Saprotrophy
In ecology, saprotrophy is the name given to the dependence that many organisms, called saprotrophs, have for their nutrition on residues from other organisms, such as dead leaves, corpses or excrement, with an extracellular and external digestion. The phenomenon can also be called saprobiosis and the organisms that represent it, saprobes (generally used as an adjective) or saprobionts. They contribute to the decomposition of organic matter and maintain soil fertility.
Among the saprotrophs we can distinguish the obligate saprotrophs, that is, those that have no other way of obtaining nutrients, and the facultative saprotrophs, those that during most of of their lives they use another means of nutrition and are only saprotrophs during one phase, like the normally parasitic Venturia pyrina.
A saprophyte (from the Greek σαπρος, saprós, "rotten" and φυτος phytos, "plant& #34;) is a heterotrophic organism that obtains its energy from dead organic matter or from the debris discarded by other living beings, from which it extracts the organic compounds it requires as nutrients. The term is only applicable to osmotrophic organisms, traditionally treated as vegetables, although they are rarely plants in the strict sense, being more often protists, and above all bacteria or fungi. some saprobe fungi have the ability to modify the pH of the medium, these fungi are generally green fungi belonging to the genus Penicillium, there are also black or dematiaceous fungi. Bacteria of the genus Pseudomonas also have the ability to grow in the presence of gentamicide and can change the color of the medium to yellow or red. The use of this term is still current, despite the loss of content that the concept of vegetable has suffered with the progress of classification. vegetal kingdom. The use of the word decomposer in ecology approximates this meaning, although it is also sometimes used in the broader sense of saprotroph.
Saprophytes are almost invariably cell-walled organisms that perform osmotrophic nutrition. They first secrete enzymes that hydrolyze the organic molecules in the waste, thus releasing soluble biomolecules that are then absorbed by osmosis through their cell envelopes, cell wall, and plasma membrane. Theirs is a crucial activity in the trophic chain, since it is the first step in a process, decomposition, which returns to the environment in the form of free ions the components used by dead organisms, closing the nutrient cycles. Decomposers act on all kinds of organic remains and in some cases, only they are capable of profitably reusing some compounds.
For a long time, some plants—some orchids and all species in the Monotropaceae family—that lack chlorophyll and are therefore unable to photosynthesize the energy they require were also considered saprotrophs. However, recent research indicates that these plants actually parasitize other plants, often using a fungus with which their roots are in a symbiotic relationship (a mycorrhizal relationship); contemporary literature calls them myco-heterotrophs. Examples of this class of plants include Monotropa uniflora and Neottia nidus-avis.
Saprophages are phagotrophic feeding organisms that actively ingest solid material, instead of dissolved substances, which they then digest within the framework of the organism, in phagosomes for unicellular animals, in the digestive tract for multicellular animals. The small phagotrophs that process residues, especially vegetables, and that are very important in the edaphon, that is, the biota of the soil, are called "detritivores". The term is also used, less commonly, to refer to animals that feed on carrion, such as vultures or hyenas.