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An endosymbiont or endobiont [1] is an organism that lives within the body or cells of another organism. Typically the two organisms are in a mutualistic relationship. Examples are nitrogen-fixing bacteria (called rhizobia ), which live in the root nodules of legumes , single-cell algae inside reef-building corals , and bacterial endosymbionts ...
The original theory by Lynn Margulis proposed an additional preliminary merger, but this is poorly supported and not now generally believed. [1] Symbiogenesis (endosymbiotic theory, or serial endosymbiotic theory [2]) is the leading evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms. [3]
I greatly admire Lynn Margulis's sheer courage and stamina in sticking by the endosymbiosis theory, and carrying it through from being an unorthodoxy to an orthodoxy. I'm referring to the theory that the eukaryotic cell is a symbiotic union of primitive prokaryotic cells.
The theory of endosymbiosis, as known as symbiogenesis, provides an explanation for the evolution of eukaryotic organisms. According to the theory of endosymbiosis for the origin of eukaryotic cells, scientists believe that eukaryotes originated from the relationship between two or more prokaryotic cells approximately 2.7 billion years ago.
Because the nucleomorph lies between two sets of membranes, nucleomorphs support the endosymbiotic theory and are evidence that the plastids containing them are complex plastids. Having two sets of membranes indicate that the plastid, a prokaryote, was engulfed by a eukaryote, an alga, which was then engulfed by another eukaryote, the host cell ...
According to the endosymbiont theory, mitochondria and chloroplasts were once free-living organisms that were each taken up by a eukaryotic cell. [11] Over time, mitochondria and chloroplasts formed a symbiotic relationship with their eukaryotic hosts. Although the transfer of a number of genes from these organelles to the nucleus prevents them ...
As the endosymbiont adapts to the host's lifestyle, the endosymbiont changes dramatically. There is a drastic reduction in its genome size, as many genes are lost during the process of metabolism , and DNA repair and recombination, while important genes participating in the DNA-to-RNA transcription , protein translation and DNA/RNA replication ...
The hydrogen hypothesis is a model proposed by William F. Martin and Miklós Müller in 1998 that describes a possible way in which the mitochondrion arose as an endosymbiont within a prokaryotic host in the archaea, giving rise to a symbiotic association of two cells from which the first eukaryotic cell could have arisen (symbiogenesis).