classification of virus :LHT,HOLMES,BALTIMORE,ICTV
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This document discusses several methods for classifying viruses: 1. The Holmes classification from 1948 grouped viruses into 3 categories based on their host organisms. 2. The LHT classification from 1962 categorized viruses based on their physical and chemical properties like nucleic acid composition and capsid structure. It divided viruses into DNA and RNA subgroups. 3. The Baltimore classification from 1971 organized viruses into 7 groups according to their nucleic acid type and replication strategy. 4. The current ICTV classification recognizes 9 orders that group viruses based on genetic and biological properties. It aims to reflect modern understanding of virus relationships and diversity.
classification of virus :LHT,HOLMES,BALTIMORE,ICTV
- 1. CLASSIFICATION OF VIRUS : LHT, HOLMES, BALTIMORE AND ICTV CLASSIFICAION Sivasangari shanmugam
- 2. VIRUS Small infectious agent. Replicate only inside the living cells. Meaning Venome (or) Poisonous fluid. Made up of nucleic acid and proteins. TMV is a first virus discovered by Ivanowski in 1892.
- 3. VIRUS CLASSIFICATION Virus mainly classified, based on heir following character. 1. Phenotype character. 2. Mode of replication. 3. Host organisms. 4. Types of disease they cause.
- 4. VIRUS CLASSIFICATION Virus has four classification. 1. Holmes classification. 2. LHT classification. 3. Baltimore classification. 4. ICTV classification.
- 5. VIRUS CLASSIFICATION Holmes classification Holmes (1948) used Carl linaeus's system of binomial nomenclature. To classify viruses into 3 groups under one order, virales, They are, Group I: Phaginae (attacks bacteria) Group II: Phytophaginae (attacks plants) Group III: Zoophaginae (attacks animals)
- 6. VIRUS CLASSIFICATION LHT classification It is based on chemical and physical characters like nucleic acid (DNA or RNA), Symmetry (Helical or Icosahedral or Complex), presence of envelope, diameter of capsid, number of capsomers. This classification was approved by the Provisional Committee on Nomenclature of Virus (PNVC) of the International Association of Microbiological Societies in 1962.
- 7. LHT CLASSIFICATION It is as follows: Phylum Vira (divided into 2 subphyla) 1. Subphylum Deoxyvira (DNA viruses) 1.1.Class Deoxybinala (dual symmetry) Order Urovirales Family Phagoviridae 1.2.Class Deoxyhelica (Helical symmetry) Order Chitovirales Family Poxviridae
- 8. LHT CLASSIFICATION 1.3.Class Deoxycubica (cubical symmetry) Order Peplovirales (mantle viruses) Family Herpesviridae (162 capsomeres) Order Haplovirales (no envelope) Family Iridoviridae (812 capsomeres) Family Adenoviridae (252 capsomeres) Family Papiloviridae (72 capsomeres) Family Parvoviridae (32 capsomeres) Family Microviridae (12 capsomeres)
- 9. LHT CLASSIFICATION 2. Subphylum Ribovira (RNA viruses) 2.1.Class Ribocubica (cubical symmetry) Order Togovirales Family Arboviridae Order Lymovirales Family Napoviridae Family Reoviridae 2.2.Class Ribohelica (helical symmetry) Order Sagovirales Family Stomataviridae Family Paramyxoviridae Family Myxoviridae
- 10. LHT CLASSIFICATION Order Rhabdovirales Suborder Flexiviridales (Plant viruses) Family Mesoviridae Family Peptoviridae Suborder Rigidovirales (Plant viruses) Family Pachyviridae (20 nm) Family Protoviridae (15 nm) Family Dolichoviridae (12-13 nm)
- 11. VIRUS CLASSIFICATION Baltimore classification Classified by David Baltimore in 1971. Classified seven groups based on, Nucleic acid (DNA/RNA). Strand (double/single). Sense (positive/negative). Methods of replication.
- 12. VIRUS CLASSIFICATION Baltimore classification Seven groups are given below : 1. Double stranded DNA 2. Single stranded positive (+) sense DNA 3. Double stranded RNA 4. Single stranded positive (+) sense RNA 5. Single stranded negative (-) sense RNA 6. Single stranded positive (+) sense RNA with DNA intermediated 7. Double stranded DNA with RNA intermediate
- 13. BALTIMORE CLASSIFICATION Double stranded DNA Include viruses are, Adenoviruses,Herpesviruses, Poxviruses, etc.. Replicate in nucleus – Ex: Adenoviruses. Replicate in cytoplasm – Ex: Poxviruses. SS (+) sense DNA Involving the formation of a (-)sense strand. Replication occurs in nucleus. Ex: Parvovirus. Double stranded RNA Have segmented genome. Each genome is transcribed separately produce monocistronic mRNA. Ex: Reoviruse , Pirnavirus. SS (+) sense RNA Polycistronic mRNA - Ex: Picrnovirus , Hepatitis A. Complex transcription – Ex : togaviruses
- 14. BALTIMORE CLASSIFICATION SS (-) sense RNA Segmented - Ex : Orhomxoviruses. Non segmented – Ex : Rhabdoviruses. SS (+) sense RNA with DNA intermediate Does not serves as mRNA. template for reverse transcription . Ex : Retroviruses DS RNA with DNA intermediate Ex : Hepadnaviruses.
- 16. ICTV CLASSIFICAION ICTV – International committee on taxonomy nomenclature virus. It includes, Orders – 09 Families – 131 Sub families – 46 Genera – 803 Species – 4,853
- 17. ICTV CLASSIFICATION The 9 orders are, 1. Herpsvirales – Large eukaryotic ds DNA viruses. 2. Caudovirales – Tailed ds DNA bacteriophage. 3. Ligamenvirales – Linear ds DNA archean virus. 4. Mononigavirales –Monosegmented (-) strand ssRNA plants & animals viruses. 5. Nidovirales – (+) strand ssRNA viruses with vertebrates hosts. 6. Ortervirales – ssRNA & DNA that replicate through a DNA intermediate. 7. Picornovirales – Small (+) strand ssRNA viruses. Infect variety of plants & animals. 8. Tymovirales – Monopartite (+) sense viruses that infects plants. 9. Bunyavirales – Tripartite (+) sense ssRNA viruses.
- 18. REFERENCE 1. https://www.ncbi.nlm.nih.gov/books/NBK8174/ 2. https://viralzone.expasy.org/254 3. https://microbeonline.com/baltimore-system- classifications-viruses/ 4. https://bio.libretexts.org/Bookshelves/Microbiology /Book%3A_Microbiology_(Boundless)/9%3A_Viru ses/9.3%3A_Classifying_Viruses/9.3B%3A_The_ Baltimore_Virus_Classification 5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC36 89849/
- 19. THANK YOU !