Evolution of flagella
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The evolution of flagella is of great interest to
Eukaryotic flagellum
There are two competing groups of models for the evolutionary origin of the eukaryotic flagellum (referred to as cilium below to distinguish it from its bacterial counterpart). Recent studies on the microtubule organizing center suggest that the most recent ancestor of all eukaryotes already had a complex flagellar apparatus.[1]
Endogenous, autogenous and direct filiation models
These models argue that
An intermediate stage between spindle and cilium would be a non-swimming appendage made of microtubules with a function subject to natural selection, such as increasing surface area, helping the protozoan remain suspended in water, increasing the chances of bumping into bacteria to eat, or serving as a stalk attaching the cell to a solid substrate.
Regarding the origin of the individual protein components, a paper on the evolution of dyneins
Symbiotic/endosymbiotic/exogenous models
These models argue that the cilium evolved from a
The modern version of the hypothesis was first proposed by
One primary point in favor of the symbiotic hypothesis was that there are eukaryotes that use symbiotic spirochetes as their
Margulis' hypothesis suggests that an archaea acquired
Bacterial flagellum
There is good evidence that the bacterial flagellum includes and might even be based on a
All currently known nonflagellar Type III transport systems serve the function of exporting (injecting)
However, the true relationship could be the reverse: recent phylogenetic research strongly suggests the type three secretory system evolved from the flagellum through a series of gene deletions.[7]
Eubacterial flagellum
Eubacterial flagellum is a multifunctional organelle. It is also one of a range of motility systems in bacteria. The structure of the organelle appears like a motor, shaft and a propeller.[8] However, the structure of eubacterial flagellae varies based on whether their motor systems run on protons or sodium, and on the complexity of the flagellar whip.[9] The evolutionary origin of eubacterial flagellae is probably an example of indirect evolution. A hypothesis on the evolutionary pathway of the eubacterial flagellum argues that a secretory system evolved first, based around the SMC rod- and pore-forming complex. This is presumed to be the common ancestor of the type-III secretory system and the flagellar system. Then, an ion pump was introduced to this structure which improved secretion. The ion pump later became the motor protein. This was followed by the emergence of the proto-flagellar filament as part of the protein-secretion structure. Gliding-twitching motility arose at this stage or later and was then refined into swimming motility.[8]
Archaeal flagellum
The recently elucidated archaeal flagellum, or
Sequence comparison indicates that the archaeal flagellum is homologous to bacterial
Further research
Testable outlines exist for the origin of each of the three motility systems, and avenues for further research are clear; for prokaryotes, these avenues include the study of secretion systems in free-living, nonvirulent prokaryotes. In eukaryotes, the mechanisms of both mitosis and cilial construction, including the key role of the centriole, need to be much better understood. A detailed survey of the various nonmotile appendages found in eukaryotes is also necessary.
Finally, the study of the origin of all of these systems would benefit greatly from a resolution of the questions surrounding deep phylogeny, as to what are the most deeply branching organisms in each domain, and what are the interrelationships between the domains.
See also
- Last universal ancestor
References
- PMID 23398214.
- PMID 8681396.
- PMID 11316608.
- PMID 11541392.
- OCLC 39700477.[page needed]
- PMID 33251695.
- ^ Abby S; Rocha E. 2012. The Non-Flagellar Type III Secretion System Evolved from the Bacterial Flagellum and Diversified into Host-Cell Adapted Systems. PLOS Genetics. http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1002983
- ^ ISBN 0-8135-3433-XRutgers University press New Brunswick, New Jersey, and London.72-84.
- ISBN 978-0-12-027749-0. v. 49: 291–337.
- PMID 7908603.
Further reading
- Wong, Tim; Amidi, Arezou; Dodds, Alexandra; Siddiqi, Sara; Wang, Jing; Yep, Tracy; Tamang, Dorjee G.; Saier, Milton H. (2007). "Evolution of the Bacterial Flagellum: Cumulative evidence indicates that flagella developed as modular systems, with many components deriving from other systems" (PDF). Microbe. 2 (7): 335–40. Archived from the original (PDF) on 15 March 2012. Retrieved 1 December 2009.
- Jones, Dan (16 February 2008). "Uncovering the evolution of the bacterial flagellum". New Scientist. Retrieved 1 December 2009.
- Hall JL, Ramanis Z, Luck DJ (October 1989). "Basal body/centriolar DNA: molecular genetic studies in Chlamydomonas". Cell. 59 (1): 121–32. PMID 2571418.
- Pallen MJ, Matzke NJ (October 2006). "From The Origin of Species to the origin of bacterial flagella". Nature Reviews. Microbiology. 4 (10): 784–90. PMID 16953248.
- Margulis, Lynn (1981). Symbiosis in cell evolution: life and its environment on the early Earth. San Francisco: W. H. Freeman. OCLC 6982472.
- Margulis L (April 1993). "The Inheritance of Acquired Microbes" (PDF). Citation Classic Commentaries. 36 (16): 9–10.
External links
- Flagellum Evolution at The Panda's Thumb
- Matzke NJ (September 2006). "Evolution in (Brownian) space: a model for the origin of the bacterial flagellum". Talk Reason. Retrieved 1 December 2009.