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. They can take advantage of different environmental conditions.
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. Some organisms have incomplete Calvin cycles, so they are incapable of fixing carbon dioxide and must use organic carbon sources.
- 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.
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.
 conditions; lithoautotrophy takes place aerobically.anaerobic
Organoheterotrophy can occur under
- Many examples of the genus Euglena.
- Oriental hornet Vespa orientalis
- Venus Flytrap Dionaea muscipula
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.
- 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.
- 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.
- Schoonhoven, Erwin (January 19, 2000). "Ecophysiology of Mixotrophs". Thesis.
- Tarangkoon, Woraporn (29 April 2010). "Mixtrophic Protists among Marine Ciliates and Dinoflagellates: Distribution, Physiology and Ecology". Thesis.
- Libes, Susan M. (2009). Introduction to marine biogeochemistry (2 ed.). Academic Press. p. 192.
- Dworkin, Martin (2006). The Prokaryotes: Ecophysiology and biochemistry 2 (3rd ed.). Springer. p. 988.
- Lengeler, Joseph W.; Drews, Gerhart; Schlegel, Hans Günter (1999). Biology of the Prokaryotes. Georg Thieme Verlag. p. 238.
- Bartosik D, Sochacka M, Baj J (July 2003). "Paracoccus pantotrophus"Identification and Characterization of Transposable Elements of . J Bacteriol 185 (13): 3753–63.
- Friedrich et al., Cornelius G. (2007). "Redox Control of Chemotrophic Sulfur Oxidation of Paracoccus pantotrophus". Microbial Sulfur Metabolism. Springer. pp. 139–150. PDF
- Schmidt, Susanne; John A. Raven; Chanyarat Paungfoo-Lonhienne (2013). "The mixotrophic nature of photosynthetic plants". Functional Plant Biology 40 (5): 425.