Mixotroph

Source: Wikipedia, the free encyclopedia.
(Redirected from
Mixotrophy
)

A mixotroph is an organism that can use a mix of different

heterotrophy at the other. It is estimated that mixotrophs comprise more than half of all microscopic plankton.[1] There are two types of eukaryotic mixotrophs: those with their own chloroplasts, and those with endosymbionts—and those that acquire them through kleptoplasty or through symbiotic associations with prey or enslavement of their organelles.[2]

Possible combinations are photo- and chemotrophy, litho- and organotrophy (osmotrophy, phagotrophy and myzocytosis), auto- and heterotrophy or other combinations of these. Mixotrophs can be either eukaryotic or prokaryotic.[3] They can take advantage of different environmental conditions.[4]

If a trophic mode is obligate, then it is always necessary for sustaining growth and maintenance; if facultative, it can be used as a supplemental source.

organic carbon
sources.

Overview

Organisms may employ mixotrophy obligately or facultatively.

  • Obligate mixotrophy: To support growth and maintenance, an organism must utilize both heterotrophic and autotrophic means.
  • Obligate autotrophy with facultative heterotrophy: Autotrophy alone is sufficient for growth and maintenance, but heterotrophy may be used as a supplementary strategy when autotrophic energy is not enough, for example, when light intensity is low.
  • Facultative autotrophy with obligate heterotrophy: Heterotrophy is sufficient for growth and maintenance, but autotrophy may be used to supplement, for example, when prey availability is very low.
  • Facultative mixotrophy: Maintenance and growth may be obtained by heterotrophic or autotrophic means alone, and mixotrophy is used only when necessary.[5]

Plants

A mixotrophic plant using mycorrhizal fungi to obtain photosynthesis products from other plants

Amongst plants, mixotrophy classically applies to carnivorous, hemi-parasitic and myco-heterotrophic species. However, this characterisation as mixotrophic could be extended to a higher number of clades as research demonstrates that organic forms of nitrogen and phosphorus — such as DNA, proteins, amino-acids or carbohydrates — are also part of the nutrient supplies of a number of plant species.[6]

Animals

Mixotrophy is less common among animals than among plants and microbes, but there are many examples of mixotrophic invertebrates and at least one example of a mixotrophic vertebrate.

  • The spotted salamander,
    symbiotic algae living inside them,[7] the only known example of vertebrate cells hosting an endosymbiont microbe (unless mitochondria is considered).[8][9]
  • Reef-building corals (Scleractinia), like many other cnidarians (e.g. jellyfish, anemones), host endosymbiotic microalgae within their cells, thus making them mixotrophs.
  • The Oriental hornet, Vespa orientalis, can obtain energy from sunlight absorbed by its cuticle.[11] It thus contrasts with the other animals listed here, which are mixotrophic with the help of endosymbionts.

Microorganisms

See also:
Marine mixotrophs and Mixotrophic dinoflagellate

Bacteria and archaea

  • electron donors and are consumed to produce ATP. The carbon source for these organisms can be carbon dioxide (autotrophy) or organic carbon (heterotrophy).[13][14][15]
    Organoheterotrophy can occur under aerobic or under anaerobic conditions; lithoautotrophy takes place aerobically.[16][17]

Protists

Traditional classification of mixotrophic protists
In this diagram, types in open boxes as proposed by Stoecker [18] have been aligned against groups in grey boxes as proposed by Jones.[19][20]
                              DIN = dissolved inorganic nutrients

To characterize the sub-domains within mixotrophy, several very similar categorization schemes have been suggested. Consider the example of a marine protist with heterotrophic and photosynthetic capabilities: In the breakdown put forward by Jones,[19] there are four mixotrophic groups based on relative roles of phagotrophy and phototrophy.

  • A: Heterotrophy (phagotrophy) is the norm, and phototrophy is only used when prey concentrations are limiting.
  • B: Phototrophy is the dominant strategy, and phagotrophy is employed as a supplement when light is limiting.
  • C: Phototrophy results in substances for both growth and ingestion, phagotrophy is employed when light is limiting.
  • D: Phototrophy is most common nutrition type, phagotrophy only used during prolonged dark periods, when light is extremely limiting.

An alternative scheme by Stoeker[18] also takes into account the role of nutrients and growth factors, and includes mixotrophs that have a photosynthetic symbiont or who retain chloroplasts from their prey. This scheme characterizes mixotrophs by their efficiency.

  • Type 1: "Ideal mixotrophs" that use prey and sunlight equally well
  • Type 2: Supplement phototrophic activity with food consumption
  • Type 3: Primarily heterotrophic, use phototrophic activity during times of very low prey abundance.[21]

Another scheme, proposed by Mitra et al., specifically classifies marine planktonic mixotrophs so that mixotrophy can be included in ecosystem modeling.[20] This scheme classified organisms as:

  • Constitutive mixtotrophs (CMs): phagotrophic organisms that are inherently able to also photosynthesize
  • Non-constitutive mixotrophs (NCMs): phagotrophic organisms that must ingest prey to attain the ability to photosynthesize. NCMs are further broken down into:
    • Specific non-constitutive mixotrophs (SNCMs), which only gain the ability to photosynthesize from a specific prey item (either by retaining plastids only in kleptoplastidy or by retaining whole prey cells in endosymbiosis)
    • General non-constitutive mixotrophs (GNCM), which can gain the ability to photosynthesize from a variety of prey items


Pathways used by Mitra et al. to derive functional groups of planktonic protists [20]
Levels in complexity among those different types of protists, according to Mitra et al. [20]
(A) phagotrophic (no phototrophy); (B) phototrophic (no phagotrophy); (C) constitutive mixotroph, with innate capacity for phototrophy; (D) generalist non-constitutive mixotroph acquiring photosystems from different phototrophic prey; (E) specialist non-constitutive mixotroph acquiring plastids from a specific prey type; (F) specialist non-constitutive mixotroph acquiring photosystems from endosymbionts. DIM = dissolved inorganic material (ammonium, phosphate etc.).                               DOM =
dissolved organic material

See also

Notes

  1. ^ Beware the mixotrophs - they can destroy entire ecosystems 'in a matter of hours'
  2. ^ [S. G. Leles et al, Oceanic protists with different forms of acquired phototrophy display contrasting biogeographies and abundance, Proceedings of the Royal Society B: Biological Sciences (2017).]
  3. ^
    PMID 17028233
    .
  4. S2CID 22837754
    .
  5. ^ Schoonhoven, Erwin (January 19, 2000). "Ecophysiology of Mixotrophs" (PDF). Thesis.
  6. PMID 32481119
    .
  7. ISSN 0028-0836
    .
  8. ^ Frazer, Jennifer (May 18, 2018). "Algae Living inside Salamanders Aren't Happy about the Situation". Scientific American Blog Network.
  9. PMID 28462779
    .
  10. JSTOR 1224630
    .
  11. S2CID 14022197.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  12. S2CID 208553146
    .
  13. ISBN 978-0-7637-5345-0
    .
  14. ISBN 978-0-387-25492-0
    .
  15. ISBN 978-3-13-108411-8
    .
  16. PMID 12813068
    .
  17. ^ Friedrich, Cornelius G.; et al. (2007). "Redox Control of Chemotrophic Sulfur Oxidation of Paracoccus pantotrophus". Microbial Sulfur Metabolism. Springer. pp. 139–150.[permanent dead link] PDF[dead link]
  18. ^
    doi:10.1016/S0932-4739(98)80055-2
    .
  19. ^
    doi:10.1046/j.1365-2427.1997.00138.x
    .
  20. ^
    PMID 26927496. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License
    .
  21. ^ Tarangkoon, Woraporn (29 April 2010). "Mixtrophic Protists among Marine Ciliates and Dinoflagellates: Distribution, Physiology and Ecology" (PDF). Thesis.[permanent dead link]

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Mixotroph&oldid=1193756164"