Microviridae

The Microviridae (from Greek μικρός: small) are a family of viruses that infect bacteria as different bacteriophages, including representatives of the Enterobacteriaceae and intracellular living bacteria groups. Due to their host range, the Microviridae are ubiquitously present in wastewater, soil or feces. The first and best-characterized species of the family is the Enterobakteriophage φX174 ( formerly known as coliphage φX174 ).

Morphology

The virions consist of a simple Microviridae, icosahedral capsid (T = 1), which are composed of three or four different capsid proteins. The non-enveloped capsids have a diameter 25 to 27 nanometers. Mature virions go from intracellular produced Vorläuferkapsiden ( Prokapside ) in which allow one or two structural proteins ( scaffolding protein " scaffold proteins " ) by a coarse preliminary stand the binding of DNA and assembly of capsomeres. These scaffold proteins are dissolved in the maturation of the capsid again from the Association as soon as the Hauptkapsidproteine ​​have taken an icosahedral arrangement and the capsid is closed. The main components of the capsids consist of a spike protein and a capsid protein ( Vp1 or F ), which assemble into large five-pointed ( pentamers ) capsomeres. The 5.4 nm extending far to the outside ( the Enterobakteriophage ΦX174 ) spike proteins mediate specific attachment and uptake into the bacterial cell.

The capsids of the genera Bdellomicrovirus and Chlamydiamicrovirus show a specific gravity of 1.30 to 1.31 g/cm3 in cesium chloride ultracentrifugation, 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 by detergents, 2-propanol or chloroform.

Genome

The Microviridae own genome as a closed ring ( circular ), single-stranded (german single stranded ) DNA molecule with positive polarity. It includes in the genus Micro Virus 5300-6100 nucleotides, the other species have much smaller genomes 4400-4900 nucleotides. The arrangement of the four major open reading frame ( ORF) is uniform within the family; they are usually separated from each other by short, non-coding sections. In addition, there are various ORFs which are embedded in other reading frames in the major reading frames. The replication of the genome takes place at the Microviridae a double-stranded DNA intermediate, in detail, however, the replication between the genera is very different. The Microviridae a Horizontal gene transfer is described, which has spawned a greater variability of the genomes within the virus family and is present in much greater use than double-stranded DNA bacteriophages.

Biological Significance

Viruses of the genus Micro Virus infect enterobacteria, including Escherichia coli and Salmonella enterica include species of the genus Bdellomicrovirus have bacteria of the genus Bdellovibrio as host cells. So this host range comprises Gram-negative, aerobic bacteria of both genera. The other two genera infect different groups of intracellularly proliferating bacteria: Representatives of the genus Clamydiamicrovirus parasitize chlamydia, those of the genus Spiro Micro Virus in the bacterial genus Spiroplasma from the group of wall-less Mollicutes, which in turn parasitize small mammals and insects.

System

The Microviridae family is currently divided into four genera, with the genus Micro virus in their genome organization differs significantly from the other genera. It is currently debated whether these three genera should be combined into a subfamily or merge into a single genus. For the latter speaks the large phylogenetic proximity of the virus species of these genera.

  • Family Microviridae
  • Genus Bdellomicrovirus
  • Genus Chlamydiamicrovirus
  • Genus Micro Virus
  • Genus Spiro Micro Virus

Swell

  • 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 p 289ff ISBN 0-12-249951-4
  • G. N. Godson: The other isometric phages. In: DT Denhardt, D. Dressler and DS Ray (ed.): The single-stranded DNA phages. Pp. 103-112, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York 1978
Virus classification National Center for Biotechnology Information Virus#Etymology Ultracentrifuge Isopropyl alcohol Aerobic organism Cell wall
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