Osmotrophy is a form of heterotrophic nutrition and a cellular feeding mechanism involving the direct absorption of dissolved organic compounds by osmosis. Organisms that use osmotrophy are called osmotrophs. Osmotrophy is used by diverse groups of organisms. Organisms that use osmotrophy include microorganisms like bacteria, many species of protists and most fungi. Invertebrate animal groups like molluscs, sponges, corals, brachiopods and echinoderms may use osmotrophic feeding as a supplemental food source. A common subset of osmotrophy is lysotrophy, in which organisms secrete enzymes into the extracellular environment to break down macromolecules into smaller, soluble molecules for absorption.
>>>PUT SHARE BUTTONS HERE<<<
👉 Osmotrophy in the context of Extracellular digestion
Extracellular phototropic digestion is a process in which saprobionts feed by secreting enzymes through the cell membrane onto the food. The enzymes catalyze the digestion of the food, i.e., diffusion, transport, osmotrophy or phagocytosis. Since digestion occurs outside the cell, it is said to be extracellular. It takes place either in the lumen of the digestive system, in a gastric cavity or other digestive organ, or completely outside the body. During extracellular digestion, food is broken down outside the cell either mechanically or with acidby special molecules called enzymes. Then the newly broken down nutrients can be absorbed by the cells nearby. Humans use extracellular digestion when they eat. Their teeth grind the food up, enzymes and acid in the stomach liquefy it, and additional enzymes in the small intestine break the food down into parts their cells can use.Extracellular digestion is a form of digestion found in all saprobiontic annelids, crustaceans, arthropods, lichens and chordates, including vertebrates.
In this Dossier
Osmotrophy in the context of Mixotrophic
A mixotroph is an organism that uses a mix of different sources of energy and carbon, instead of having a single trophic mode. Mixotrophs are situated somewhere on the continuum from complete autotrophy to complete heterotrophy. It is estimated that mixotrophs comprise more than half of all microscopic plankton. There are two types of eukaryotic mixotrophs. There are those with their own chloroplasts – including those with endosymbionts providing the chloroplasts. And there are those that acquire them through kleptoplasty, or through symbiotic associations with prey, or through 'enslavement' of the prey's organelles.
Possible combinations include photo- and chemotrophy, besides litho- and organotrophy, the latter including osmotrophy, phagotrophy and myzocytosis. Mixotrophs can be either eukaryotic or prokaryotic. Mixotrophs can take advantage of different environmental conditions.
Osmotrophy in the context of Holomycota
Holomycota or Nucletmycea are a basal Opisthokont clade as sister of the Holozoa. It consists of the Cristidiscoidea and the kingdom Fungi. The position of nucleariids, unicellular free-living phagotrophic amoebae, as the earliest lineage of Holomycota suggests that animals and fungi independently acquired complex multicellularity from a common unicellular ancestor and that the osmotrophic lifestyle (one of the fungal hallmarks) was originated later in the divergence of this eukaryotic lineage. Opisthosporidians is a recently proposed taxonomic group that includes aphelids, Microsporidia and Cryptomycota, three groups of endoparasites.
Rozella (Cryptomycota) is the earliest diverging fungal genus in which chitin has been observed at least in some stages of their life cycle, although the chitinous cell wall (another fungal hallmark) and osmotrophy originated in a common ancestor of Blastocladiomycota and Chytridiomycota, which still contain some ancestral characteristics such as the flagellum in zoosporic stage. The groups of fungi with the characteristic hyphal growth, Zoopagomycota, Mucoromycotina and Dikarya, originated from a common ancestor ~700 Mya. Zoopagomycota are mostly pathogens of animals or other fungi, Mucoromycotina is a more diverse group including parasites, saprotrophs or ectomycorrhizal. Dikarya is the group embracing Ascomycota and Basidiomycota, which comprise ~98% of the described fungal species. Because of this rich diversity, Dikarya includes highly morphologically distinct groups, from hyphae or unicellular yeasts (such as the model organism Saccharomyces cerevisiae) to the complex multicellular fungi popularly known as mushrooms. Contrary to animals and land plants with complex multicellularity, the inferred phylogenetic relationships indicate that fungi acquired and lost multicellularity multiple times along Ascomycota and Basidiomycota evolution.