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Mixotroph

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Mixotroph

Trophic modes can be expressed on a continuum, with complete auto- and heterotrophy or other combinations of these. Mixotrophs can be either eukaryotic or prokaryotic.[1] They can take advantage of different environmental conditions.[2]

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.[1] Some organisms have incomplete Calvin cycles, so they are incapable of fixing carbon dioxide and must use organic carbon sources.

Contents

  • Types of Mixotrophy 1
  • Examples 2
  • Plants 3
  • See also 4
  • Notes 5
  • External links 6

Types of Mixotrophy

Organisms may employ mixotrophy obligately or facultatively.

  • Obligate mixotrophy: in order 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 sufficent 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.[3]

In order 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 Harriet JL Jones, 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 injestion, 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.

A more recent mixotrophic scheme by Stoeker also takes into account the role of nutrients and growth factors, and includes mixotrophs who have a photosynthetic symbiont or who retain chloroplasts from their prey. This scheme characterizes mixotrophs by their efficiency.

  • Type I: "Ideal Mixotrophs" who utilize prey and sunlight equally well
  • Type 2: Supplement phototrophic activity with food consumation
  • Type 3: Primarily heterotrophic, use phototrophic activity during times of very low prey abundance.[4]

Examples

  • [9][8] conditions; lithoautotrophy takes place aerobically.anaerobic Organoheterotrophy can occur under
    [7][6][5]

Plants

Amongst plants, mixotrophy classically applies to

  • Troost TA, Kooi BW, Kooijman SA (February 2005). "When do mixotrophs specialize? Adaptive dynamics theory applied to a dynamic energy budget model". Math Biosci 193 (2): 159–82.  
  • Sanders, Robert W. Mixotrophic Nutrition of Phytoplankton: Venus Fly Traps of the microbial world. Temple University.

External links

  1. ^ a b Eiler A (December 2006). "Evidence for the Ubiquity of Mixotrophic Bacteria in the Upper Ocean: Implications and Consequences". Appl Environ Microbiol 72 (12): 7431–7.  
  2. ^ Katechakis A, Stibor H (July 2006). "The mixotroph Ochromonas tuberculata may invade and suppress specialist phago- and phototroph plankton communities depending on nutrient conditions". Oecologia 148 (4): 692–701.  
  3. ^ Schoonhoven, Erwin (January 19, 2000). "Ecophysiology of Mixotrophs". Thesis. 
  4. ^ Tarangkoon, Woraporn (29 April 2010). "Mixtrophic Protists among Marine Ciliates and Dinoflagellates: Distribution, Physiology and Ecology". Thesis. 
  5. ^ Libes, Susan M. (2009). Introduction to marine biogeochemistry (2 ed.). Academic Press. p. 192.  
  6. ^ Dworkin, Martin (2006). The Prokaryotes: Ecophysiology and biochemistry 2 (3rd ed.). Springer. p. 988.  
  7. ^ Lengeler, Joseph W.; Drews, Gerhart; Schlegel, Hans Günter (1999). Biology of the Prokaryotes. Georg Thieme Verlag. p. 238.  
  8. ^ Bartosik D, Sochacka M, Baj J (July 2003). "Paracoccus pantotrophus"Identification and Characterization of Transposable Elements of . J Bacteriol 185 (13): 3753–63.  
  9. ^ Friedrich et al., Cornelius G. (2007). "Redox Control of Chemotrophic Sulfur Oxidation of Paracoccus pantotrophus". Microbial Sulfur Metabolism. Springer. pp. 139–150.  PDF
  10. ^ Schmidt, Susanne; John A. Raven; Chanyarat Paungfoo-Lonhienne (2013). "The mixotrophic nature of photosynthetic plants". Functional Plant Biology 40 (5): 425.  

Notes

See also

[10]

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