Endosymbionts and mitochondrial origins

Woese, Carl R.

doi:10.1007/bf01751802

Cited by 54 publications

(36 citation statements)

References 13 publications

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“…Based on ribosomal RNA taxonomy [105], we know today that symbiogenesis was responsible for two of the most important events in all of evolutionary history: (a) Incorporation of an alpha-proteobacterium as the mitochondrion in the ancestor of all eukaryotic cells [106]. (b) Incorporation of a cyanobacterium as the plastid in the ancestor of photosynthetic eukaryotes [107].…”

Section: Symbiogenesismentioning

confidence: 99%

How life changes itself: The Read–Write (RW) genome

Shapiro

2013

Physics of Life Reviews

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The genome has traditionally been treated as a Read-Only Memory (ROM) subject to change by copying errors and accidents. In this review, I propose that we need to change that perspective and understand the genome as an intricately formatted Read-Write (RW) data storage system constantly subject to cellular modifications and inscriptions. Cells operate under changing conditions and are continually modifying themselves by genome inscriptions. These inscriptions occur over three distinct time-scales (cell reproduction, multicellular development and evolutionary change) and involve a variety of different processes at each time scale (forming nucleoprotein complexes, epigenetic formatting and changes in DNA sequence structure). Research dating back to the 1930s has shown that genetic change is the result of cell-mediated processes, not simply accidents or damage to the DNA. This cell-active view of genome change applies to all scales of DNA sequence variation, from point mutations to large-scale genome rearrangements and whole genome duplications (WGDs). This conceptual change to active cell inscriptions controlling RW genome functions has profound implications for all areas of the life sciences.

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Section: Symbiogenesismentioning

confidence: 99%

How life changes itself: The Read–Write (RW) genome

Shapiro

2013

Physics of Life Reviews

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“…Mitochondria evolved from endosymbiotic purple nonsulphur bacteria (a-proteobacteria; John & Whatley 1975, 1977Andersson et al 2003), but precisely how has been unclear. The nature of the host and the initial selective advantage of intracellular enslavement have been debated (Martin & Mü ller 1998;Cavalier-Smith 2002a;Andersson et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Origin of mitochondria by intracellular enslavement of a photosynthetic purple bacterium

2006

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Mitochondria originated by permanent enslavement of purple non-sulphur bacteria. These endosymbionts became organelles through the origin of complex protein-import machinery and insertion into their inner membranes of protein carriers for extracting energy for the host. A chicken-and-egg problem exists: selective advantages for evolving import machinery were absent until inner membrane carriers were present, but this very machinery is now required for carrier insertion. I argue here that this problem was probably circumvented by conversion of the symbiont protein-export machinery into protein-import machinery, in three phases. I suggest that the first carrier entered the periplasmic space via pre-existing b-barrel proteins in the bacterial outer membrane that later became Tom40, and inserted into the inner membrane probably helped by a pre-existing inner membrane protein, thereby immediately providing the protoeukaryote host with photosynthesate. This would have created a powerful selective advantage for evolving more efficient carrier import by inserting Tom70 receptors. Massive gene transfer to the nucleus inevitably occurred by mutation pressure. Finally, pressure from harmful, non-selected gene transfer to the nucleus probably caused evolution of the presequence mechanism, and photosynthesis was lost.

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“…The presence of this eubacterial endosymbiont allowed the host to colonize aerobic environments. A variety of mechanisms have been suggested as to why this should be so; the most popular, and one that features in a variety of different formulations for mitochondrial origins (Woese 1977;Martin & Mü ller 1998;Vellai et al 1998;Kurland & Andersson 2000), being the removal of cytosolic oxygen by the endosymbionts' respiratory activity. The feasibility of this idea, at least as a mechanism, is supported by a modern analogue among contemporary ciliate protozoa.…”

Section: Introductionmentioning

confidence: 99%

Multiple secondary origins of the anaerobic lifestyle in eukaryotes

Embley

2006

Phil. Trans. R. Soc. B

111

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Classical ideas for early eukaryotic evolution often posited a period of anaerobic evolution producing a nucleated phagocytic cell to engulf the mitochondrial endosymbiont, whose presence allowed the host to colonize emerging aerobic environments. This idea was given credence by the existence of contemporary anaerobic eukaryotes that were thought to primitively lack mitochondria, thus providing examples of the type of host cell needed. However, the groups key to this hypothesis have now been shown to contain previously overlooked mitochondrial homologues called hydrogenosomes or mitosomes; organelles that share common ancestry with mitochondria but which do not carry out aerobic respiration. Mapping these data on the unfolding eukaryotic tree reveals that secondary adaptation to anaerobic habitats is a reoccurring theme among eukaryotes. The apparent ubiquity of mitochondrial homologues bears testament to the importance of the mitochondrial endosymbiosis, perhaps as a founding event, in eukaryotic evolution. Comparative study of different mitochondrial homologues is needed to determine their fundamental importance for contemporary eukaryotic cells.

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Endosymbionts and mitochondrial origins

Cited by 54 publications

References 13 publications

How life changes itself: The Read–Write (RW) genome

How life changes itself: The Read–Write (RW) genome

Origin of mitochondria by intracellular enslavement of a photosynthetic purple bacterium

Multiple secondary origins of the anaerobic lifestyle in eukaryotes

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