Classification of plant virus, animal virus and phages examples

1. CLASSIFICATION OF VIRUSES -
ANIMAL VIRUSES, PLANT
VIRUSES AND PHAGES

2.  Viruses are described as simple, acellular, infectious agents that can parasitise
all forms of life.
 They are simply the packages of a genetic information inside a protein coat.
 It is a biological agent that exhibits pseudo living.
 They are obligate intracellular parasites.
 They cannot be cultured in the laboratory.
 They contain a single type of nucleic acid - DNA or RNA.
 They can be viewed only under the electron microscope.
 They are potentially infectious - can attack different hosts.

3.  The complete fully developed
infectious viral particle is
known as the virion.
 The virion consists of the
nucleic acids core called as
genome which is surrounded
by a protein coat called as
capsid.
 The capsid together with the
nucleic acid is called as nucleo
capsid.
 Some viruses are covered with
an other protective covering
called as the envelope.

4. Basis for the classification of viruses:
 Virion morphology
 Physiochemical properties of the virion.
 Virus genome properties
 Virus protein properties
 Genome organisation and site of replication
 Specific surface structures
 Natural host range, pathogenicity and pathology.
 Mode of transmission and vector relationships.

5.  In principle, each of the above characters can be used for the classification of
viruses.
 But the chemical nature of the nucleic acid plays the most important role in
classifying the viruses.
 1971 - David Baltimore proposed a classification that was based on the nature
of the virus genome and their mode of replication and their gene expression.
 According to the Baltimore classification system of virus, all viruses are
divided into seven classes on the basis of their mechanism of mRNA
synthesis, replication stratergy and whether the genome is single or double
stranded nucleic acid.
 This scheme takes no account of their biological properties and groups very
different virions together in the same class.
 For example, bacteriophages and animal viruses are together in class 1,
although they are totally different in structure and biology.

6.  The ICTV uses Baltimore scheme along with the other parameters,
to palce viruses into families and genera.
 By 1995, the ICTV has organised more than 4,000 animal viruses
into 71 families, 11 subfamilies and 175 genera.
Viruses are mainly grouped into three major categories. They are:
1. Animal viruses - Zoophaginae
2. Plant viruses - Phytophaginae
3. Bacterial viruses - Phaginae
Currently two main classification systems have been used. They are:
 Baltimore classification system
 ICTV classifiation system

7.  It is a classification system based on the combination of their nucleic
acid (DNA or RNA), strandedness (single-stranded or double-
stranded), Sense, and method of replication.
 It places the viruses into 7 groups. They are:
I: dsDNA viruses (e.g. Adenoviruses, Herpesviruses, Poxviruses)
II: ssDNA viruses (+ strand or "sense") DNA (e.g. Parvoviruses)
III: dsRNA viruses (e.g. Reoviruses)
IV: (+)ssRNA viruses (+ strand or sense) RNA (e.g. Picornaviruses, Togaviruses)
V: (−)ssRNA viruses (− strand or antisense) RNA (e.g. Orthomyxoviruses,
Rhabdoviruses)
VI: ssRNA-RT viruses (+ strand or sense) RNA with DNA intermediate in life-
cycle (e.g. Retroviruses)
VII: dsDNA-RT viruses (e.g. Hepadnaviruses)

8.  The International Committee on Taxonomy of Viruses began to devise and
implement rules for the naming and classification of viruses
 Viral classification starts at the level of order and continues as follows, with
the taxon suffixes given in italics:
ORDER (virales)
FAMILY (viridae)
SUB FAMILY (virinae)
GENUS (virus)
SPECIES
 As of 2012, seven orders, 96 families, 22 subfamilies, 420 genera, and 2,618
species of viruses have been defined by the ICTV.
 Caudovirales
 Herpesvirales
 Ligamenvirales
 Mononegavirales
 Nidovirales
 Picornavirales
 Tymovirales

9. ANIMAL VIRUSES & ITS
CLASSIFICATION

10. Animal viruses:
 Viruses that infect the animals are known as animal viruses.
 They are included in the group Zoophaginae.
 Animal viruses contain DNA.
 Some animal viruses contain RNA.
 The nucleic acids may be single stranded or double stranded.
 The animal viruses cause dangerous diseases in human beings and domestic
animals.
 The common animal viruses are : Poliovirus, Vaccinia virus, Adenovirus,
Herpes virus, Reo virus, Dengue virus, Yellow fever virus, Rabies virus, Mumps
virus, Measles virus, Influenza virus, HIV.
 Animal viruses are presently grouped into 32 families.

11. Family Envelope and genome Examples
Adenoviridae Non enveloped; double
standed DNA of 25,000-
42,000 base pairs.
Human adenovirus type 1
and 5, Fowl adenovirus
type 1.
Ascoviridae Enveopled; double
stranded DNA of 10,000
to 1,80,000 bp.
Ascovirus
Asfarviridae Enveloped; double
stranded DNA of 1,70,000
to 1,90,000 bp.
African swine fever virus
Baculoviridae Enveloped; double
stranded DNA of 80,000
to 1,80,000 bp.
Baculovirus
Herpesviridae Enveopled; dsDNA of
1,20,000 to 2,40,000 bp.
Human herpes virus type
1 and 2, Varicella Zoster

12. Family Envelope and genome Examples
Papillomaviridae Non enveopled, dsDNA of
8000 bp molecule.
Human paillomavirus
(HPV)
Polydnaviridae Enveopled; dsDNA upto
3,00,000 bp.
Ichnovirus, Polydnavirus
Poxviridae Enveopled; dsDNA of
1,30,000 to 3,75,000 base
pairs.
Vaccinia, Cowpox,
fowlpox, smallpox, sheep
pox, entomopox virus.
Polyomaviridae Non-enveopled; dsDNA
of one 5,000 base pair
molecule.
Murine polyomavirus and
SV 40.

13. Family Envelope and genome Examples
Circoviridae Non-enveopled; one
molecules of ssDNA.
Chicken anemia virus
Parvoviridae Non-enveopled; positive
or negative sense ssDNA
Parvovirus,
Erythrovirus(B 19 virus)

14. Family Envelope and genome Examples
Birnaviridae Non-enveloped; two
segments of linear dsRNA
of 2,800 and 3,200
nucleotides.
Pancreatic necrosis virus
of fish
Reoviridae Non-enveopled; dsRNA
of 18,000 to 30,000 base
pairs.
Rotavirus, Orbivirus,
Cypovirus

15. Family Envelope and genome Examples
Arteriviridae Enveloped virus; Positive
sense ssRNA
Arterivirus
Astroviridae Non-enveopled; Positive
sense ssRNA
Human,bovine and duck
astroviruses
Caliciviridae Non-enveloped; positive
sense ssRNA
Human calicivirus,
Hepatitis E virus, Norwalk
virus
Coronaviridae Enveloped; positive sense
ssRNA.
Avian bronchitis virus and
huan coronavirus - OC43.
Flaviviridae Enveopled; positive sense
ssRNA
Flavivirus, Pestivirus
Nodaviridae Non-enveloped; Positive
sense ssRNA
Alphanodavirus and
Betanovirus
Picornaviridae Non-enveloped; positive Enterovirus, Hepatovirus

16. Family Envelope and genome Examples
Arenaviridae Enveloped; Negative
sense ssRNA
Arenavirus
Bornaviridae Enveloped; Negative
sense ssRNA
Borna disease virus
Bunyaviridae Enveloped; negative
sense ssRNA
Bunyamvirus
Filoviridae Enveloped; negative
sense ssRNA
Marburg, Ebola and
Reston virus
Orthomyxoviridae Enveloped; negative
sense ssRNA
Influenza virus (A,B and
C)
Paramyxoviridae Enveloped; negative
sense ssRNA
Respirovirus, Rubulavirus

17. Family Envelope and genome Examples
Retroviridae Enveloped; Positive sense
ssRNA of 7,000-11,000
nucleotides.
Mammalian type C
retrovirus,
Alpharetrovirus,
Lentivirus
Family Envelope and genome Examples
Hepadnaviridae Enveloped; negative
sense dsDNA. These are
“Reversiviruses” that
have a reverse
transcriptase.
Orthohepadnavirus,
Avihepadnavirus

19. Plant Virus:
 Viruses that infect plant cells are called as plant viruses.
 About 170 plant viruses have been identified.
 Most of the plant viruses contain RNA as the genetic material.
 But only one group of virus contains DNA as the genetic material.
 The RNA may ne single stranded or double stranded.
The following are the important plant viruses:
 Tobacco mosaic virus (TMV)
 Tomato mosaic virus
 Potato virus
 Papaya mosaic virus
 Cucumo virus
 Tobacco necrosis virus
 Alfalfa mosaic virus
 Cauliflower mosaic virus

20. Family Circoviridae:
Non-enveloped virus.
The family contains two genera, one infects the animals and the other
infects the plants.
 Genus Nanovirus - Type species : Subterrnean clover stunt virus.
Family Geminiviridae:
Non-enveloped virus
The family contains 4 genera.
 Genus Mastrevirus - Type species: Maize streak virus
 Genus Curtovirus - Type species: Beet curly top virus
 Genus Begomovirus- Type species: Bean golden mosaic virus
 Genus Topocuvirus- Type species: Tomato pseudo curly top virus

21. Family Partitiviridae:
Non-enveloped virus
Two genera of this family infect fungi and two infect plants.
The plant-infecting genera of this family are known as “Cryptic virus” as they
cause very few or no symptom.
Genus Alphacryptovirus - Type species: White clover cryptic virus 1
Genus Betacrypticvirus - Type species: White clover cryptic virus 2
Family Reoviridae:
Non-enveloped virus
This family has three genera which infects the plants.
Genus Fijivirus - Type species: Fiji disease virus
Genus Oryzavirus - Type species: Rice ragged stunt virus
Genus Phytoreovirus- Type species: Wound tumour virus
Genus Varicosavirus- Type species: Lettuce big vein virus

22. Family Comoviridae:
Non-enveloped.
This family contains 3 genera.
Genus comovirus – Type species: Cowpea mosaic virus
Genus fabavirus – Type species: Broad bean wilt virus 1
Genus Nepovirus – Type species: Tobacco ring pot virus
Family Luteoviridae:
Non-enveloped
This family contains 3 genera.
Genus Luteovirus – Type species: Barley yellow dwarf virus
Genus polerovirus – Type species: Potato leaf roll virus
Genus Enamovirus – Type species: Pea enation mosaic virus
Family Sequiviridae:
Non-enveloped
This family contains 2 genera
Genus Sequivirus – Type species: Parsnip yellow fleck virus
Genus Waikavirus – Type species: Rice tungro spherical virus

23. Family Tombusviridae:
Non-enveloped
This family contains only 9 genus.
Genus Tombusvirus – Type species: Tomato bushy stunt virus
Genus Aureusvirus – Type species: Pothos latent virus
Genus Avenavirus – Type species: Oat chlorotic stunt virus
Genus carmovirus – Type species: Camation mottle virus
Genus Machlmovirus – Type species: Maize chlorotic mottle virus
Genus Necrovirus – Type species: Tobacco necrosis virus A
Genus Panicovirus – Type species: Panicum mosaic virus
Genus Dianthovirus – Type species: Carnation ring spot virus
Family Bromoviridae:
Non- enveloped
This family contains 5 genus
Genus Bromovirus- Type species: Brome mosaic virus
Genus Cucumovirus – Type species: Cucumber mosaic virus
Genus Alfamovirus – Type species: Alfalfa mosaic virus
Genus Ilarvirus – Type species: Tobacco streak virus
Genus Oleavirus – Type species: Olive latent virus 2.

24. Family Closteroviridae:
Non-enveloped.
This family contain two genera.
Genus Closterovirus – Type species: Beet yellow virus
Genus Crinivirus – Type species: Lettuce infectious yellow virus
Family Potyviridae:
Non-enveloped.
This family contains
Genus Potyvirus – Type species: Potato virus Y.
Genus Ipomavirus – Type species: Sweet potato mild mottle virus
Genus Macluravirus – Type species: Maclura mosaic virus
Genus Rymovirus – Type species: Ryegrass mosaic virus
Genus Tritimovirus – Type species: Wheat streak mosaic virus
Genus Bymovirus – Type species: Barley yellow mosaic virus

25. Family Bunyaviridae:
Enveloped.
This family contains 3 genera.
Genus Tospovirus- Type species: Tomato spotted wilt virus
Genus Ophiovirus – Type species: Citrus psorosis virus
Genus Tenuvirus – Type species: Rice stripe virus
Family Caulimoviridae:
Non-enveloped.
This family contains 3 genera
Genus Caulimovirus - Type Species: Cauliflower mosaic virus
Genus Badnavirus - Type species: Commelina yellow mottle virus

26. PHAGE & ITS
CLASSIFICATION

27. Bacteriophages:
 Viruses that infect the bacterial cells are called as bacterial viruses or
bacteriophages.
 Bacteriophage means viruses eating bacteria.
 They were first described by Twort in 1915.
 The genetic material is either DNA or RNA.
 They may be single stranded or double stranded.
 The common bacteriphage is T4 bacteriophage.
 It infects the human colon bacterium, Escherichia coli.
 “T” stands for the “type”.
 Bacteriophages are numbered from 1 to 7.

29. Family Siphoviridae:
 Infect a number of bacteria like Enterobacteria, Mycobacteria, Lactococcus,
Methanobacterium and Vibrio.
 Include phages like T1, Lambda and phi 80.
Family Myoviridae:
 Infects bacteria like Enterobacteria, Bacillus and Halobacteria.
 This family includes the “T-even” coliphgaes T2, T4 and T6 and PBS1,
P1,P2,P3,P4.
Family Podoviridae:
 Infects bacteria like Enterobacteria and Mycobacteria.
 This family includes - T3, T7 coliphages, Enterobacteria phage P22, Bacillus
phage phi 29.
Family Fuselloviridae:
 Infects archaebacteria.
 Eg: Sulfolobus virus 1.

30. Family Tectiviridae:
 Mostly infects gram-negative bacteria.
 Examples: Enterobacteria phage PRD 1.
Family Corticoviridae:
 Mostly infects pseudomonas.
 Example: Alteromonas phage PM2.
Family Plasmaviridae:
 Mostly infects mycoplasma
 Examples: Acholeplasma phage L2.
Family Rudiviridae:
 Mostly infects thermophilic archaeobacteria.
 Example: Sulfolobus virus SIRV-1.
Family Lipothrixviridae:
 Mostly infects thermophilic archaeobacteria.
 Example: Thermoproteus virus 1.

31. Family Inoviridae:
 Virions long, rod shaped or filamentous, non-enveloped with the
helical symmetry. This family includes 2 genera:
Genus Inovirus - Enterobacteria phage M13 and Enterobacteria phage fd.
Genus Pleactovirus - Acholeplasma phage MV-L51.
Family Microviridae:
 This family includes 4 genera. They are as follows:
Genus Microvirus - Enterobacteria phage phi 174.
Genus Spiromicrovirus - Spiroplasma phage 4.
Genus Chlamydiamicrovirus - Chlamydia phage 1.
Genus Bdellomicrovirus - Bdellovibrio phage MAC 1.

32. Family Cystoviridae:
 Virions are enveloped.
 Infects pseudomonas.
Example: Pseudomonas phage phi 6.
Family Leviviridae:
 Members of this family are enveloped with icosahdral symmetry.
 Includes Enterobacteria phages R17, MS2 and Qβ.