Chlorovirus

' Chlorovirus'
Systematics
Classification : Viruses Area : Varidnaviria Empire : Bamfordvirae Phylum : Nucleocytoviricota Class : Megaviricetes Order : Algavirales Family : Phycodnaviridae Genre : Chlorovirus
Taxonomic characteristics
Genome : dsDNA linear Baltimore : Group 1 Cover : available
Scientific name
Chlorovirus
Left
NCBI  Taxonomy: 181083 ViralZone ( ExPASy , SIB): 588

Chlorovirus , also known as Chlorellavirus , is a genus of viruses with a double-stranded DNA genome in the Phycodnaviridae family. It belongs to the Phylum Nucleocytoviricota (alias Nucleocytoplasmic large DNA viruses , NCLDV).

This genus is found in freshwater environments around the world, where microscopic algae serve as natural hosts. There are currently 19 species in this genus, including the type species Paramecium bursaria Chlorella virus 1 . The word component chloro- is derived from the Greek  χλωρός chlōrós: "yellowish", "green".

The chlorovirus was discovered in 1981 by Russel H. Meintz, James L. Van Etten, Daniel Kuczmarski, Kit Lee and Barbara Ang while trying to cultivate algae similar to Chlorella . During the procedure, virus particles (virions) were detected in the cells 2 to 6 hours after the initial isolation, followed by lysis (death by disintegration of the host cell) after 12 to 20 hours. This virus is referred to as HVCV-1 ( Hydra viridis Chlorella virus 1 ) because living unicellular green algae ( zoochlorella ) have been infected in the freshwater polyp Hydra viridis . Some time ago, a species commonly found in lakes, ATCV-1 ( Acanthocystis turfacea chlorella virus 1 ), was found to infect humans as well. More detailed investigations are still necessary. More recent studies of the effects of infections in the mouse model followed.

Systematics

Internal system

The International Committee on Taxonomy of Viruses (ICTV) recognized the following species as of November 2018:

• Genus: Chlorovirus

• Species Acanthocystis turfacea chlorella virus 1 (ATCV-1, ATCV1)
• Species Hydra viridis Chlorella virus 1 (HVCV-1)
• Species Paramecium bursaria Chlorella virus 1 (PBCV-1, type species)
• Species Paramecium bursaria Chlorella virus A1 (PBCV-A1)
• Species Paramecium bursaria Chlorella virus AL1A (PBCV-AL1A)
• Species Paramecium bursaria Chlorella virus AL2A (PBCV-AL2A)
• Species Paramecium bursaria Chlorella virus BJ2C (PBCV-BJ2C)
• Species Paramecium bursaria Chlorella virus CA4A (PBCV-CA4A)
• Species Paramecium bursaria Chlorella virus CA4B (PBCV-CA4B)
• Species Paramecium bursaria Chlorella virus IL3A (PBCV-IL3A)
• Species Paramecium bursaria Chlorella virus NC1A (PBCV-NC1A)
• Species Paramecium bursaria Chlorella virus NE8A (PBCV-NE8A)
• Species Paramecium bursaria Chlorella virus NY2A (PBCV-NY2A)
• Species Paramecium bursaria Chlorella virus NYs1 (PBCV-NYs1)
• Species Paramecium bursaria Chlorella virus SC1A (PBCV-SC1A)
• Species Paramecium bursaria Chlorella virus XY6E (PBCV-XY6E)
• Species Paramecium bursaria Chlorella virus XZ3A (PBCV-XZ3A)
• Species Paramecium bursaria Chlorella virus XZ4A (PBCV-XZ4A)
• Species Paramecium bursaria Chlorella virus XZ4C (PBCV-XZ4C)

Other suggested species are:

• Species ' Paramecium bursaria Chlorella virus MT325 ' (PBCV-MT325)>
• Species ' Paramecium bursaria Chlorella virus CVK2 ' (PBCV-CVK2)
• Species ' Paramecium bursaria Chlorella virus AR158 ' (PBCV-AR158)
• Species ' Paramecium bursaria Chlorella virus FR483 ' (PBCV-FR483)
• Species ' Chlorella variabilis Virus NC64A ' (see below)
• Species ' Chlorella variabilis Virus Syngen ' (see below)
• Species' Chlorella heliozoae 'Virus SAG ' (see below)
• Species ' Only Syngen Nebraska virus 5 '
• Species ' Acanthocystis turfacea Chlorella virus TN603 ' (ATCV-TN603)

Phylogenetic tree according to Hao et al. (2018):

Chlorovirus	Acanthocystis turfacea chlorella virus 1 (ATCV1)     Paramecium bursaria chlorella virus A1 (PBCV CVA-1)     Paramecium bursaria chlorella virus 1 (PBCV1)     Paramecium bursaria chlorella virus NY2 (PBCV-NY2A)     Paramecium bursaria chlorella virus NYs1 (PBCV NYs1)

External system

The following system follows Schulz et al. (2018) with corrections and additions according to Hao et al. (2018):

Phycodnaviridae	Chlorovirus type  Chlorovirus     YSLPV1, YSLPV2     DSLPV1     Prasinovirus     Phaeovirus     Mollivirus     Pandora Viruses     ' Sylvan virus '     Coccolithovirus

ecology

Chloroviruses are widespread in freshwater environments in all parts of the world and have been isolated from freshwater sources in Europe, Asia, Australia, and North and South America.

Hosts

The natural hosts of chloroviruses include various types of unicellular Chlorella -like algae called zoochlorella . They are very species and even strain specific: individual virus species typically only infect hosts of a certain line ( strain ). These zoochlorella generally build endosymbiotic relationships with larger protozoa ( protists ) and invertebrates (invertebrata) in fresh or salt water, for example:

• the green paramecium ( Paramecium bursaria , an eyelash animal - Ciliophora),
• the green hydra ( Hydra viridissima alias H. viridis , Hydrozoa ),
• Acanthocystis turfacea ( Hacrobia : Centroheliozoa , outdated ' sun animals ', see also Acanthocystis turfacea on Microworld).

While a single protist can harbor up to several hundred algal cells at any given time, free-floating algae are very susceptible to chloroviruses, suggesting that such endosymbiosis confers resistance to infection.

Chloroviruses have also recently been found to infect humans. The possibility of infection in mice is being investigated.

Occurrence

Chlorovirus titers vary depending on the time of year and location. Due to the rich genetic diversity and the high degree of specialization of individual virus species, deviations in their ecology are not unusual. This leads to specific spatio-temporal patterns that ultimately depend on the lifestyle and the type of host. Previous overview data showed two prominent seasonal frequency peaks : for Chlorella variabilis NC64A virus in late autumn and for Chlorella variabilis syngen virus in late spring to mid-summer, probably due to the fact that they share the host. Conversely, Chlorella heliozoae SAG viruses peaked at different times of the year and generally exhibited greater variability in titers compared to the NC64A and Syngen viruses.

In addition, studies have shown that chloroviruses have some resistance to winter temperature drops, as evidenced by the presence of infectious particles (virions) under layers of ice in a rainwater management pond in Ontario , Canada . DeLong, et al. 2016 suggest that persecution by small crustaceans ( crustaceans can play an indirect role in Titerfluktuation). The breakdown of protist cells that pass through the digestive tract of the crustaceans could lead to the release of a large number of unicellular algae, which - due to the omitted end symbiotic host - become susceptible to viral infection. As a consequence, the seasonal frequency of chloroviruses depends not only on the host species, but also on many other microorganisms, the general nutrient status and ecological framework conditions.

As a whole, chloroviruses can influence global biogeochemical cycles through phytoplankton turnover. It is known that chlorella, together with other types of microscopic algae and blue-green bacteria (cyanobacteria) such as Microcystis aeruginosa, causes toxic algal blooms , which in the northern hemisphere (half of the earth) usually last from February to June. This leads to a lack of oxygen and consequently to the death of larger organisms in the freshwater habitats .

Lytic (i.e., cell-destroying) infection of unicellular algae by chloroviruses leads to the breakdown of the algal blooms and subsequent release of the carbon , nitrogen and phosphorus contained in the algal cells , which are ultimately diluted and returned to the food chain.

construction

The virions of the genus Chlorovirus have an envelope with icosahedral or spherical geometry and a symmetry ( triangulation number ) T = 169 . The diameter is approx. 100–220 nm. The genome is linear, usually simply present and consists of double-stranded DNA ( dsDNA ) with a length of approx. 330  kb . The dsDNA is closed with a hairpin (hairpin structure) at the end. There are often several hundred ORFs (open reading frames).

The chlorovirus genus in its entirety codes for a total of 632 protein families, but each individual virus only has 330-416 genes that code for proteins. Chloroviruses have methylated bases in certain sections of their DNA sequence . Some chloroviruses also contain introns and inteins , although this is rare within the genus.

• The type species Paramecium bursaria Chlorella virus 1 (PBCV-1) has a diameter of 190 nm and a five-fold axis. The junction of its head has a protruding spine, this is the first part of the virion to contact its host. The outer capsid covers a single membrane made up of a lipid bilayer obtained from the host's endoplasmic reticulum .

The genome length is 330,611 bp, with 802 proteins being predicted to be encoded . The GC content is 40%. Some capsomeres on the outer shell have fibers that protrude from the virus particle and support attachment to the host (cf. Mimivirus ).

• The species Acanthocystis turfacea Chlorella virus 1 (AtCV-1) has a genome length of 288,047 bp, 860 proteins are predicted to be encoded and the GC content is 49%.

Propagation cycle

In Paramecium bursaria chlorella virus 1 (PBCV-1), the prototype of the chlorovirus, the spine first touches the host's cell wall . and is then supported by fibers to secure the virus pond (virion) on the host. The attachment of PBCV-1 to its receptor is very specific and severely limits the range of possible hosts. Virus-associated enzymes enable the host cell wall to be broken down and the internal membrane of the virus fuses with the host membrane. This fusion enables the transfer of viral DNA and viral proteins into the host cell and also triggers depolarization of the host membrane.

Chlorella cells and Paramecium bursaria Chlorella virus 1 (PBCV-1)

Since PBCV-1 does not have a gene for RNA polymerase , its DNA and viral proteins migrate into the cell nucleus, where transcription begins 5–10 minutes after infection. It is believed that this rapid transcription is made possible by a protein that transfers DNA into the cell nucleus and is encoded by the PBCV-a443r gene . It is similar to proteins that are involved in shipping through the nuclear membrane in mammalian cells.

In this early phase of infection, the host's (own) transcription rate decreases and the host's transcription components are reprogrammed to transcribe the new viral DNA. Minutes after infection, the host's chromosomal DNA begins to break down . It is believed that this is done by PBCV-1 encoded and packaged DNA restriction endonucleases . As a result of the breakdown of the host chromosomal DNA, the host's transcription comes to a standstill. This results in 33-55% of polya.

Viral DNA replication begins after 60 to 90 minutes. The assembly of the virus envelopes ( capsids ) begins about 2-3 hours after infection . This occurs in localized regions of the cytoplasm, with the viral capsids being observable 3-4 hours after the initial infection. 5-6 hours after PBCV-1 infection, the host cell's cytoplasm fills with infectious virus particles (the progeny). Shortly thereafter (6-8 hours after infection), localized lysis (disintegration) of the host cell releases these progeny. Approx. 1000 virus particles are released from each infected cell.

Infection in humans

Recently, chlorovirus ATCV-1 DNA was found in human pharynx samples. To date, it was not known that the chlorovirus could infect humans, so knowledge about infections in humans is still very limited. Infected individuals had delayed memory and attention, and decreased visual processing and motor skills. Overall, this led to a decline in the ability to perform tasks based on vision and spatial reasoning.

The studies on the infection of mice with ATCV-1 showed changes in the Cdk5 signaling pathway, which supports learning and memory formation, as well as changes in gene expression in the dopamine signaling pathway in infected animals . Infected mice also turned out to be less social and interacted less with newly introduced companion mice than the healthy control group. They spent extended periods of time in a light-exposed area of ​​the test chamber, whereas the control mice preferred the dark side as usual and avoided the light. This indicates a decrease in anxiety with ATCV-1 infection. The test mice were also less able to recognize an object that had been moved from its previous position, which shows a decrease in the spatial reference memory. As with humans, the spatial task of the visual center decreases.

literature

• Dickson Kinyanyi, George Obiero, Peris W Amwayi, Stephen Mwaniki, Mark Wamalwa: In silico structural and functional prediction of African swine fever virus protein-B263R reveals features of a TATA-binding protein , in: PeerJ 6 (4): e4396 (2018 ), doi: 10.7717 / peerj.4396 , p. 13, especially Fig. 7
• Weijia Zhang, Jinglie Zhou, Taigang Liu, Yongxin Yu, Yingjie Pan, Shuling Yan, Yongjie Wang: Four novel algal virus genomes discovered from Yellowstone Lake metagenomes , in: Scientific Reports volume 5, Article No. 15131, 2015, doi: 10.1038 / srep15131 , abstract

Web links

• Viral zone : chlorovirus
• ICTV

Individual evidence

1. ↑ ^{a b c d e} ICTV: ICTV Master Species List 2019.v1 , New MSL including all taxa updates since the 2018b release, March 2020 (MSL # 35)
2. ↑ Yutin N, Wolf YI, Koonin EV: Origin of giant viruses from smaller DNA viruses not from a fourth domain of cellular life . In: Virology . 466–467, October 2014, pp. 38–52. doi : 10.1016 / j.virol.2014.06.032 . PMID 25042053 . PMC 4325995 (free full text).
3. ↑ Dunigan DD, Fitzgerald LA, Van Etten JL: Phycodnaviruses: a peek at genetic diversity . In: Virus Research . 117, No. 1, April 2006, pp. 119-32. doi : 10.1016 / j.virusres.2006.01.024 . PMID 16516998 .
4. ↑ ^{a b} Viral Zone . ExPASy. Retrieved December 23, 2018.
5. ^ ICTV: Virus Taxonomy . Retrieved December 22, 2015.
6. ↑ ICTV Master Species List 2018a v1 , ICTV MSL including all taxa updates since the 2017 release.
7. ↑ Russel H. Meints, James L. Van Etten, Daniel Kuczmarski, Kit Lee, Barbara Ang: Viral infection of the symbiotic chlorella-like alga present in Hydra viridis . In: Virology . 113, No. 2, September 1981, pp. 698-703. PMID 18635088 .
8. ↑ Ryo Hoshina, Mayumi Shimizu, Yoichi Makino, Yoshihiro Haruyama, Shin-ichiro Ueda, Yutaka Kato, Masahiro Kasahara, Bun-ichiro Ono, Nobutaka Imamura: Isolation and characterization of a virus (CvV-BW1) that infectsaria symbiotic algae of Paramecium in Lake Biwa, Japan . In: Virology Journal . 7, September 13, 2010, ISSN  1743-422X , p. 222. doi : 10.1186 / 1743-422X-7-222 . PMID 20831832 . PMC 2949830 (free full text).
9. ↑ ^{a b c d e f} Yolken RH, Jones-Brando L, Dunigan DD, Kannan G, Dickerson F, Severance E, Sabunciyan S, Talbot CC, Prandovszky E, Gurnon JR, Agarkova IV, Leister F, Gressitt KL, Chen O , Deuber B, Ma F, Pletnikov MV, Van Etten JL: Chlorovirus ATCV-1 is part of the human oropharyngeal virome and is associated with changes in cognitive functions in humans and mice . In: Proceedings of the National Academy of Sciences of the United States of America . 111, No. 45, November 2014, pp. 16106-11. doi : 10.1073 / pnas.1418895111 . PMID 25349393 . PMC 4234575 (free full text).
10. ^ ^{A b c} Marilyn S. Petro, Irina V. Agarkova, Thomas M. Petro: Effect of Chlorovirus ATCV-1 infection on behavior of C57Bl / 6 mice . In: Journal of Neuroimmunology . 297, August 2016, pp. 46–55. doi : 10.1016 / j.jneuroim.2016.05.009 . PMID 27397075 .
11. ↑ William H Wilson, Ilana C Gilg, Mohammad Moniruzzaman, Erin K Field, Sergey Koren, Gary R LeCleir, Joaquín Martínez Martínez, Nicole J Poulton, Brandon K Swan, Ramunas Stepanauskas, Steven W Wilhelm: Genomic exploration of individual giant ocean viruses , in: ISME Journal 11 (8), August 2017, pp. 1736–1745, doi: 10.1038 / ismej.2017.61 , PMC 5520044 (free full text), PMID 28498373 . Apparently mistakenly referred to here as Acanthamoeba turfacea Chlorella virus (ATCV).
12. ↑ ^{a b c d e f g} Hao Chen, Weijia Zhang, Xiefei Li, Yingjie Pan, Shuling Yan, Yongjie Wang: The genome of a prasinoviruses-related freshwater virus reveals unusual diversity of phycodnaviruses , in: BMC Genomics, December 2018, 19 : 49 (online January 15, 2018), doi: 10.1186 / s12864-018-4432-4
13. ↑ ^{a b c d e f g h} Guillaume Blanc, Garry Duncan, Irina Agarkova, Mark Borodovsky, James Gurnon, Alan Kuo, Erika Lindquist, Susan Lucas, Jasmyn Pangilinan, Juergen Polle, Asaf Salamov, Astrid Terry, Takashi Yamada, David D Dunigan, Igor V. Grigoriev, Jean-Michel Claverie, James L. Van Etten: The Chlorella variabilis NC64A genome reveals adaptation to photosymbiosis, coevolution with viruses, and cryptic sex , in: Plant Cell 22, 2010, pp. 2943-2955 , doi: 10.1105 / tpc.110.076406
14. ↑ ^{a b} Julien Andreani, Jacques YB Khalil, Emeline Baptiste, Issam Hasni, Caroline Michelle, Didier Raoult, Anthony Levasseur, Bernard La Scola: Orpheovirus IHUMI-LCC2: A New Virus among the Giant Viruses , in: Front. Microbiol., January 22, 2018, doi: 10.3389 / fmicb.2017.02643
15. ↑ NCBI: Paramecium bursaria Chlorella virus AR158 (Species)
16. ↑ NCBI: Paramecium bursaria Chlorella virus FR483 (Species)
17. ↑ NCBI: Only Syngen Nebraska virus 5 (Species)
18. ↑ NCBI: Acanthocystis turfacea Chlorella virus TN603.4.2 (Species)
19. ↑ Frederik Schulz, Lauren Alteio, Danielle Goudeau, Elizabeth M. Ryan, Feiqiao B. Yu, Rex R. Malmstrom, Jeffrey Blanchard, Tanja Woyke: Hidden diversity of soil giant viruses , in: Nature Communicationsvolume 9, Article number: 4881 (2018 ) from November 19, 2018, doi: 10.1007 / s00705-016-2853-4
20. ↑ Fumito Maruyama, Shoko Ueki: Evolution and Phylogeny of Large DNA Viruses, Mimiviridae and Phycodnaviridae Including Newly Characterized Heterosigma akashiwo Virus. In: Front. Microbiol. November 30, 2016, doi: 10.3389 / fmicb.2016.01942 , PMC 5127864 (free full text), PMID 27965659 .
21. ↑ ^{a b} Quispe CF, Sonderman O, Seng A, Rasmussen B, Weber G, Mueller C, Dunigan DD, Van Etten JL: Three-year survey of abundance, prevalence and genetic diversity of chlorovirus populations in a small urban lake . In: Archives of Virology . 161, No. 7, July 2016, pp. 1839-47. PMID 27068168 .
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23. ↑ ^{a b c d} James L. Van Etten, David D. Dunigan, Richard C. Condit: Giant Chloroviruses: Five Easy Questions . In: PLOS Pathogens . 12, No. 8, August 18, 2016, p. E1005751. doi : 10.1371 / journal.ppat.1005751 . PMID 27536965 . PMC 4990331 (free full text).
24. ↑ ^{a b c d e} James L. Van Etten, David D. Dunigan: Chloroviruses: not your everyday plant virus . In: Trends in Plant Science . 17, No. 1, January 2012, pp. 1-8. doi : 10.1016 / j.tplants.2011.10.005 . PMID 22100667 . PMC 3259250 (free full text).
25. ↑ ^{a b} DeLong JP, Al-Ameeli Z, Duncan G, Van Etten JL, Dunigan DD: Predators catalyze an increase in chloroviruses by foraging on the symbiotic hosts of zoochlorellae . In: Proceedings of the National Academy of Sciences of the United States of America . 113, No. 48, November 2016, pp. 13780-13784. doi : 10.1073 / pnas.1613843113 . PMID 27821770 . PMC 5137705 (free full text).
26. ↑ Long AM, Short SM: Seasonal determinations of algal virus decay rates reveal overwintering in a temperate freshwater pond . In: The ISME Journal . 10, No. 7, July 2016, pp. 1602-12. doi : 10.1038 / ismej.2015.240 . PMID 26943625 . PMC 4918447 (free full text).
27. ↑ ^{a b} Yanai GM: Transcription analysis of the chlorovirus Paramecium bursaria chlorella virus-1 (PhD). University of Nebraska at Lincoln, 2009.
28. ↑ Song H, Lavoie M, Fan X, Tan H, Liu G, Xu P, Fu Z, Paerl HW, Qian H: Allelopathic interactions of linoleic acid and nitric oxide increase the competitive ability of Microcystis aeruginosa . In: The ISME Journal . 11, No. 8, August 2017, pp. 1865–1876. doi : 10.1038 / ismej.2017.45 . PMID 28398349 . PMC 5520033 (free full text).
29. ^ Rieper M: Investigations on the relationships between algal blooms and bacterial populations in the Schlei Fjord (western Baltic Sea) . In: Helgoland scientific marine studies . 28, No. 1, March 1, 1976, pp. 1-18. doi : 10.1007 / BF01610792 .
30. ↑ ^{a b} Cristian F. Quispe, Ahmed Esmael, Olivia Sonderman, Michelle McQuinn, Irina Agarkova, Mohammed Battah, Garry A. Duncan, David D. Dunigan, Timothy PL Smith, Cristina De Castro, Immacolata Speciale, Fangrui Ma, James L. Van Etten: Characterization of a new chlorovirus type with permissive and non-permissive features on phylogenetically related algal strains . In: Virology . 500, January 2017, pp. 103-113. doi : 10.1016 / j.virol.2016.10.013 . PMID 27816636 . PMC 5127778 (free full text).
31. ↑ ^{a b} David M. Needham, Alexandra Z. Worden et al .: A distinct lineage of giant viruses brings a rhodopsin photosystem to unicellular marine predators , in: PNAS, 23 September 2019, doi: 10.1073 / pnas.1907517116 , ISSN 0027 -8424, here: Supplement 1 (xlsx)
32. ↑ Jean-Michel Claverie, Chantal Abergel: ["Mimiviridae": An Expanding Family of Highly Diverse Large dsDNA Viruses Infecting a Wide Phylogenetic Range of Aquatic Eukaryotes]. In: Viruses . 2018 Sep; 10 (9), September 18, 2018, p. 506, doi: 10.3390 / v10090506 , PMC 6163669 (free full text), PMID 30231528 , Tab. 2
33. ↑ Zhang X, Xiang Y, Dunigan DD, Klose T, Chipman PR, Van Etten JL, Rossmann MG: Three dimensional structure and function of the Paramecium bursaria chlorella virus capsid. Proc. Natl. Acad. Sci. USA 2011, 108, pp. 14837-14842 , doi: 10.1073 / pnas.1107847108 , PMID 21873222
34. ↑ Blanc G, Mozar M, Agarkova IV, Gurnon JR, Yanai Balser G, Rowe JM, Xia Y, Riethoven JJ, Dunigan DD, Van Etten JL: Deep RNA sequencing reveals hidden features and dynamics of early gene transcription in Paramecium bursaria chlorella virus 1. PLoS ONE 2014, 9: e90989, doi: 10.1371 / journal.pone.0090989 , PMID 24608750
35. ↑ See also Jerry H.-C. Wang