Virology: Virus Structure and Morphology

MSC-MICROBIOLOGY-I PONDURI MANASA VIRUS STRUCTURE AND MORPHOLOGY ~ introduction charecteristic features. -> Size. → structure & Morphology" → Importence Function. Introduction viruses are which acellular obligate intracellular parasites mean Venom/poisionous fluid. AS they are acellular & do not have a propel shape, they aure not kept in any kingdom.of classification. because they are not truely living. →→→They are smallest known Infective agents & perhaps the simplest form of life & can be viewed With Electron microscope →For the first time the virus was observed in tobacco plants by Ivanowsky Passed through bacteria proof te where they filters Later beijerinck demostrated that extract of infected plant of tobacco could infection in "as "Contagium cause healthy plants & is called fluid Vivum Hui odom →stanley had crystallised TMV for first time. → The Ustudy of viruses charecteristics features is known as Virology → obligate parasites & absence of respiration, growth & division They have no internal cellular structure →contain Either DNA or RNA →They are but not both incapable of metabolism. →They Replicate only inside the living (host) cells. →They can be easily crystallised. →They composed of dudeic acids → wrapped in Protein coatlapsd)so called nucleoproteins. They Can undergo mutations → Genetic material can be linear or circubo may hare Positive / Negative polarity Some has structural Internal & core proteins E Some viral enzymes. Size. They are 10 to 100 times smaller than bacteria & size ranges from 20 to 300 nm So they Can easily pars through bacterial filters. Structure of virus & Morphology →it consists of three structural components They are (i) Nucleic acid (99) protein (capsid) () Envelope. (some) Nucleic acid - it contain acid either a single type of nudeic DNA or RNA as genetic material *DNA Containing called deoxyviruses of 2 types (i) dsDNA Eg:-Poxvirus, Herpes, cauliflowermosaic () SSDNA Eg: Coliphage x174, M13 phage *RNA Containing called riboviruses of a types (9) SS RNA Eg:- TMV, Influenza, Retrovirus. (DS RNA Eg:- Reovirus, wound tumour virus. Protein (capsid):- protective shell around nudeic acid consists of subunits called capsomers Envelope - Some virus families have an additional Covering called A envelope * Virus Virus containing envelop are called enveloped * virus containing without envelop are called naked virus → on the outersurface of envelope glycoprotein Subunits Spikes are known exposed in form of projecting as peplomere. Capsormers copsid peplomers. FO envelge FO FO →Nucleic acid. fos capsid capsomers Enveloped viazis Nodcicard Naked vines. Depend on Capsid structure it is classified into different types. (i) Helical (%) Polyhedral (sosahedral) (i) Enveloped (iv) Complex. (9) Helical Symmentry be rigid & flexible →Resemble long rods that may be rigid →2130 Capsomers form Capsid- are arranged helically which & hallylindrical to →Genetic onaterial is single stranded RNA bound into protein helix by interadion blw negatively Charged nudeicacid & positively charged protein →it consists of byoo nucleotides. →Ratio of nucleotides: Capsomeres = 3:1 (ii) polyhedral (Icosahedral) →Many bacterial, plant & animal virus are polyhedral capsid is in shape of Icosahedron (ie have 10 faces or sides & 12 corners) together Nucleic acids, with certain proteins, is highly packed in a central around core, forming a pool of parallel loops a cylindrical hole. Ex'r Adenovirus, poliovirus. (i) Enveloped virus Roughly spherical but highly pleomorphic (varicable in shape) →when helical / polyhedral viruses Envelope are are endosed by an called enveloped helical (Influenza Virus) & envelop polyhedral (Herpes simplex virus) →viral envelop is responsible for protection of virus from enzymes & Contain chemicals most enveloped viruses are dependent on envelo for infectivity. Nucleic acid -Capemer envelop spiter Helical Polyhedral (iv) Complex virus Some virus particularly bacterial viruses have very complicated structures there are complex viruses →virus that infect bacteria is called bacteriophage it infect E.coli are called Teven phage (Tyіть) →There phages have complex & charecteristic morph -ology. →They are tadpole shape with hexagonal head & cylindri - cal tail →Head consists of tightly Packed core of nucleic acid (DNA) Surrounded by capsid →The size of head varies in different phages from 28 nm to 100 nm. Tail is composed of hallow core, a contractive sheath surrounding core & terminal base plate which has attached to it prongs, tail fibre or both. The base Six tad fibres of the tail has six ping & are attached that bind to Specific receptor sitee bacterial surface Importence →Viruses are used to study of molecular & cell biology that as to provide simple systems. can be used Investigate to manipulate ६ fonctions of cells. They are used in genetics to understand DNA Replication, transcription, translation, RNA Processing, protein transports etc → Virus also genes into used cells which helps to as vectors to introduce they are studying treat various diseases.. Function:- The primary role of virus is to dedives DNA/RNA genome into host cell so that genome Can be Can expressed by host cell which replicate inside the host cells. Detection of viruses growth in cell culture Indirect Detection' →Enhanced virus isolation →Direct detection →Nucleic acid based Detection methods. → Real Time quantitative polymerase chain Reaction" → Cytopathic Ellects →metabolic inhibition * Inclusion bodies * chromosomal abberations: *Cell Transformation * cell fusion →oncogenic viruses → Cytopatho goure Viruses →Diagram →Absorbance Indirect detection. Indirect detection methods involve the propagation of virius particles via their introduction to a Suitable host cell line. This is termed Vines isolation →Sometimas, taking weeks for the virus to pro pagate, moderu -ised methods have allowed the turn around to be greatly improved (leland and ginocchio, 2007) Enhanced Vivus isolation methods. →Centrifuge - Enhanced shell-Vial techiques or well plates termed chestos plates, faciliatale Rapid Adsorption of the Virus into the hast cell line by applying love, level Centrifuge, greatly Reducing for inoculation of cell line the length of time Required Direct Detection Direct detection methods negate the need for the Virus Propogation - the Virus is delected directly from the Suspect Sousen il is usually involves * Sophisticated Techniques * Nucleic acid * immunological detection Abe Reaction →This is facilidated by Drin intercalating dyes; Such as SYBR green, of flouiscently labelled probes all double Stranded 'DNA →DNA dyes will brud to To we this dyes, the primers must be highly optimisés and produce no non-specific Amplicant → probes include those which must bind to a specific region on targel DNA... Eq. hydrolysis a hybrdization probes Cytopathic Effects → It mainly consists of Causation of morphological changes in the host Cells → Sometimes these alternations may ever lead to Celi death for Eg: we may Site the and cynophages on lytic Effects of bacteriophages the host bacterial Cyanophycean cells Respectively and the a) Adenovirus infected cells Round up and aggregate in clusters before their Evenful death. b) cells affectical by poliovirus Round Eventually getting totally destroyed up and shrink → the Effects of Some plant viruses in their hast cells a) In hus's infected by plant viruses (pe, leads to pasital tabel chlorosis of chlorphyllous parts. 5 unequal growth of Cell wall leading to all stock of curvative of different organs... c) Shrinkage and clustering of cells which leads to Celle death Viruses having lipid membranes like myxovirus infection leads to disintergation of host Cell membrane inte fragmeids → in Cells infrated with herpesvirus the infecting membranes by contigous celle dissolved Recalling into the formation of giant Cells Metabolic inhibition →In bacteriophage, Cyanopliage and Some mammalian Vivus infected cells, depression and essential metabolic the host cell protein Synthesis in shed down at instance of vival proteins which may be pad of the infective Vivion →Cellular Dron cand Ron Synthesis. are affected only Secondarily. The Shut down is found to be Particularly Rapid in cultured cells infected by picoruvivuses el herpes viruses Inclusion bodies large no. of hast virion Systems - develop as a consequence to the of Virions at B aggregation particular site in the cell at time of their formation →pin wheel like inclusion bodies of poly Virus infection auc another Example Eg:- Adenovirus infection & mammalian hösts Chromosomal Abbewadions celle in culture when infuted by a variety of Viruses show chromosomal abhewalion like breaks and Constrichon The breates, induced by herpes af centrin sites of Virus olhe 2 Specific chromesmes only → the progeny of host Celly fach abbewation Continuel to show Cell Transformation → Some viral infection leads to alteration in maghéj sof infected Cells →Transformation cau be recognized by a) presence of intercellular 7. antigens by contact inhibition I ability to Cause tumors when inoculated into Suitable hast Cell fusion: Some Vivuter herpes viruses & lilec paramyxovirus Por viruses produce giant cells