Microviridae

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Microviridae
Systematics
Classification : Viruses
Area : Monodnaviria
Empire : Sangervirae
Phylum : Phixviricota
Class : Malgrandaviricetes
Order : Petitviral
Family : Microviridae
Taxonomic characteristics
Genome : (+) ssDNA circular
Baltimore : Group 2
Symmetry : icosahedral
Cover : no
Scientific name
Microviridae
Left
NCBI  Taxonomy: 10841
ViralZone ( ExPASy , SIB): 114
ICTVdB Virus Code : 00.042

The Microviridae (from the Greek μικρός - mikrós : small) are a family of viruses that, as bacteriophages, infect various bacteria , including representatives of the Enterobacteriaceae and intracellular parasitic bacteria as well as spiroplasma . Due to their host range , the Microviridae are ubiquitous in sewage , soil or faeces . The first and best characterized species of the family is the enterobacteriophage PhiX174 (formerly called Coliphage φX174 ).

morphology

The virions (virus particles) of the Microviridae consist of a simple, icosahedral capsid ( T = 1 ), which are made up of three or four different capsid proteins . The unenveloped capsids have a diameter of 25 to 27 nanometers . The mature virions arise from intracellular precursor capsids (procapsids), in which one or two structural proteins ( scaffolding proteins , "framework proteins") enable the binding of the DNA and the assembly of the capsomeres through a coarse, preliminary framework . During the maturation of the capsid, these framework proteins are released from the association again as soon as the main capsid proteins have assumed an icosahedral arrangement and the capsid is closed. The main components of the capsids consist of a spike protein and a capsid protein (F or Vp1), which combine to form large five-pointed capsomeres ( pentamers ). The 5.4 nm (with Enterobacteriophage PhiX174 ) protruding far outward spike proteins mediate the specific attachment and uptake in the bacterial cell.

The capsids of the genera Bdellomicrovirus and Chlamydiamicrovirus show a specific density of 1.30 to 1.31 g / cm³ in ultracentrifugation with cesium chloride , while the representatives of the other two genera all have a significantly higher density of about 1.40 g / cm³. The virions are very environmentally stable at pH values between 6.0 and 9.0 and can not be inactivated with detergents , 2-propanol or chloroform .

Genome

The microviridae having as genome a ring-closed (circular) single stranded ( English single stranded ) DNA molecule with a positive polarity . In the subfamily Bullavirinae it comprises between 5,300 and 6,100 nucleotides , the other genera have significantly smaller genomes with 4,400 to 4,900 nucleotides. The arrangement of the four largest open reading frames (ORF) is uniform within the family; they are usually separated from one another by short, non-coding sections. In addition, there are various ORFs that are embedded in the large reading frames with other reading frames. The replication of the genome in the Microviridae takes place via a double-stranded DNA intermediate stage, but the details of the replication between the genera are very different. In the case of the Microviridae , a horizontal gene transfer has been described which has produced a greater variability of the genomes within the virus family and which occurs to a much greater extent than in double-stranded DNA bacteriophages. The chromosome of the enterobacteriophage PhiX174 was the first DNA molecule that was completely sequenced before the simian virus 40 (SV40 or MmPV1) and the plasmid pBR322 .

Biological importance

Viruses of the subfamily Bullavirinae infect enterobacteria , which also include Escherichia coli and Salmonella enterica . Species of the genus Bdellomicrovirus have bacteria of the genus Bdellovibrio as host cells. This host spectrum thus includes gram-negative , aerobic bacteria in both genera . The other two genera infect different groups of intracellularly reproducing bacteria: representatives of the genus Clamydiamicrovirus parasitize in chlamydia , those of the genus Spiromicrovirus in the bacterial genus Spiroplasma from the class of the cell wallless Mollicutes (order Entomoplasmatales ), which in turn parasitize in small mammals and insects.

Systematics

According to ICTV, the family Microviridae is divided into two subfamilies of three genera each as of November 2018, whereby the subfamily Bullavirinae (formerly the genus Microvirus ) differs significantly from the other subfamily Gokushovirinae in its hosts and genome organization. Viruses of the subfamily Bullavirinae infect enterobacteria , while Gokushoviruses infect intracellular parasites. The name Bullavirinae comes from the Latin word bulla (boss, button, pen), the name Gokushovirinae is derived from Japanese for 'very small' ( Kanji : 極小Hiragana : ご く し ょ う のgókushō (no) microscopic, tiny, minimal).

Alpavirinae , whose viruses infect the order Bacteroidales , have been proposed as a possible third subfamily . The name comes from the Sanskrit word अल्प (álpa) for small, mini. This is a group of viruses previously known only as prophages , and further research on these viruses is needed before ICTV can grant subfamily status.

Pichovirinae was suggested as a possible fourth subfamily . The members of this group have a genomic organization that is different from the others in the Microviridae family . The name is derived from the Occitan word 'picho' for 'small'.

Another virus ( Microphage ΦCA82 ) was isolated from the intestines of turkeys and has now been located in the vicinity of Spiroplasma virus SpV4 .

The system according to ICTV as of November 2018, supplemented by the above suggestions, is as follows:

literature

  • B. Fane: Family Microviridae . In: CM Fauquet, MA Mayo et al .: Eighth Report of the International Committee on Taxonomy of Viruses . London / San Diego 2005 pp. 289ff ISBN 0-12-249951-4
  • GN Godson: The other isometric phages. In: DT Denhardt, D. Dressler, DS Ray (Eds.): The single-stranded DNA phages. Cold Spring Harbor Laboratory Press, Cold Spring Harbor NY 1978, pp. 103-112

Web links

Individual evidence

  1. ↑ a b c d e ICTV: ICTV Taxonomy history: Escherichia virus phiX174 , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
  2. ↑ Viral Zone . ExPASy. Retrieved December 15, 2018.
  3. ^ ICTV: Virus Taxonomy . Retrieved December 15, 2018.
  4. ↑ T. Dokland et al. : Structure of a viral procapsid with molecular scaffolding. Nature (1997) 389 (6648): pp. 308-313 PMID 9305849
  5. ↑ DR Rokyta, CL Burch, SB Caudle, HA Wichman: Horizontal Gene Transfer and the Evolution of Microvirid Coliphage Genomes. In: Journal of Bacteriology , 2006, 188 (3), pp. 1134–1142, PMID 16428417 , PMC 1347346 (free full text)
  6. ↑ F. Sanger, GM Air, BG Barrell, NL Brown, AR Coulson, CA Fiddes, CA Hutchison, PM Slocombe, M. Smith: Nucleotide sequence of bacteriophage phi X174 DNA. In: Nature. Volume 265, Number 5596, February 1977, pp. 687-695, PMID 870828 .
  7. ↑ Approved Proposals> Bacterial and Archaeal Viruses: Bullavirinae , ICTV online 2015.026a-rB.A.v3
  8. ↑ a b M. Krupovic, P. Forterre: Microviridae goes temperate: microvirus-related proviruses reside in the genomes of Bacteroidetes . In: PLoS ONE . 6, No. 5, 2011, p. E19893. doi : 10.1371 / journal.pone.0019893 . PMID 21572966 . PMC 3091885 (free full text).
  9. ^ A b Roux S, Krupovic M, Poulet A, Debroas D, Enault F: Evolution and diversity of the Microviridae viral family through a collection of 81 new complete genomes assembled from virome reads . In: PLoS ONE . 7, No. 7, 2012, p. E40418. doi : 10.1371 / journal.pone.0040418 . PMID 22808158 . PMC 3394797 (free full text).
  10. ↑ L Zsak, JM Day, BB Oakley, BS Seal: The complete genome sequence and genetic analysis of ΦCA82 a novel uncultured microphage from the turkey gastrointestinal system . In: Virol J , 8, 2011, p. 331, doi: 10.1186 / 1743-422X-8-331 , PMID 21714899
  11. ↑ a b Lianghua Guo, Xiuguo Hua, Wen Zhang, Shixing Yang, Quan Shen, Haibing Hu, Jingjiao Li, Zhijian Liu, Xiaochun Wang, Hua Wang, Chenglin Zhou, Li Cui: Viral metagenomics analysis of feces from coronary heart disease patients reveals the genetic diversity of the “Microviridae” . In: Vorologic Sinica , April 17, 2017, doi: 10.1007 / s12250-016-3896-0
  12. ^ Roger G. Rank, Anne K. Bowlin, Stefania Cané, Huizhong Shou, Zhi Liu, Uma M. Nagarajan, Patrik M. Bavoil: Effect of Chlamydiaphage φCPG1 on the Course of Conjunctival Infection with Chlamydia caviae in Guinea Pigs . (PDF) In: Infection And Immunity , March 2009, pp. 1216-1221
  13. ↑ a b c Simon J. Labrie, Marie-Ève ​​Dupuis, Denise M. Tremblay, Pier-Luc Plante, Jacques Corbeil, Sylvain Moineau: A New Microviridae Phage Isolated from a Failed Biotechnological Process Driven by Escherichia coli (PDF) in: Journals ASM: Applied and Environmental Microbiology (AEM) Volume 80 No. 22, November 2014, pp. 6992-7000
  14. ↑ Coliphage phi-X174, complete genomeNCBI Reference Sequence: NC_001422.1 , NCBI