Paramecium aurelia

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Paramecium aurelia
Paramecium.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Alveolata
Phylum: Ciliophora
Class: Oligohymenophorea
Order: Peniculida
Family: Parameciidae
Genus: Paramecium
Species:
P. aurelia
Binomial name
Paramecium aurelia

Paramecium aurelia [1] are unicellular organisms belonging to the genus Paramecium of the phylum Ciliophora. [2] They are covered in cilia which help in movement and feeding. [2] Paramecium can reproduce sexually, asexually, or by the process of endomixis. [3] Paramecium aurelia demonstrate a strong "sex reaction" whereby groups of individuals will cluster together, and emerge in conjugant pairs. This pairing can last up to 12 hours, during which the micronucleus of each organism will be exchanged. [3] In Paramecium aurelia, a cryptic species complex was discovered by observation. [4] Since then, some have tried to decode this complex using genetic data. [5]

Contents

Physical characteristics

The hair-like cilia that cover the outer body of the paramecium are in constant motion, helping the organism move along at a speed of four times its own length per second. As it moves forward, it rotates on its axis, which aids in pushing food into the gullet. It can move backwards by reversing the motion of the cilia.

Food enters the food vacuoles, which cilia push into the gullet in a process known as phagocytosis, and is digested with the aid of hydrochloric acid and enzymes (Raven and Johnson 1996).[ full citation needed ] When digestion is complete, the remaining food content is emptied into pellicles, known as cytoproct. Osmoregulation is carried out by a pair of contractile vacuoles on either end of the cell, which actively expel water absorbed by osmosis from the surroundings.

Drawing of Paramecium aurelia and its parasites FMIB 50034 Paramecium aurelia and its Parasites.jpeg
Drawing of Paramecium aurelia and its parasites

Taxonomy

Paramecium aurelia is a species complex composed of 15 known species (syngens), which are [5] [6]

Ecology

Scum of algae and cyanobacteria on water surface Cyanobacterial Scum.JPG
Scum of algae and cyanobacteria on water surface

Paramecia are found in freshwater environments, and are especially in scums. Paramecia are attracted by acidic conditions, since they eat bacteria, which often acidify their surroundings. They are an important link in the detrital food web in aquatic ecosystems, eating bacteria and dead organic matter often associated with these bacteria, and being preyed on by protists and small animals.

Aging

Clonal aging, associated with a gradual loss of vitality, occurs in the asexual fission phase of growth of P. tetraurelia, during which cell divisions occur by mitosis rather than meiosis. In P. tetraurelia, the asexual line loses vitality and expires after about 200 fissions if the cells fail to undergo autogamy or conjugation. The basis for this loss of vitality (clonal aging) was clarified by transplantation experiments of Aufderheide in 1986. [7] When macronuclei of clonally young P. tetraurelia were injected into P. tetraurelia of standard clonal age, the lifespan (clonal fissions) of the recipient was prolonged. In contrast, transfer of cytoplasm from clonally young P. tetraurelia did not prolong the lifespan of the recipient. These transplantation experiments indicated that the macronucleus, rather than the cytoplasm, is responsible for clonal aging. Additional experiments by Smith-Sonneborn, [8] Holmes and Holmes, [9] and Gilley and Blackburn [10] showed that, during clonal aging, DNA damage increases dramatically. [11] Thus, DNA damage in the macronucleus appears to be the cause of clonal aging in P. tetraurelia.

Meiosis and rejuvenation

When clonally aged P. tetraurelia are stimulated to undergo meiosis in association with either conjugation or automixis, the genetic descendants are rejuvenated, and are able to have many more mitotic binary fission divisions. During conjugation or automixis, the micronuclei of the cell(s) undergo meiosis, the old macronucleus disintegrates, and a new macronucleus is formed by replication of the micronuclear DNA that had recently undergone meiosis. There is apparently little, if any, DNA damage in the new macronucleus. These findings further support the idea that clonal aging is due, in large part, to a progressive accumulation of DNA damage; and that rejuvenation is due to the repair of this damage in the micronucleus during meiosis. Meiosis appears to be an adaptation for DNA repair and rejuvenation in P. tetraurelia. [12] In P. tetraurelia, CtlP protein is a key factor needed for the completion of meiosis during sexual reproduction and recovery of viable sexual progeny. [12] The CtlP and Mre11 nuclease complex are essential for accurate processing and repair of double-strand breaks during homologous recombination. [12]

The adaptive benefit of meiosis and self-fertilization in response to starvation appears to be independent of the generation of any new genetic variation in P. tetraurelia. [13] This observation suggests that the underlying molecular mechanism of meiosis provides a fitness advantage regardless of any concomitant effect of sex on genetic diversity. [13] [14]

Related Research Articles

<span class="mw-page-title-main">Asexual reproduction</span> Reproduction without a sexual process

Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent and thus the newly created individual is genetically and physically similar to the parent or an exact clone of the parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and bacteria. Many eukaryotic organisms including plants, animals, and fungi can also reproduce asexually. In vertebrates, the most common form of asexual reproduction is parthenogenesis, which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited. Komodo dragons and some monitor lizards can reproduce asexually.

<span class="mw-page-title-main">Reproduction</span> Biological process by which new organisms are generated from one or more parent organisms

Reproduction is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: asexual and sexual.

<i>Tetrahymena</i> Genus of single-celled organisms

Tetrahymena is a genus of free-living ciliates, examples of unicellular eukaryotes. The genus Tetrahymena is the most widely studied member of its phylum. It can produce, store and react with different types of hormones. Tetrahymena cells can recognize both related and hostile cells.

<i>Paramecium</i> Genus of unicellular ciliates, commonly studied as a representative of the ciliate group

Paramecium is a genus of eukaryotic, unicellular ciliates, widespread in freshwater, brackish, and marine environments. Paramecia are often abundant in stagnant basins and ponds. Because some species are readily cultivated and easily induced to conjugate and divide, they have been widely used in classrooms and laboratories to study biological processes. Paramecium species are commonly studied as model organisms of the ciliate group and have been characterized as the "white rats" of the phylum Ciliophora.

<span class="mw-page-title-main">Unicellular organism</span> Organism that consists of only one cell

A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and eukaryotic organisms. Most prokaryotes are unicellular and are classified into bacteria and archaea. Many eukaryotes are multicellular, but some are unicellular such as protozoa, unicellular algae, and unicellular fungi. Unicellular organisms are thought to be the oldest form of life, with early protocells possibly emerging 3.5–4.1 billion years ago.

<span class="mw-page-title-main">Evolution of sexual reproduction</span>

Evolution of sexual reproduction describes how sexually reproducing animals, plants, fungi and protists could have evolved from a common ancestor that was a single-celled eukaryotic species. Sexual reproduction is widespread in eukaryotes, though a few eukaryotic species have secondarily lost the ability to reproduce sexually, such as Bdelloidea, and some plants and animals routinely reproduce asexually without entirely having lost sex. The evolution of sexual reproduction contains two related yet distinct themes: its origin and its maintenance. Bacteria and Archaea (prokaryotes) have processes that can transfer DNA from one cell to another, but it is unclear if these processes are evolutionarily related to sexual reproduction in Eukaryotes. In eukaryotes, true sexual reproduction by meiosis and cell fusion is thought to have arisen in the last eukaryotic common ancestor, possibly via several processes of varying success, and then to have persisted.

Tracy Morton Sonneborn was an American biologist. His life's study was ciliated protozoa of the group Paramecium.

<span class="mw-page-title-main">Nuclear dimorphism</span>

Nuclear dimorphism is a term referred to the special characteristic of having two different kinds of nuclei in a cell. There are many differences between the types of nuclei. This feature is observed in protozoan ciliates, like Tetrahymena, and some foraminifera. Ciliates contain two nucleus types: a macronucleus that is primarily used to control metabolism, and a micronucleus which performs reproductive functions and generates the macronucleus. The compositions of the nuclear pore complexes help determine the properties of the macronucleus and micronucleus. Nuclear dimorphism is subject to complex epigenetic controls. Nuclear dimorphism is continuously being studied to understand exactly how the mechanism works and how it is beneficial to cells. Learning about nuclear dimorphism is beneficial to understanding old eukaryotic mechanisms that have been preserved within these unicellular organisms but did not evolve into multicellular eukaryotes.

Microbial genetics is a subject area within microbiology and genetic engineering. Microbial genetics studies microorganisms for different purposes. The microorganisms that are observed are bacteria and archaea. Some fungi and protozoa are also subjects used to study in this field. The studies of microorganisms involve studies of genotype and expression system. Genotypes are the inherited compositions of an organism. Genetic Engineering is a field of work and study within microbial genetics. The usage of recombinant DNA technology is a process of this work. The process involves creating recombinant DNA molecules through manipulating a DNA sequence. That DNA created is then in contact with a host organism. Cloning is also an example of genetic engineering.

<i>Paramecium caudatum</i> Species of single-celled organism

Paramecium caudatum is a species of unicellular protist in the phylum Ciliophora. They can reach 0.33 mm in length and are covered with minute hair-like organelles called cilia. The cilia are used in locomotion and feeding. The species is very common, and widespread in marine, brackish and freshwater environments.

<span class="mw-page-title-main">Clone (cell biology)</span> Group of identical cells that share a common ancestry

A clone is a group of identical cells that share a common ancestry, meaning they are derived from the same cell.

<span class="mw-page-title-main">Protozoa</span> Single-celled eukaryotic organisms

Protozoa are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically, protozoans were regarded as "one-celled animals".

<span class="mw-page-title-main">Ciliate</span> Taxon of protozoans with hair-like organelles called cilia

The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella. Cilia occur in all members of the group and are variously used in swimming, crawling, attachment, feeding, and sensation.

<span class="mw-page-title-main">Automixis</span> Fusion of nuclei or gametes from same individual

Automixis is the fusion of nuclei or gametes derived from the same individual. The term covers several reproductive mechanisms, some of which are parthenogenetic.

The origin and function of meiosis are currently not well understood scientifically, and would provide fundamental insight into the evolution of sexual reproduction in eukaryotes. There is no current consensus among biologists on the questions of how sex in eukaryotes arose in evolution, what basic function sexual reproduction serves, and why it is maintained, given the basic two-fold cost of sex. It is clear that it evolved over 1.2 billion years ago, and that almost all species which are descendants of the original sexually reproducing species are still sexual reproducers, including plants, fungi, and animals.

<i>Chilodonella uncinata</i> Species of single-celled organism

Chilodonella uncinata is a single-celled organism of the ciliate class of alveoles. As a ciliate, C. uncinata has cilia covering its body and a dual nuclear structure, the micronucleus and macronucleus. Unlike some other ciliates, C. uncinata contains millions of minichromosomes in its macronucleus while its micronucleus is estimated to contain 3 chromosomes. Childonella uncinata is the causative agent of Chilodonelloza, a disease that affects the gills and skin of fresh water fish, and may act as a facultative of mosquito larva.

Paramecium sonneborni is a species of unicellular organisms belonging to the genus Paramecium of the phylum Ciliophora. It was first isolated in Texas and named after Tracy M. Sonneborn. It is a member of the Paramecium aurelia species complex. They are covered in cilia and are distinguished by their difference in mating patterns and enzyme patterns. The length of Paramecium sonneborni is between 130 and 186 μm with a mean length of 154μm. It is the newest member of the Paramecium aurelia species complex. The current Paramecium sonneborni strains, so far, reveal very low viability in the generations and are a result of allopatric speciation.

Autogamy or self-fertilization refers to the fusion of two gametes that come from one individual. Autogamy is predominantly observed in the form of self-pollination, a reproductive mechanism employed by many flowering plants. However, species of protists have also been observed using autogamy as a means of reproduction. Flowering plants engage in autogamy regularly, while the protists that engage in autogamy only do so in stressful environments.

<i>Paramecium biaurelia</i> Species of parasitic protist

Paramecium biaurelia is a species of unicellular ciliates under the genus Paramecium, and one of the cryptic species of Paramecium aurelia. It is a free-living protist in water bodies and harbours several different bacteria as endosymbionts. Although the bacteria are parasites by definition, they also exhibit mutual relationship with the protist by providing survival benefits. It is used as an organism model in the study of the effects of gravitational forces in different environments.

<i>Tetrahymena thermophila</i> Species of ciliate protozoa

Tetrahymena thermophila is a species of Ciliophora in the family Tetrahymenidae. It is a free living protozoon and occurs in fresh water.

References

  1. ↑ "Paramecium aurelia". Integrated Taxonomic Information System.
  2. 1 2 "Paramecium". 101 Science.com. Retrieved 27 September 2016.
  3. 1 2 Sonneborn, T. M. (1937). "Sex, sex inheritance and sex determination in Paramecium Aurelia" (PDF). Proceedings of the National Academy of Sciences of the United States of America. 23 (7): 378–385. Bibcode:1937PNAS...23..378S. doi: 10.1073/pnas.23.7.378 . PMC   1076944 . PMID   16588168 . Retrieved 27 September 2016.
  4. ↑ Sonneborn, T. M. (1975) The Paramecium-aurelia complex of 14 sibling species. Transactions of American Microscope Society, 94: 155–178.
  5. 1 2 Catania F, Wurmser F, Potekhin AA, Przybos E, Lynch M (2009). "Genetic Diversity in the Paramecium aurelia Species Complex". Molecular Biology and Evolution. 26 (2): 421–431. doi:10.1093/molbev/msn266. PMC   3888249 . PMID   19023087.
  6. ↑ Aufderheide, Karl J.; Daggett, Pierre-Marc; Nerad, Thomas A. (1983). "Paramecium sonneborni n. sp., a New Member of the Paramecium aurelia Species-Complex". The Journal of Eukaryotic Microbiology. 30 (1): 128–131. doi:10.1111/j.1550-7408.1983.tb01046.x. ISSN   1066-5234.
  7. ↑ Aufderheide, Karl J. (1986). "Clonal aging in Paramecium tetraurelia. II. Evidence of functional changes in the macronucleus with age". Mechanisms of Ageing and Development. 37 (3): 265–279. doi:10.1016/0047-6374(86)90044-8. PMID   3553762. S2CID   28320562.
  8. ↑ Smith-Sonneborn, J. (1979). "DNA repair and longevity assurance in Paramecium tetraurelia". Science . 203 (4385): 1115–1117. Bibcode:1979Sci...203.1115S. doi:10.1126/science.424739. PMID   424739.
  9. ↑ Holmes, George E.; Holmes, Norreen R. (July 1986). "Accumulation of DNA damages in aging Paramecium tetraurelia". Molecular and General Genetics. 204 (1): 108–114. doi:10.1007/bf00330196. PMID   3091993. S2CID   11992591.
  10. ↑ Gilley, David; Blackburn, Elizabeth H. (1994). "Lack of telomere shortening during senescence in Paramecium" (PDF). Proceedings of the National Academy of Sciences of the United States of America . 91 (5): 1955–1958. Bibcode:1994PNAS...91.1955G. doi: 10.1073/pnas.91.5.1955 . PMC   43283 . PMID   8127914.
  11. ↑ Bernstein, H; Bernstein, C (1991). Aging, Sex, and DNA Repair. San Diego: Academic Press. pp. 153–156. ISBN   978-0120928606.
  12. 1 2 3 Godau, Julia; Ferretti, Lorenza P.; Trenner, Anika; Dubois, Emeline; von Aesch, Christine; Marmignon, Antoine; Simon, Lauriane; Kapusta, Aurélie; Guérois, Raphaël; Bétermier, Mireille; Sartori, Alessandro A. (2019). "Identification of a miniature Sae2/Ctp1/CtIP ortholog from Paramecium tetraurelia required for sexual reproduction and DNA double-strand break repair" (PDF). DNA Repair. 77: 96–108. doi:10.1016/j.dnarep.2019.03.011. PMID   30928893. S2CID   89619084.
  13. 1 2 Thind AS, Vitali V, Guarracino MR, Catania F (May 2020). "What's Genetic Variation Got to Do with It? Starvation-Induced Self-Fertilization Enhances Survival in Paramecium". Genome Biol Evol. 12 (5): 626–638. doi:10.1093/gbe/evaa052. PMC   7239694 . PMID   32163147.
  14. ↑ Bernstein H, Byerly HC, Hopf FA, Michod RE (September 1985). "Genetic damage, mutation, and the evolution of sex". Science. 229 (4719): 1277–81. doi:10.1126/science.3898363. PMID   3898363.
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