Difference between Bacteria and Virus

Key Difference: Bacteria are single celled and prokaryotic organisms. They replicate in an asexual manner. They can be harmful as well as beneficial; it depends upon the type of bacteria. On the other hand, Viruses are non living pathogens and are acellular. A Virus also needs a host cell in order to reproduce. Most of the Viruses do not serve any useful purpose.

Bacteria are single cell plant organisms and they are very small in size, measuring about a few microns in size (micron=0.001mm). Bacteria are different from other cellular forms as they do not have any nucleus. Many of the Bacteria also inhabit our skin, mouth and intestine. They help in digestion and also keep the number of bad bugs under control.

On the other hand, Virus is a mobile genetic material that is enclosed in a protein or a fatty shell. They are smaller than bacteria, ranging between (0.1 to 0.3 microns) in size. They were discovered just before 1900, and were known as filterable Viruses due to their small size. A debatable issue is regarding their status as living or non living. This is due to the fact that they consist of merely nucleic acid that is wrapped in a coat of protein.

The characteristics are listed below:-

	Bacteria	Virus
Structure	Most bacteria consist of a ring of DNA surrounded by a cellular machinery, contained within a fatty membrane.	They consist of little more than a small piece of genetic material surrounded by a thin protein coating. Some are also surrounded by a thin and fatty envelop.
Covered by	A cell wall that consists of polysaccharides, protein and lipids.	A sheath made-up of proteins known as capsid.
Cell membrane	Present below the cell wall	No cell membrane
Genetic Material	DNA	DNA or RNA
Size	Comparatively large (approx 100 times)	Comparatively small
Type	Intercellular organisms	Intracellular organisms
Shape	Comes in three different possible shapes Cocci = sphere shape Bacilli = rod shape Spirella = spiral shape	Viruses come in all different shapes Some viruses are shaped like a space ship. They are called bacteriophages.
Host	Needs a living host, like a plant or animal	Can grow on non-living surfaces
Usefulness	Some are useful	Mostly are harmful
Antibiotics	Kill Bacteria	Cannot kill Viruses
Diseases Caused	Cholera, tuberculosis, lyme disease, pertussus, salmonella, staph infections, strep throat, leprosy, tetanus, diptheria, E.coli, flesh eating (necrotizing fascitis) and ricketts.	Flu, colds, HIV/AIDS, hepatitis, west nile, measles, herpes, shingles, chicken pox, monkey pox, polio, smallpox, ebola, and some cancers (epstein-barr) are just a few viruses that affect humans and animals.
Source of Energy	Seize energy from the same essential sources as humans, including sugars, proteins, and fats	Seize materials and energy from host cells by hijacking cellular machinery
Living	Yes	Characteristics of both living and non-living
How they are transmitted	Direct contact with an infected person Contaminated food or water (Salmonella, E.coli) Dirty objects (tetanus) Infected animals (rabies)	By direct contact with infected individuals By contact with contaminated objects (such as toys, doorknobs) By inhalation of virus-laden aerosols. (think sneezes) By animals that act as hosts (vectors)
Reproduction	Bacteria reproduce through binary fission, they split into two cells.	Virus injects itself into a living cell Protein coat is discarded Hereditary material takes over the cell’s activities Virus reproduces and the cell fills Cell splits open Viruses leave the cell and attack new cells
Motility	Bacteria move through the environment using a structure known as the flagellum.	Viruses do not have structures and thus cannot move on their own.