15 Differences between Bacteria and Virus

How is Bacteria different from Virus?

Bacteria are single celled prokaryotic microorganisms living in a variety of environments such as extreme cold and heat conditions or even within an organism.

Viruses are obligate intracellular parasites which require a living host for its survival. The debate on the status of virus as living or non-living is still open. Undoubtedly, viruses can be considered as sub-cellular particles that exhibit some properties of life.

Bacteria	Virus
Unicellular prokaryotes (without a true nucleus)	Sub cellular or acellular particles or without cellular organization
Visible under compound light microscope (~200-5000 nm in diameter)	Only visible under electron microscope (~20 to 400 nm in diameter)
Can live inside or outside host. Living in a variety of environments.	Strict intracellular infectious agents, always requires a living host.
Bacteria are living unicellular organism exhibiting properties of life such as cellular organization, metabolism, reproduction, homeostasis etc.	Viruses are considered as a border line between living and non-living things. It exhibits some properties of life such as presence of genetic material, ability to replicate inside the host, response to heat, chemicals etc. See more: Are viruses living or non-living?
Bacteria are living and cannot be crystallized.	Virus can be crystallized preserving their living properties.
Basic bacterial shapes are coccus (spherical), bacillus (rod-shaped), and spiral (twisted).	Viral shape: helical, cubical, binal or complex symmetry
A typical prokaryotic cell with DNA, cytoplasm, ribosome, plasmid, peptidoglycan cell wall and flagella	No cells. Only genetic material surrounded by a protein coat called capsid. In some viruses like HIV, an outer envelope is present outside capsid.
Genetic material is always DNA	Genetic material can be DNA or RNA, never both together
DNA is always double stranded	DNA or RNA can be single stranded or double stranded
Cellular machinery for DNA replication and protein synthesis.	No cellular machinery. Replication of genetic material and protein synthesis using machinery of the host
Reproduce by itself by binary fission, an asexual reproduction method	Inject genetic material into the host and replicates inside the host using hosts cellular machinery; either causing breakage of cell releasing intact infectious virions (lytic cycle) or attaching to the host genome as prophage and replicate along with host genome replication (lysogenic cycle) More details: lytic vs lysogenic cycle
The majority of bacteria ~90% are harmless, or beneficial, or even essential to life. Only less than 10% are harmful and disease causing.	Viruses are harmful infectious agents. But genetically engineered viruses are widely used in rDNA technology and gene therapy as vectors. Lentivirus in gene therapy and phage vectors like cosmid in rDNA technology
Bacteria often cause localized infection (in one part of the body or confined to an organ) and often associated with fever. Eg: Skin infection(eczema),wound infection	Virus often cause systemic infection (spreads throughout the body) and may or may not induce fever. Eg: AIDS
Bacterial infection is treated with antibiotics Eg: Penicillin, Amoxicillin etc	Antibiotics cannot kill viruses. Vaccines are widely used to prevent viral infection. Eg: Varicella (chickenpox) vaccine, Measles, Mumps and Rubella (MMR) vaccine
Common Bacterial diseases: Food poisoning: Escherichia coli  Tuberculosis-Mycobacterium tuberculosis	Common Viral diseases: Common cold: Corona virus, Rhino virus etc Chickenpox caused by Varicella zoster virus