linkedin post 2017-03-24 05:39:09

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BALANCE. "Viruses that cause chronic infection constitute a stable but little-recognized part of our metagenome: our virome. Ongoing immune responses hold these chronic viruses at bay while avoiding immunopathologic damage to persistently infected tissues. The immunologic imprint generated by these responses to our virome defines the normal immune system." https://lnkd.in/b9QHr8w View in LinkedIn
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linkedin post 2017-03-25 05:13:07

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FRAGMENT FROM NATURE. We have journeyed in this string of ideas from mosaicism the individual to division of labor and outsourcing of functionality. Now it continues with evolutionary bolt-ons that are inherited. The endosymbiotic origin of the nucleus, chloroplasts, mitochondria and other organelles may seem improbable. Symbiogenesis theory by Lynn Margulis (1967) proposed that mitochondria and chloroplasts arose by hereditable symbiosis in a huge saltation. Why did it stop there? Or did it? View in LinkedIn
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linkedin post 2017-03-25 05:18:00

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TRANSITION FROM OUTSIDE. "According to Keeling and Archibald, the usual way to distinguish organelles from endosymbionts is by their reduced genome sizes. As an endosymbiont evolves into an organelle, most of their genes are transferred to the host cell genome. The host cell and organelle need to develop a transport mechanism that enables transfer back of the protein products needed by the organelle but now manufactured by the cell." https://lnkd.in/dQewn-C View in LinkedIn
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linkedin post 2017-03-25 05:21:30

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THE KEY ENERGY JUMP. "The role of energy and the energetic constraints that prokaryotic cell organization placed on evolutionary innovation in cell history has recently come to bear on endosymbiotic theory. Only cells that possessed mitochondria had the bioenergetic means to attain eukaryotic cell complexity, which is why there are no true intermediates in the prokaryote-to-eukaryote transition." https://lnkd.in/d8-2n7b View in LinkedIn
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linkedin post 2017-03-25 05:24:51

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LOW MUTATION ACCUMULATION. "The most evolutionarily successful of heritable symbioses are those that gave rise to mitochondria and plastids, raising the question of why organelles have not been limiting baggage for eukaryotic hosts. Although numerous studies have documented excesses of deleterious mutations circulating within organelle genomes, these mutations are generally recent, remain at low frequencies, and do not become fixed within populations." https://lnkd.in/dcBwzRs View in LinkedIn
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linkedin post 2017-03-25 05:30:13

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GENETIC STREAMLINING. "Another difference between insect symbionts and organelles is that genomes of the latter encode little of their own machinery for self-replication and depend on import of needed gene products from the host. One consequence is that they typically have fewer genes and thus present a smaller mutational target. More importantly, organelle genes that are retained are subject to strong host-level selection, limiting their deterioration or selfish tendencies." https://lnkd.in/dcBwzRs View in LinkedIn
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linkedin post 2017-03-25 05:37:04

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DODGING THE RABBIT HOLE. "Highly reduced genomes of insect symbionts contain mostly genes involved with cell replication, transcription, and translation: Mutations in these genes will impact fitness of individual symbiont cells, where selfishness can originate. Thus, eukaryotic organelles may have escaped the symbiosis rabbit hole primarily because genes controlling symbiont replication are transferred to the host genome." https://lnkd.in/dcBwzRs View in LinkedIn
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