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3/4/2017 DifferenceBetweenBacteriaandVirus|Classification,Structure,Metabolism
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DifferenceBetweenBacteriaandVirus
March2,2017 •byLakna •7min read
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MainDifference–Bacteriavs
Virus
Bacteria and viruses are microscopic microbes. Bacteria are
prokaryotes. They are living cells which can be either
beneficial or harmful to other organisms. But, viruses
consideredto be particles thatare somewhere between living
andnonlivingcells.Viruseshavetoinvadethebodyofahost
organisminorder to replicate theirparticles. Therefore, most
virusesarepathogenic.Themaindifferencebetween bacteria
and virus is that bacteria are living cells, reproducing
independentlyandvirusesarenonlivingparticles,requiringahostcellfortheirreplication.
Thisarticleexplains,
1.WhatareBacteria
–Classification,CellularStructure,Metabolism
2.WhatisaVirus
–Structure,Classification
3.WhatisthedifferencebetweenBacteriaandVirus
EXPLORE
Typeheretosearch...
3/4/2017 DifferenceBetweenBacteriaandVirus|Classification,Structure,Metabolism
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WhatareBacteria
BacteriaareprokaryotesfoundinmosthabitatsontheEarth.Theyareunicellularmicroorganisms.Bacteriacangrow
inharsh conditionslikeacidichot springs, radioactivewasteanddeep portionsofEarth’scrust.Bacteriaform dense
aggregationsbyattachingtosurfaces.Theseaggregationsarematlikestructurescalledbiofilms.
ClassificationofBacteria
Bacteriacanbecategorizeddependingontheirmorphology.Cocciarethesphericalshapedbacteria.Bacillusarethe
rodshapedbacteria. Commashaped bacteria are calledas vibrio andspiralshaped bacteria arespirilla and tightly
coiled ones are called as spirochaetes. Some bacteria live as single cells. But, some of them live in pairs and are
known as diploids. Streptococcus are the bacterial chains. Staphylococcus form ‘bunch of grapes’ like clusters.
FilamentsaretheelongatedbacterialikeActinobacteria.SomearebranchedfilamentssuchasNocardia.
Figure1:Cocci
CellularStructureofBacteria
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Bacterialcells are surroundedby a cell membrane. The membraneenclosed cytoplasm contains nutrients, proteins,
DNA and other essential components of the cell. Bacteria are prokaryotes and lack membranebound organelles.
Proteinlocalizationiscarriedoutbytheircytoskeleton.Asingle,circularchromosomeisfoundinthenucleoid.This
simplearrangementofbacteriaisreferredtoas‘bacterialhyperstructures’.
Mureinforms a cellwalloutsideofthe bacterialcellmembrane.Thethicker cell wallisclassifiedasgrampositive,
and the thinner cell wall is classified as gramnegative in the gram staining of bacteria. Flagella are used for the
mobility.Fimbriae are the attachment pili.Theyare used in the sexualreproductionofbacteria, which is knownas
conjugation.Theentirecelliscoveredbyglycocalyxwhichformsthecapsule.
Some genera of grampositive bacteria form a resistant, dormant structures called endospores. Endospores contain
littlecytoplasm,DNA and ribosomes, covered by acortex.Theyare resistant to radiation, detergents,disinfectants,
heat,freezing,pressureanddesiccation.
MetabolismofBacteria
Dependingon the carbon source, bacteriacan be divided into twogroups: heterotrophs and autotrophs.Thecarbon
sourceisorganiccompoundsinheterotrophswhereasthecarbonsourceiscarbondioxideinautotrophs.Dependingon
theenergysource,bacteriacanbedividedintothreegroups:phototrophs,lithotrophsororganotrophs.
WhatisaVirus
Avirusisaparticleconsideredasnonlivingform.Viruses
show neither respiration nor metabolism. A virus consists
ofits genetic material, eitherDNAor RNA, covered by a
protein core. Usually, viruses are infectious agents,
requiring a host for their replication. They infect all life
forms including animals, plants, bacteria and archaea.
Viruses can be found in almost every ecosystem on the
Earth. Thus, they are the most abundant biological entity
type. The study of virusesis called virology.Virusescan
bevisualizedbynegativestaining.
StructureofViruses
Thecompletevirusparticle is referred to as thevirion.Virionconsists of genetic materialenclosedbyaprotective
protein coat called as the capsid. The capsid is formed by identical protein units called capsomeres. The capsid
proteinsareencodedbytheviralgenome.Thevirionconsistsofacellmembranederivedfromthehostcellcalledthe
lipid envelope. Viral nucleic acid is associated with nucleoproteins. Viral capsid proteins and nucleoproteins are
collectivelycallednucleocapsid.
An enormous structural diversity in the genome is found in viruses when compared to the diversity of plants or
animals. A virus may contain either DNA or RNA genome. Hence, two groups of viruses can be identified: DNA
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virusesandRNAviruses.MostvirusescontainRNAgenomes.SinglestrandedRNAgenomescanbefoundinplant
viruses.DoublestrandedDNAgenomescanbefoundinbacteriophages.
ClassificationofViruses
TheICTV (InternationalCommitteeonTaxonomyof Viruses)classificationisthecurrentclassification systemused
forviruses.Thegeneraltaxonomystructureconsistsoforder,family,subfamily,genus,andthespecies.Caudovirales,
Herpesvirales, Ligamenvirales, Mononegavirales, Nidovirales, Picornavirales, and Tymovirales are the currently
established seven orders in viruses. Moreover, viruses are classified depending on the mechanism used to produce
their mRNA. This classification system is called Baltimore classification. According to this classification, seven
groups of viruses can be identified: dsDNA viruses, ssDNA viruses, dsRNA viruses, dsRNA viruses, (+)ss RNA
viruses,()ssRNAviruses,ssRNARTviruses,anddsDNARtviruses.
Onthecontrary,fourgroupsofvirusescanbeidentifieddependingon the morphology: helical, icosahedral, prolate
and envelope. The capsid forms a helical structure around the central axis in helical viruses. Icosahedral viruses
sometimesconsistofachiralicosahedralsymmetry.Inprolate,theicosahedroniselongatedintoafivefoldaxisasin
bacteriophages.Insomeviruses,thecellmembraneformsamodifiedformcalledtheenvelope.Thesetypeofviruses
arereferredtoasenvelopeviruses.Anicosahedralshaped,Simianvirusisshowninfigure2.
Figure2:SimianVirus
DifferenceBetweenBacteriaandVirus
DependenceontheHostforReproduction
Bacteria:Bacteriadonotneedahostorganismforreproduction.
Virus:Virusesreplicateonlyinsidethehost.
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LivingAttributes
Bacteria:Bacteriaarelivingorganisms.
Virus: Viruses are considered as organic structures which interact with living organisms, rather than a living
organism.
Size
Bacteria:Bacteriaarelarger,about1000nminsize.Theyarevisibleunderlightmicroscope.
Virus:Virusesaresmaller,about20400nminsize.Theyarevisibleundertheelectronmicroscope.
CellWall
Bacteria:BacteriacontainaPeptidoglycan/Lipopolysaccharidecellwall.
Virus:Virusesdon’thaveacellwall.Aproteincoatispresentinstead.
NumberofCells
Bacteria:Bacteriaareunicellular.
Virus:Virusesdon’thavecells.
GeneticMaterial
Bacteria:Asingle,circularchromosomeispresent.
Virus:DNA/RNAstrandispresent.
Ribosomes
Bacteria:Ribosomesarepresent.
Virus:Ribosomesareabsent.
Metabolism
Bacteria:Bacteriashowmetabolismwithinthecell.
Virus:Thereisnometabolisminsidetheviralparticle.
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Reproduction
Bacteria:Reproductionhappensthroughbinaryfissionandconjugation.
Virus: Virus invades the host cell, makes copies of genetic material and proteins, and releases new particles by
destroyingthecell.
CellularMachinery
Bacteria:Bacteriapossessacellularmachinery.
Virus:Viruslackcellularmachinery.
Benefits
Bacteria:Bacteriacanbeeitherbeneficialorharmful.
Virus:Virusesareusuallyharmful,canbeusefulingeneticengineering.
Infection
Bacteria:Bacteriacauselocalizedinfections.
Virus:Viruscausesystemicinfection.
DurationofIllness
Bacteria:Diseasescausedbybacterialastlongerthan10days.
Virus:Diseasescausedbyviruseslast2to10days.
Fever
Bacteria:Bacteriacausefever.
Virus:Virusesmayormaynotcausefever.
Treatments
Bacteria:BacterialinfectionscanbepreventedbyAntibiotics.
Virus:Spreadofvirusescanbepreventedbyvaccines.
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Examples
Bacteria:Staphylococcusaureus,Vibriocholera,etc.areexamplesofbacteria.
Virus:HIV,HepatitisAvirus,RhinoVirus,etc.areexamplesofviruses.
Diseases/Infections
Bacteria:Foodpoisoning,gastritis,ulcers,meningitis,pneumonia,etc.arecausedbybacteria.
Virus:AIDS,commoncold,influenza,chickenpox,etc.arecausedbyviruses.
Conclusion
Bacteriaandvirusesarebothmicroscopicmicrobes.Bothofthemcancausediseasesinplantsandanimals.Both
thesetypesofmicrobescontainenzymesrequiredfortheDNAreplicationandproteinsynthesis.But,virusesrequire
ahostorganismfortheproductionofviralcoatproteins.Therefore,theyshouldinvadeasecondorganismfortheir
replication.Ontheotherhand,bacteriacanreproduceindependentlybybinaryfission.Bothmicrobesconsistofa
hugediversitycomparedtootherlifeforms.Thekeydifferencebetweenbacteriaandvirusistheconsiderationof
eachformasalivingornonlivingorganism.
Reference:
1.“Bacteria”.Wikipedia,thefreeencyclopedia,2017.Accessed01March2017
2.“virus”.Wikipedia,thefreeencyclopedia,2017.Accessed01March2017
ImageCourtesy:
1.“108897”(PublicDomain)viaPixabay
2.“Symianvirus”ByPhoebus87atEnglishWikipedia(CCBYSA3.0)viaCommonsWikimedia
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AbouttheAuthor:Lakna
Lakna,agraduateinMolecularBiology&Biochemistry,isaMolecularBiologistandhasa
broadandkeeninterestinthediscoveryofnaturerelatedthings
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