Astrovirology

Last updated

Astrovirology is an emerging subdiscipline of astrobiology which aims to understand what role viruses played in the origin and evolution of life on Earth as well as the potential for viruses beyond Earth.

Contents

Viruses and early life on Earth

Viruses drive evolution

Viruses are a major driving force in evolution; the arms race between viruses and their host, or the Red Queen hypothesis, causes strong evolutionary pressures in both the host and viruses. [1] The host evolves to evade and destroy viruses, while the virus evolves mechanisms to continue infecting the host. Evolution is also influenced by viral horizontal gene transfer. Viral genes can be inserted into the host genome (ex. Retroviruses) and sometimes these genes are evolutionarily favorable. One common example of beneficial horizontal gene transfer in humans is the gene for syncytin, which came from ancient viruses and is important in placenta development.

Viruses influence major evolutionary events

Though unproven, some virologists posit that viruses may have played an important role in major evolutionary events, including the emergence of a DNA genome from an RNA world, divergence from LUCA to the three domains of life, archaea, bacteria, and eukarya, and development of multicellularity. [1] Emergence of a DNA genome and divergence from LUCA may have been aided by horizontal gene transfer of polymerases and other gene-editing enzymes from viruses. Meanwhile, viral selection pressures could have also aided divergence from LUCA to defend against different viruses, while multicellularity provides greater cell population protection from viruses. [1]

Viruses and Earth's environment

Viruses influence biogeochemical cycles

Viruses cause nutrient cycling in the ocean via the viral shunt, and up to 25% of the available carbon in the upper ocean is attributed to virus-induced cell lysis. [1]

Around 5% of Earth's oxygen is thought to be produced by cells infected by viruses encoding photosynthetic genes otherwise absent from the cell. [1] For example, some viruses of cyanobacteria contain genes for Photosystem II, which allows those cyanobacteria to photosynthesize and live in a different part of the ocean as their non-infected counterparts. Some viruses encode other metabolic genes that allow new metabolic functions in their host, for example, phosphate, carbon, and sulfur metabolism.

Extremophile viruses

Viruses have been found in extremely hot, cold, and acidic natural environments, up to 93 °C (199 °F), down to −12 °C (10 °F), and down to pH 1.5. [2]

Viruses in space

Infectivity in space

Viruses including tobacco mosaic virus, poliovirus, and bacteriophage T1 have maintained infectivity after being exposed to space-like conditions including interstellar radiation, low temperature, and low pressure. [1] Further studies are needed to assess the risk of viral hitchhikers, but any virus infecting an organism inside a habitable spacecraft can survive as long as that organism survives.

Effect on astronauts

Latent viruses such as herpes virus, prevalent in humans, can become reactive during spaceflight due to spaceflight stressors. While astronauts experienced few if any symptoms, the potential for other viruses to become reactivated or more virulent is a substantial threat. [3]

Furthermore, some bacteria ( Serratia marcescens ) have been found to be more virulent in spaceflight conditions, leading to a question of whether viruses could also become more virulent. [4]

Forward contamination potential

Limiting forward contamination is critical to be confident in the results of life detection efforts. Bacteria pose a significant contamination challenge in spacecraft assembly clean rooms despite decontamination procedures. [5] However, viruses were found to be present at relatively low levels, based on a metagenomic analysis. [6] Another metagenomic study detected viable human viruses, including herpesvirus and cycloviruses. [7]

Back contamination potential

Life (and viruses) on other planetary bodies have two important potential origins: from Earth or from a second genesis (life originated on that planet). Ancient viruses could have been transported from Earth to another planetary body, perhaps following a massive meteorite impact or volcanic eruption. [1] If this occurred, these viruses would likely be very biological similar to modern organisms. [2] There may be minimal or no immunity among Earth life against the ancient virus, and whatever organism it can infect may be crippled by its re-introduction.

If extraterrestrial viruses are part of a second genesis, their infectivity of Earth life depends on how they encode their genetic information. While their encoding could be incompatible with Earth life, it is also possible that RNA, DNA, or similar molecules could encode for life in the second genesis. In this case, Earth life may be a suitable host. [2]

Potential biosignatures/detection methods

While viruses may or may not be "alive", detection of virions on another planet would be powerful indirect evidence for life. [1] The following methods could offer biosignatures with varying levels of usefulness:

Proposed and current life detection missions

Astrovirologists have called for proposed missions to sample the water plumes of Enceladus and/or Europa for viruses. [1] Others have called for virus detection as part of Mars rover missions like the Rosalind Franklin rover. [9] However, given the lack of validated biosignatures to detect viruses in situ, sample return to Earth has been recommended, [9] which would allow use of TEM and other detection methods requiring complex sample preparation and/or large equipment. The Mars 2020 Perseverance rover has equipment to drill regolith samples and store them for sample return on a future Mars mission. [10]

Related Research Articles

<span class="mw-page-title-main">Bacteriophage</span> Virus that infects and replicates within bacteria

A bacteriophage, also known informally as a phage, is a virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν, meaning "to devour". Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome, and may have structures that are either simple or elaborate. Their genomes may encode as few as four genes and as many as hundreds of genes. Phages replicate within the bacterium following the injection of their genome into its cytoplasm.

Viral evolution is a subfield of evolutionary biology and virology that is specifically concerned with the evolution of viruses. Viruses have short generation times, and many—in particular RNA viruses—have relatively high mutation rates. Although most viral mutations confer no benefit and often even prove deleterious to viruses, the rapid rate of viral mutation combined with natural selection allows viruses to quickly adapt to changes in their host environment. In addition, because viruses typically produce many copies in an infected host, mutated genes can be passed on to many offspring quickly. Although the chance of mutations and evolution can change depending on the type of virus, viruses overall have high chances for mutations.

<span class="mw-page-title-main">Lytic cycle</span> Cycle of viral reproduction

The lytic cycle is one of the two cycles of viral reproduction, the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane. Bacteriophages that only use the lytic cycle are called virulent phages.

<span class="mw-page-title-main">Viral vector</span> Biotechnology to deliver genetic material into a cell

Viral vectors are tools commonly used by molecular biologists to deliver genetic material into cells. This process can be performed inside a living organism or in cell culture. Viruses have evolved specialized molecular mechanisms to efficiently transport their genomes inside the cells they infect. Delivery of genes or other genetic material by a vector is termed transduction and the infected cells are described as transduced. Molecular biologists first harnessed this machinery in the 1970s. Paul Berg used a modified SV40 virus containing DNA from the bacteriophage λ to infect monkey kidney cells maintained in culture.

<i>Molluscum contagiosum virus</i> Species of virus

Molluscum contagiosum virus (MCV) is a species of DNA poxvirus that causes the human skin infection molluscum contagiosum. Molluscum contagiosum affects about 200,000 people a year, about 1% of all diagnosed skin diseases. Diagnosis is based on the size and shape of the skin lesions and can be confirmed with a biopsy, as the virus cannot be routinely cultured. Molluscum contagiosum virus is the only species in the genus Molluscipoxvirus. MCV is a member of the subfamily Chordopoxvirinae of family Poxviridae. Other commonly known viruses that reside in the subfamily Chordopoxvirinae are variola virus and monkeypox virus.

<span class="mw-page-title-main">Cyanophage</span> Virus that infects cyanobacteria

Cyanophages are viruses that infect cyanobacteria, also known as Cyanophyta or blue-green algae. Cyanobacteria are a phylum of bacteria that obtain their energy through the process of photosynthesis. Although cyanobacteria metabolize photoautotrophically like eukaryotic plants, they have prokaryotic cell structure. Cyanophages can be found in both freshwater and marine environments. Marine and freshwater cyanophages have icosahedral heads, which contain double-stranded DNA, attached to a tail by connector proteins. The size of the head and tail vary among species of cyanophages. Cyanophages infect a wide range of cyanobacteria and are key regulators of the cyanobacterial populations in aquatic environments, and may aid in the prevention of cyanobacterial blooms in freshwater and marine ecosystems. These blooms can pose a danger to humans and other animals, particularly in eutrophic freshwater lakes. Infection by these viruses is highly prevalent in cells belonging to Synechococcus spp. in marine environments, where up to 5% of cells belonging to marine cyanobacterial cells have been reported to contain mature phage particles.

Phycodnaviridae is a family of large (100–560 kb) double-stranded DNA viruses that infect marine or freshwater eukaryotic algae. Viruses within this family have a similar morphology, with an icosahedral capsid. As of 2014, there were 33 species in this family, divided among 6 genera. This family belongs to a super-group of large viruses known as nucleocytoplasmic large DNA viruses. Evidence was published in 2014 suggesting that specific strains of Phycodnaviridae might infect humans rather than just algal species, as was previously believed. Most genera under this family enter the host cell by cell receptor endocytosis and replicate in the nucleus. Phycodnaviridae play important ecological roles by regulating the growth and productivity of their algal hosts. Algal species such Heterosigma akashiwo and the genus Chrysochromulina can form dense blooms which can be damaging to fisheries, resulting in losses in the aquaculture industry. Heterosigma akashiwo virus (HaV) has been suggested for use as a microbial agent to prevent the recurrence of toxic red tides produced by this algal species. Phycodnaviridae cause death and lysis of freshwater and marine algal species, liberating organic carbon, nitrogen and phosphorus into the water, providing nutrients for the microbial loop.

<span class="mw-page-title-main">Bacteriophage MS2</span> Species of virus

Bacteriophage MS2, commonly called MS2, is an icosahedral, positive-sense single-stranded RNA virus that infects the bacterium Escherichia coli and other members of the Enterobacteriaceae. MS2 is a member of a family of closely related bacterial viruses that includes bacteriophage f2, bacteriophage Qβ, R17, and GA.

<span class="mw-page-title-main">Virus</span> Infectious agent that replicates in cells

A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 11,000 of the millions of virus species have been described in detail. The study of viruses is known as virology, a subspeciality of microbiology.

<span class="mw-page-title-main">Sputnik virophage</span>

Mimivirus-dependent virus Sputnik is a subviral agent that reproduces in amoeba cells that are already infected by a certain helper virus; Sputnik uses the helper virus's machinery for reproduction and inhibits replication of the helper virus. It is known as a virophage, in analogy to the term bacteriophage.

<i>Cafeteria roenbergensis virus</i> Species of virus

Cafeteria roenbergensis virus (CroV) is a giant virus that infects the marine bicosoecid flagellate Cafeteria roenbergensis, a member of the microzooplankton community.

Tristromaviridae is a family of viruses. Archaea of the genera Thermoproteus and Pyrobaculum serve as natural hosts. Tristromaviridae is the sole family in the order Primavirales. There are two genera and three species in the family.

This glossary of virology is a list of definitions of terms and concepts used in virology, the study of viruses, particularly in the description of viruses and their actions. Related fields include microbiology, molecular biology, and genetics.

Spiraviridae is a family of incertae sedis viruses that replicate in hyperthermophilic archaea of the genus Aeropyrum, specifically Aeropyrum pernix. The family contains one genus, Alphaspiravirus, which contains one species, Aeropyrum coil-shaped virus. The virions of ACV are non-enveloped and in the shape of hollow cylinders that are formed by a coiling fiber that consists of two intertwining halves of the circular DNA strand inside a capsid. An appendage protrudes from each end of the cylindrical virion. The viral genome is ssDNA(+) and encodes for significantly more genes than other known ssDNA viruses. ACV is also unique in that it appears to lack its own enzymes to aid replication, instead likely using the host cell's replisomes. ACV has no known relation to any other archaea-infecting viruses, but it does share its coil-like morphology with some other archaeal viruses, suggesting that such viruses may be an ancient lineage that only infect archaea.

<span class="mw-page-title-main">Virome</span>

Virome refers to the assemblage of viruses that is often investigated and described by metagenomic sequencing of viral nucleic acids that are found associated with a particular ecosystem, organism or holobiont. The word is frequently used to describe environmental viral shotgun metagenomes. Viruses, including bacteriophages, are found in all environments, and studies of the virome have provided insights into nutrient cycling, development of immunity, and a major source of genes through lysogenic conversion. Also, the human virome has been characterized in nine organs of 31 Finnish individuals using qPCR and NGS methodologies.

<i>Red deerpox virus</i> Species of virus

Red deerpox virus (RDPV) is a species of virus in the genus Parapoxvirus. It has been reported in deer in New Zealand, and in wild ruminants in Italy.

<i>Tupanvirus</i> Proposed genus of viruses

Tupanvirus is a genus of viruses first described in 2018. The genus is composed of two species of virus that are in the giant virus group. Researchers discovered the first isolate in 2012 from deep water sediment samples taken at 3000m depth off the coast of Brazil. The second isolate was collected from a soda lake in Southern Nhecolândia, Brazil in 2014. They are named after Tupã (Tupan), a Guaraní thunder god, and the places they were found. These are the first viruses reported to possess genes for amino-acyl tRNA synthetases for all 20 standard amino acids.

<span class="mw-page-title-main">Marine viruses</span> Viruses found in marine environments

Marine viruses are defined by their habitat as viruses that are found in marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. Viruses are small infectious agents that can only replicate inside the living cells of a host organism, because they need the replication machinery of the host to do so. They can infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea.

<span class="mw-page-title-main">Archaeal virus</span>

An archaeal virus is a virus that infects and replicates in archaea, a domain of unicellular, prokaryotic organisms. Archaeal viruses, like their hosts, are found worldwide, including in extreme environments inhospitable to most life such as acidic hot springs, highly saline bodies of water, and at the bottom of the ocean. They have been also found in the human body. The first known archaeal virus was described in 1974 and since then, a large diversity of archaeal viruses have been discovered, many possessing unique characteristics not found in other viruses. Little is known about their biological processes, such as how they replicate, but they are believed to have many independent origins, some of which likely predate the last archaeal common ancestor (LACA).

Virosphere was coined to refer to all those places in which viruses are found or which are affected by viruses. However, more recently virosphere has also been used to refer to the pool of viruses that occurs in all hosts and all environments, as well as viruses associated with specific types of hosts, type of genome or ecological niche.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Berliner, Aaron J.; Mochizuki, Tomohiro; Stedman, Kenneth M. (2018-01-10). "Astrovirology: Viruses at Large in the Universe". Astrobiology. 18 (2): 207–223. Bibcode:2018AsBio..18..207B. doi:10.1089/ast.2017.1649. ISSN   1531-1074. PMID   29319335. S2CID   4348200.
  2. 1 2 3 Griffin, Dale Warren (August 2013). "The Quest for Extraterrestrial Life: What About the Viruses?". Astrobiology. 13 (8): 774–783. Bibcode:2013AsBio..13..774G. doi:10.1089/ast.2012.0959. ISSN   1531-1074. PMID   23944293.
  3. ↑ Rooney, Bridgette V.; Crucian, Brian E.; Pierson, Duane L.; Laudenslager, Mark L.; Mehta, Satish K. (2019). "Herpes Virus Reactivation in Astronauts During Spaceflight and Its Application on Earth". Frontiers in Microbiology. 10: 16. doi: 10.3389/fmicb.2019.00016 . ISSN   1664-302X. PMC   6374706 . PMID   30792698.
  4. ↑ Gilbert, Rachel; Torres, Medaya; Clemens, Rachel; Hateley, Shannon; Hosamani, Ravikumar; Wade, William; Bhattacharya, Sharmila (2020-02-04). "Spaceflight and simulated microgravity conditions increase virulence of Serratia marcescens in the Drosophila melanogaster infection model". npj Microgravity. 6 (1): 4. Bibcode:2020npjMG...6....4G. doi:10.1038/s41526-019-0091-2. ISSN   2373-8065. PMC   7000411 . PMID   32047838.
  5. ↑ van Heereveld, Luc; Merrison, Jonathan; Nørnberg, Per; Finster, Kai (June 2017). "Assessment of the Forward Contamination Risk of Mars by Clean Room Isolates from Space-Craft Assembly Facilities through Aeolian Transport - a Model Study". Origins of Life and Evolution of the Biosphere. 47 (2): 203–214. Bibcode:2017OLEB...47..203V. doi:10.1007/s11084-016-9515-0. ISSN   1573-0875. PMID   27461254. S2CID   8676082.
  6. ↑ Bashir, Mina; Ahmed, Mahjabeen; Weinmaier, Thomas; Ciobanu, Doina; Ivanova, Natalia; Pieber, Thomas R.; Vaishampayan, Parag A. (2016-09-09). "Functional Metagenomics of Spacecraft Assembly Cleanrooms: Presence of Virulence Factors Associated with Human Pathogens". Frontiers in Microbiology. 7: 1321. doi: 10.3389/fmicb.2016.01321 . ISSN   1664-302X. PMC   5017214 . PMID   27667984.
  7. ↑ Weinmaier, Thomas; Probst, Alexander J.; La Duc, Myron T.; Ciobanu, Doina; Cheng, Jan-Fang; Ivanova, Natalia; Rattei, Thomas; Vaishampayan, Parag (2015-12-08). "A viability-linked metagenomic analysis of cleanroom environments: eukarya, prokaryotes, and viruses". Microbiome. 3: 62. doi: 10.1186/s40168-015-0129-y . ISSN   2049-2618. PMC   4672508 . PMID   26642878.
  8. ↑ "Electron Microscopy | TEM vs SEM - US". www.thermofisher.com. Retrieved 2021-02-21.
  9. 1 2 Janjic, Aleksandar (2018-11-29). "The Need for Including Virus Detection Methods in Future Mars Missions". Astrobiology. 18 (12): 1611–1614. Bibcode:2018AsBio..18.1611J. doi:10.1089/ast.2018.1851. ISSN   1531-1074. S2CID   105299840.
  10. ↑ mars.nasa.gov. "Sample Handling". mars.nasa.gov. Retrieved 2021-02-21.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.