery of the Giant Mimivirus. Volvox, Chlamydomonas, and the Evolution of Multicellularity. Yeast Fermentation and the Making of Beer and Wine. Dynamic Adaptation of Nutrient Utilization in Humans. Nutrient Utilization in Humans: Metabolism Pathways.
An Evolutionary Perspective on Amino Acids. Mitochondria and the Immune Response. Stem Cells in Plants and Animals. Promising Biofuel Resources: Lignocellulose and Algae. The Discovery of Lysosomes and Autophagy. The microbes in the domain Archaea look like bacteria, but are different in a few essential ways. They often live in extreme places, like in the cold deep sea, hot geysers, or acidic volcanoes.
The third domain, Eukarya, differs greatly from the other two. The cells in the species of this domain, therefore, have a nucleus. Others propose that the domains Archaea and Eukarya emerged from a common archaeal-eukaryotic ancestor that itself emerged from a member of the domain Bacteria. Some of the evidence behind this hypothesis is based on a "superphylum" of bacteria called PVC, members of which share some characteristics with both archaea and eukaryotes. There is growing evidence that eukaryotes may have originated within a subset of archaea.
In any event, it is accepted today that there are three distinct domains of organisms in nature: Bacteria, Archaea , and Eukarya. A description of the three domains follows.
There is a "superphylum" of bacteria called PVC, referring to the three members of that superphylum: the Planctomycetes, the Verrucomicrobia, and the Chlamydiae. Some of these bacteria show cell compartmentalization wherein membranes surround portions of the cell interior, such as groups of ribosomes or DNA, similar to eukaryotic cells.
Some divide by budding or contain sterols in their membranes, again similar to eukaryotes. Some lack peptidoglycan, similar to eukaryotes and archaea. It has been surmised that these bacteria migh be an intermediate step between an ancestor that emerged from a bacterium domain Bacteria and an archael-eukaryotic ancestor prior to its split into the domains Archaea and Eukarya.
Archaea often live in extreme environments and include methanogens, extreme halophiles, and hyperthermophiles. One reason for this is that the ether-containing linkages in the Archaea membranes is more stabile than the ester-containing linkages in the Bacteria and Eukarya and are better able to withstand higher temperatures and stronger acid concentrations.
Bacteria also known as eubacteria or "true bacteria" are prokaryotic cells that are common in human daily life, encounter many more times than the archaebacteria.
Eubacteria can be found almost everywhere and kill thousands upon thousands of people each year, but also serve as antibiotics producers and food digesters in our stomachs.
The Bacteria possess the following characteristics:. Bacteria include mycoplasmas, cyanobacteria, Gram-positive bacteria, and Gram-negative bacteria. The Eukarya also spelled Eucarya possess the following characteristics:. The Eukarya are subdivided into the following four kingdoms:. It used to be thought that the changes that allow microorganisms to adapt to new environments or alter their virulence capabilities was a relatively slow process occurring within an organism primarily through mutations, chromosomal rearrangements, gene deletions and gene duplications.
0コメント