Radiosynthesis (metabolism)

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Radiosynthesis is the theorized capture and metabolism, by living organisms, of energy from ionizing radiation, analogously to photosynthesis. Metabolism of ionizing radiation was theorized as early as 1956 by the Russian S. I. Kuznetsov. [1]

Beginning in the 1990s, researchers at the Chernobyl Nuclear Power Plant uncovered some 200 species of apparently radiotrophic fungi containing the pigment melanin on the walls of the reactor room and in the surrounding soil. [2] [3] Such "melanized" fungi have also been discovered in nutrient-poor, high-altitude areas which are exposed to high levels of ultraviolet radiation. [4]

Following the Russian results, an American team at the Albert Einstein College of Medicine of Yeshiva University in New York began experimenting with radiation exposure of melanin and melanized fungi. They found that ionizing radiation increased the ability of melanin to support an important metabolic reaction, and that Cryptococcus neoformans fungi grew three times faster than normal. [5] [4] Microbiologist Ekaterina Dadachova suggested such fungi could serve as a food supply and source of radiation protection for interplanetary astronauts, who would be exposed to cosmic rays. [4]

In 2014, the American research group was awarded a patent for a method of enhancing the growth of microorganisms through increasing melanin content. The inventors of this process claimed their fungi were employing radiosynthesis, and hypothesized that radiosynthesis may have played a role in early life on Earth, by allowing melanized fungi to act as autotrophs. [6]

From October 2018 through March 2019, NASA conducted an experiment aboard the International Space Station to study radiotrophic fungi as a potential radiation barrier to the harmful radiation in space. Radiotrophic fungi have many possible applications on Earth as well, potentially including a disposal method for nuclear waste or use as high-altitude biofuel or a nutrition source. [7]

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Radiation Waves or particles propagating through space or through a medium, carrying energy

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Melanin Group of natural pigments found in most organisms

Melanin is a broad term for a group of natural pigments found in most organisms. Melanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino acid tyrosine is followed by polymerization. The melanin pigments are produced in a specialized group of cells known as melanocytes.

<i>Cryptococcus</i> Genus of fungi

Cryptococcus, sometimes informally called crypto, is a genus of fungi that grow in culture as yeasts. The sexual forms or teleomorphs of Cryptococcus species are filamentous fungi formerly classified in the genus Filobasidiella. The name Cryptococcus is used when referring to the yeast states of the fungi; it comes from the Greek for "hidden sphere". A few species in the Cryptococcus genus cause a disease called cryptococcosis.

<i>Cryptococcus neoformans</i> Species of yeast

Cryptococcus neoformans is an encapsulated yeast and an obligate aerobe that can live in both plants and animals. Its teleomorph is Filobasidiella neoformans, a filamentous fungus belonging to the class Tremellomycetes. It is often found in bird excrement. Cryptococcus neoformans is an encapsulated fungal organism and it can cause disease in apparently immunocompetent, as well as immunocompromised, hosts.

Radioresistance is the level of ionizing radiation that organisms are able to withstand.

Effects of the Chernobyl disaster Overview of the effects of the Chernoby disaster

The 1986 Chernobyl disaster triggered the release of substantial amounts of radioactive contamination into the atmosphere in the form of both particulate and gaseous radioisotopes. As of 2021, it is the most significant unintentional release of radioactivity into the environment.

Mycelial cord

Mycelial cords are linear aggregations of parallel-oriented hyphae. The mature cords are composed of wide, empty vessel hyphae surrounded by narrower sheathing hyphae. Cords may look similar to plant roots, and also frequently have similar functions; hence they are also called rhizomorphs. As well as growing underground or on the surface of trees and other plants, some fungi make mycelial cords which hang in the air from vegetation.

<i>Setosphaeria rostrata</i> Species of fungus

Setosphaeria rostrata is a heat tolerant fungus with an asexual reproductive form (anamorph) known as Exserohilum rostratum. This fungus is a common plant pathogen, causing leaf spots as well as crown rot and root rot in grasses. It is also found in soils and on textiles in subtropical and tropical regions. Exserohilum rostratum is one of the 35 Exserohilum species implicated uncommonly as opportunistic pathogens of humans where it is an etiologic agent of sinusitis, keratitis, skin lesions and an often fatal meningoencephalitis. Infections caused by this species are most often seen in regions with hot climates like Israel, India and the southern USA.

Radiotrophic fungus Fungus that use radiation as an energy source

Radiotrophic fungi are fungi that can use radiation as an energy source to stimulate growth. Radiotrophic fungi have been found in extreme environments such as in the Chernobyl Nuclear Power Plant.

Radioecology

Radioecology is the branch of ecology concerning the presence of radioactivity in Earth’s ecosystems. Investigations in radioecology include field sampling, experimental field and laboratory procedures, and the development of environmentally predictive simulation models in an attempt to understand the migration methods of radioactive material throughout the environment.

EXPOSE External facility on the ISS dedicated to astrobiology experiments

EXPOSE is a multi-user facility mounted outside the International Space Station (ISS) dedicated to astrobiology. EXPOSE was developed by the European Space Agency (ESA) for long-term spaceflights and was designed to allow exposure of chemical and biological samples to outer space while recording data during exposure.

Fungus Biological kingdom, separate from plants and animals

A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from the other eukaryotic kingdoms, which by one traditional classification include Plantae, Animalia, Protozoa, and Chromista.

<i>Deinococcus radiodurans</i> Species of bacterium

Deinococcus radiodurans is an extremophilic bacterium and one of the most radiation-resistant organisms known. It can survive cold, dehydration, vacuum, and acid, and therefore is known as a polyextremophile. It has been listed as the world's toughest known bacterium in The Guinness Book Of World Records.

Autotroph Organism type

An autotroph or primary producer is an organism that produces complex organic compounds using carbon from simple substances such as carbon dioxide, generally using energy from light (photosynthesis) or inorganic chemical reactions (chemosynthesis). They convert an abiotic source of energy into energy stored in organic compounds, which can be used by other organisms. Autotrophs do not need a living source of carbon or energy and are the producers in a food chain, such as plants on land or algae in water. Autotrophs can reduce carbon dioxide to make organic compounds for biosynthesis and as stored chemical fuel. Most autotrophs use water as the reducing agent, but some can use other hydrogen compounds such as hydrogen sulfide.

“Black yeasts”, sometimes also black fungi, dematiaceous fungi, microcolonial fungi or meristematic fungi is a diverse group of slow-growing microfungi which reproduce mostly asexually. Only few genera reproduce by budding cells, while in others hyphal or meristematic (isodiametric) reproduction is preponderant. Black yeasts share some distinctive characteristics, in particular melanisation of their cell wall. Morphological plasticity, incrustation of the cell wall with melanins and presence of other protective substances like carotenoids and mycosporines represent passive physiological adaptations which enable black fungi to be highly resistant against environmental stresses. The term "polyextremotolerance" has been introduced to describe this phenotype, a good example of which is the species Aureobasidium pullulans. Presence of 1,8-dihydroxynaphthalene melanin in the cell wall confers to the microfungi their characteristic olivaceous to dark brown/black colour.

Arturo Casadevall is a Bloomberg Distinguished Professor of Molecular Microbiology & Immunology and Infectious Diseases at the Johns Hopkins Bloomberg School of Public Health and Johns Hopkins School of Medicine, and the Alfred and Jill Sommer Professor and Chair of the W. Harry Feinstone Department of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health. He is an internationally recognized expert in infectious disease research, with a focus on fungal and bacterial pathogenesis and basic immunology of antibody structure-function.

<i>Azotobacter chroococcum</i> Species of bacterium

Azotobacter chroococcum is a bacterium that has the ability to fix atmospheric nitrogen. It was discovered by Martinus Beijerinck in 1901, and was the first aerobic, free-living nitrogen fixer discovered. A. chroococcum could be useful for nitrogen fixation in crops as a biofertilizer, fungicide, and nutrient indicator, and in bioremediation.

Cryomyces antarcticus is a fungus of uncertain placement in the class Dothideomycetes, division Ascomycota. Found in Antarctica, it was described as new to science in 2005. It has been found to be able to survive the harsh outer space environment and cosmic radiation. A proposed mechanistic contributor to the unique resilience observed in C. antarcticus is the presence of its thick and highly melanized cell walls. This melanin may act to protect DNA from damage while C. antarcticus is exposed to conditions that are unsuitable for typical DNA repair systems to function.

Bioremediation of radioactive waste

Bioremediation of radioactive waste or bioremediation of radionuclides is an application of bioremediation based on the use of biological agents bacteria, plants and fungi to catalyze chemical reactions that allow the decontamination of sites affected by radionuclides. These radioactive particles are by-products generated as a result of activities related to nuclear energy and constitute a pollution and a radiotoxicity problem due to its unstable nature of ionizing radiation emissions.

<i>Cladosporium sphaerospermum</i> Species of fungus

Cladosporium sphaerospermum is a radiotrophic fungus belonging to the genus Cladosporium and was described in 1886 by Albert Julius Otto Penzig from the decaying leaves and branches of Citrus. It is a dematiaceous (darkly-pigmented) fungus characterized by slow growth and largely asexual reproduction. Cladosporium sphaerospermum consists of a complex of poorly morphologically differentiated, "cryptic" species that share many physiological and ecological attributes. In older literature, all of these sibling species were classified as C. sphaerospermum despite their unique nature. Accordingly, there is confusion in older literature reports on the physiological and habitat regularities of C. sphaerospermum in the strict sense. This fungus is most phylogenetically similar to C. fusiforme. According to modern phylogenetic analyses, the previously synonymized species, Cladosporium langeroni, is a distinct species.

References

  1. ↑ Kuznetsov, S. I. (March 1, 1956). "On the Question of Possibility of "Radiosynthesis"". Mikrobiologiya (in Russian). 25. OSTI   4367507.
  2. ↑ Zhdanova, N. N.; Vasilevskaya, A.I.; Artyshkova, L. V.; Sadovnikov, Y. S.; Lashko, T. N.; Gavrilyuk, V. I.; Dighton, J. (July 1994). "Changes in micromycete communities in soil in response to pollution by long-lived radionuclides emitted in the Chernobyl accident". Mycological Research. 98 (7): 789–795. doi:10.1016/S0953-7562(09)81057-5.
  3. ↑ Zhdanova, Nelli N.; Tugay, Tatyana; Dighton, John; Zheltonozhsky, Victor; Mcdermott, Patrick (September 2004). "Ionizing radiation attracts soil fungi". Mycological Research. 108 (9): 1089–1096. doi:10.1017/S0953756204000966. PMID   15506020.
  4. 1 2 3 Balter, Michael (May 23, 2007). "Zapped By Radiation, Fungi Flourish". Science. Retrieved 2 November 2017.
  5. ↑ Dadachova, Ekaterina; Bryan, Ruth A.; Huang, Xianchun; Moadel, Tiffany; Schweitzer, Andrew D.; Aisen, Philip; Nosanchuk, Joshua D.; Casadevall, Arturo (May 23, 2007). "Ionizing Radiation Changes the Electronic Properties of Melanin and Enhances the Growth of Melanized Fungi". PLOS ONE. 2 (5): e457. Bibcode:2007PLoSO...2..457D. doi: 10.1371/journal.pone.0000457 . PMC   1866175 . PMID   17520016.
  6. ↑ B2 USpatent 8652827 B2,Dadachova, Ekaterina; Bryan, Ruth; Casadevall, Arturo,"Radiosynthesis as an alternative energy utilization process in melanized organisms and uses thereof",published February 18, 2014, assigned to Albert Einstein College of Medicine of Yeshiva University
  7. ↑ "Experiment Details".
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