What are the differences between bacteria and viruses?

Basis of differentiation 

Bacteria 

Viruses 

Definition 

Are free-living cells that can live inside or outside a body

Are non-living collection of molecules that need a host to survive

Number of cells

One cell (unicellular)

No cells (acellular) 

Size 

Large, 900 - 1000 nm

Smaller 30-500 nm

Visibility 

Visible under Light Microscope

Visible only under Electron Microscope

Cell wall

Has a cell wall composed of Peptidoglycan or Lipopolysaccharide

Does not have a cell wall, instead the genetic material is enveloped by a protein coat known as a capsid

Cellular machinery 

Possesses a cellular machinery

Lack cellular machinery

Characteristics of DNA and RNA

DNA and RNA float freely in cytoplasm

DNA or RNA are enclosed inside a coat of protein known as capsid

Ribosomes 

Present 

Absent 

nucleus

no

no

Ability to reproduce 

Able to reproduce by itself

Need a living cell to reproduce

Mode of reproduction 

Asexually by binary fission, which is a form of asexual reproduction

Invade a cell host and insert their genome in the host genome, making multiple copies of the viral DNA/RNA, thus destroying the host cell and releasing new viruses

Mode & Type of infection

Opportunistic and localized infection – Bacteria typically infect the host when the opportunity arises and the infection is confined to one part of the body

Systemic infection – After infecting a host cell viruses multiply by the thousands, leaving the host cell and spreading the infection throughout the body 

Common diseases caused

Tetanus, food poisoning, gastritis and ulcers, meningitis, pneumonia, and tuberculosis 

Influenza, AIDS, common cold, measles, chickenpox, polio and COVID-19

Duration of illness

Longer than 10 days

About 2 to 10 days

Treatment 

Antibiotics are an effective treatment

Do not respond to antibiotics. Antiviral drugs and vaccines prevent the spread of viruses and slow reproduction

Virulence

yes

yes

Fever 

Bacterial infection typically causes a fever

Viral infection may or may not cause a fever

Examples 

Staphylococcus aureus, Vibrio cholerae, 

HIV, Hepatitis A virus, RhinoVirus,