In this article, You will read Difference between Virus and Bacteria – for UPSC IAS.

Virus and Bacteria

Bacteria are tiny microorganisms that are made up of a single cell. They’re very diverse and can have a large variety of shapes and structural features.

Bacteria can live in almost every conceivable environment, including in or on the human body.

Only a handful of bacteria cause infections in humans. These bacteria are referred to as pathogenic bacteria.

Viruses are another type of tiny microorganism, although they’re even smaller than bacteria. Like bacteria, they’re very diverse and have a variety of shapes and features.

Viruses are parasitic. That means they require living cells or tissue in which to grow.

Viruses can invade the cells of your body, using the components of your cells to grow and multiply. Some viruses even kill host cells as part of their life cycle.

difference between virus and bacteria


  • Viruses did not find a place in classification since they are not truly ‘living’, if we understand living as those organisms that have a cell structure.
  • The viruses are non-cellular organisms that are characterized by having an inert crystalline structure outside the living cell.
  • Viruses are obligate parasites. Once they infect a cell, they take over the machinery of the host cell to replicate themselves, killing the host.
  • The name virus that means venom or poisonous fluid was given by Pasteur.
  • In addition to proteins, viruses also contain genetic material, that could be either RNA or DNA.
  • No virus contains both RNA & DNA.
  • In general,
    • viruses that infect plants have single-stranded RNA &
    • viruses that infect animals have either single or double-stranded RNA or double-stranded DNA
    • bacteriophages (viruses that infect bacteria) are usually double-stranded DNA viruses.
  • The protein coat called capsid made of small subunits called capsomeres protects the nucleic acid.
  • These capsomeres are arranged in helical or polyhedral geometric forms.
Types of Viruses

Some examples of viral infections include:

  • influenza
  • common cold
  • viral gastroenteritis
  • chickenpox
  • measles
  • viral meningitis
  • warts
  • human immunodeficiency virus (HIV)
  • viral hepatitis
  • Zika virus
  • West Nile virus
  • COVID-19 is another illness caused by a virus. This virus commonly causes:
    • shortness of breath
    • fever
    • dry cough


  • Bacteria are single-cell, living organisms that can survive without a host.
  • They can live on surfaces, in soil, in water, & in the air.
  • You can kill them by messing with their ability to do cellular respiration or their ability to grow.
  • Antibiotics are used to treat bacterial infections because antibiotics kill bacteria.
  • Hence Antibiotics are useless against viruses.
  • There are some antiviral drugs that help protect you from a viral infection.
  • Antivirals either make it harder for the virus to get into the cell or they prevent the virus from reproducing once they are inside of your cells. 
  • Most bacteria reproduce by simply dividing into two.
  • Bacteria can cause diseases such as pneumonia & food poisoning.
  • However, not all bacteria are bad. In fact, some friendly types actually help protect us from the disease.

Some examples of bacterial infections include:

  • strep throat
  • urinary tract infection (UTI)
  • bacterial food poisoning
  • gonorrhea
  • tuberculosis
  • bacterial meningitis
  • cellulitis
  • Lyme disease
  • tetanus

Difference between Virus and Bacteria

They are very SmallThey are larger in size as compared to virus
Cell wall is absent but a capsid is present in them.Cell wall of bacteria is made up of lipopolysaccharide or peptidoglycan. 
Have no metabolism of their ownHave metabolism of their own
Take no food by any methodTake food by absorption
Do not grow & do not divideGrow in size & divide to produce more bacteria (by Cell-Division)
Command the host cell to produce a virus i.e. They cannot survive without a host.They can reproduce by their own i.e. They can survive without a host.
Can be crystallisedCannot be crystallised
They are only parasitic in nature.Bacterias are both pathogenic and parasitic in nature.
All produce diseases in man, animals & plantsSome are harmless, some useful & some are disease-causing
Contains only genetic material & protective coatingContains various cells subunits or organelles such as cytoplasm & cell wall which all perform specific functions
They have simpler DNA (if their genetic material is DNA)They have more complex DNA
Multiply faster than bacteriaMultiply slower than Viruses
Viruses are present in both living and nonliving formBacteria are totally living in nature
Vaccines prevent the spread & antiviral medicines help to slow reproduction but cannot stop it completelyThey can be treated with Antibiotics
Example– Common Cold, Flu & Sore ThroatExample– Strep Throat, Tuberculosis, Whooping Cough
difference between virus and bacteria UPSC


  • Viroids are infectious agents that are smaller than viruses.
  • A viroid is a free RNA, it lacks the protein coat that is found in viruses, hence the name viroid.
  • The RNA of the viroid was of low molecular weight.
  • Viroids cause potato spindle tuber disease.
It is a nucleoprotein particle.It is an RNA Particle.
Nucleic Acid can be DNA or RNA.Viroid is formed of only RNA.
A protein covering of coat is present.A protein coat is absent.
Virus has a larger size.Viroid has a smaller size.
Virus infects all types of organisms.Viroid infects only plants.

Difference Between DNA & RNA Viruses

  • A virus can self-replicate inside a host cell.
  • The infected cells may produce thousands of new copies of the original virus at an extraordinary rate.
  • The genetic material of a virus can be either DNA or RNA.
  • The viruses that contain DNA as their genetic material are called the DNA viruses.
  • RNA viruses, on the other hand, contain RNA as their genetic material.
  • DNA viruses are mostly double-stranded while RNA viruses are single-stranded.
  • RNA mutation rate is higher than the DNA mutation rate.
  • DNA replication takes place in the nucleus while RNA replication takes place in the cytoplasm.
  • DNA viruses are stable while RNA viruses are unstable.
  • Antigens: A substance which the body recognizes as alien & which induces an immune response.
  • Antibodies: A blood protein produced by the body in response to & counteracting an antigen.

Difference between DNA vs RNA

Deoxyribonucleic AcidRibonucleic Acid
Double-StrandedSingle Stranded
Deoxyribose SugarRibose Sugar
Self ReplicateCan’t Self-ReplicateIt is synthesized from DNA when required
Occurs inside the nucleus & of cell & some cell organelles (mitochondria) but in plants, it is present in mitochondria & plant cellIt is found in the cytoplasm of the cell but very little is found inside the nucleus.
DNA is the genetic material in all living organismsRNA is the genetic material in some viruses
Long Polymer ChainShorter Polymer Chain
Life of DNA is longerIts life is short
DNA occurs only in one form in any organism3 types of RNA are present in an organism: – mRNA, rRNA, tRNA
DNA is functional in the transmission of genetic informationIt forms as a media for long-term storageRNA is functional is the transmission of the genetic code that is necessary for the protein creation from the nucleus to the ribosome
Bases present are Adenine, Guanine, Cytosine, & ThymineBases present are Adenine, Guanine, Cytosine & Uracil

Difference between Gene & Genome

A gene is a part of DNA Molecule.The genome is total DNA in a cell.
The hereditary element of genetic information.All set of nuclear DNAs.
Encodes protein synthesis.Encodes both proteins & regulatory elements for protein synthesis.
Length is about a few hundreds of bases.Length of the genome of a higher organism is about billion base pairs.
A higher organism has about thousands of genes.Each organism has only one genome.
Variations of the gene named alleles can be naturally selected.Horizontal gene transfer & duplication cause large variations in the genome.

Which infections are treated with antibiotics?

Antibiotics are medications used to treat bacterial infections.

There are many types of antibiotics, but they all work to keep bacteria from effectively growing and dividing. They’re not effective against viral infections.

Despite the fact that you should only take antibiotics for a bacterial infection, antibiotics are often requested for viral infections. This is dangerous because over-prescribing antibiotics can lead to antibiotic resistance.

Antibiotic resistance occurs when bacteria adapt to be able to resist certain antibiotics. It can make many bacterial infections more difficult to treat.

If you’re prescribed antibiotics for a bacterial infection, take your entire course of antibiotics — even if you begin to feel better after a couple of days. Skipping doses can prevent killing all of the pathogenic bacteria.

Why antibiotics do not work on viruses?

Antibiotic target cellular structures and proteins present in the bacteria.

E.g. Antibiotics target bacterial cell walls, cellular enzymes, metabolic pathways, ribosomes, etc. Since viruses do not contain cellular structure, antibiotics do not affect them.

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Very nice material…..thanks sir