Bacteria vs. Virus

Bacteria (singular: bacterium) are unicellular microorganisms. They are typically a few micrometers long and have many shapes including curved rods, spheres, rods, and spirals.

A virus (from the Latin noun virus, meaning toxin or poison) is a sub-microscopic particle (ranging in size from 20–300 nm) that can infect the cells of a biological organism.

Comparison chart



Ribosomes Present Absent
Cell wall Peptidoglycan/Lipopolysaccharide No cell wall. Protein coat present instead.
Living attributes Living organism Opinions differ on whether viruses are a form of life or organic structures that interact with living organisms.
Number of cells Unicellular; one cell No cells; not living
Nucleus No No
Structures DNA and RNA floating freely in cytoplasm. Has cell wall and cell membrane. DNA or RNA enclosed inside a coat of protein.
Treatment Antibiotics Vaccines prevent the spread and antiviral medications help to slow reproduction but can not stop it completely.
Enzymes Yes Yes, in some
Virulence Yes Yes
Infection Localized Systemic
Benefits Some bacteria are beneficial (e.g. certain bacteria are required in the gut) Viruses are not beneficial. However, a particular virus may be able to destroy brain tumors (see references). Viruses can be useful in genetic engineering.
Reproduction Fission- a form of asexual reproduction Invades a host cell and takes over the cell causing it to make copies of the viral DNA/RNA. Destroys the host cell releasing new viruses.
Size Larger (1000nm) Smaller (20 - 400nm)

Contents: Bacteria vs Virus

Scanning electron micrograph of Escherichia coli bacilli
Scanning electron micrograph of Escherichia coli bacilli

Virus - Bacteria Differences

Video explaining the differences

This video explains the differences between bacteria and viruses.

Structure and contents of a typical Gram positive bacterial cell
Structure and contents of a typical Gram positive bacterial cell

Differences in reproduction

Bacteria carry all the "machinery" (cell organelles) needed for their growth and multiplication. Bacteria usually reproduce asexually. In case of sexual reproduction, certain plasmids genetic material can be passed between bacteria. On the other hand, viruses mainly carry information - for example, DNA or RNA, packaged in a protein and/or membranous coat. Viruses harness the host cell's machinery to reproduce. Their legs attach onto the surface of the cell, then the genetic material contained inside the head of the virus is injected into the cell. This genetic material can either use the cell's machinery to produce its own proteins and/or virus bits, or it can be integrated into the cell's DNA/RNA and then translated later. When enough "baby" viruses are produced the cell bursts, releasing the new viral particles. In a sense, viruses are not truly "living", but are essentially information (DNA or RNA) that float around until they encounter a suitable living host.

Transmission electron microscope (TEM) image of a recreated 1918 influenza virus
Transmission electron microscope (TEM) image of a recreated 1918 influenza virus

Living vs. Non-living

Bacteria are living organisms but opinions vary on whether viruses are. A virus is an organic structures that interacts with living organisms. It does show characteristics of life such as having genes, evolving by natural selection and reproducing by creating multiple copies of themselves through self-assembly. But viruses don't have a cellular structure or their own metabolism; they need a host cell to reproduce. It should be noted that bacterial species such as rickettsia and chlamydia are considered living organisms despite the same limitation of not being able to reproduce without a host cell. See also: Virus - Life Properties (Wikipedia)



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Comments: Bacteria vs Virus

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Anonymous comments (15)

April 30, 2009, 12:15am

no, virus are not cells, or cellular organisms. They are like machines that float around and take over living cells. They can survive without water although bacteria can also in a sense, through spores or seeds that can become alive just add water

everything alive eats something, breathes something, and excretes something as waste and has living cells with protoplasm (water) in membranes. this includes bacteria but not virus

imagine there were little machines floating in the air that were not alive, just hunks of metal. When you came in contact with them, they would use some specialized part to dock with an opening on your body. They then inject RNA or DNA into you and turn your body into a living factory to produce more machines. When the machines were fully formed, you would burst (and die) and release thousands of identical machines into the air to infect others.

— 66.✗.✗.49

March 21, 2011, 9:32pm

Question 1. How immunization works?
Answer: Immunization works with the receiver being exposed to a very small amount of a virus or a bacteria, your immune system then attacks the infection.

Question 2. List 4 different types of vaccines with brief description.
Answer: 1) Attenuated live virus is used in the measles, mumps, and rubella (MMR) vaccine and the varicella (chicken pox) vaccine.
2) Killed (inactivated) vaccines are made from a protein or other small pieces taken from a virus or bacteria
3) Toxoid vaccines contain a toxin or a chemical made by the bacteria or virus. They make you immune to the harmful effects of the infection, rather than to the infection itself.
4) Biosynthetic vaccines contain human-made substances that the immune system thinks are infectious organisms. The Hib (Haemophilus influenzae type B) conjugate vaccine is one example.

— 216.✗.✗.233

May 28, 2011, 5:27am

Given my previous comment, obviously these to statements in summary are also partially incorrect:

"The biggest difference between viruses and bacteria is that viruses must have a living host - like a plant or animal - to multiply, while most bacteria can grow on non-living surfaces.
Bacteria are intercellular organisms(i.e. they live in-between cells); whereas viruses are intracellular organisms (they infiltrate the host cell and live inside the cell). They change the host cell's genetic material from its normal function to producing the virus itself."rykews evidence

— 85.✗.✗.127

July 28, 2010, 12:47pm

Bacteria are unicellur organisms it means that a bacterium is made up of a single cell only. A virus is NOT a cell it's not even consider an organism because it does not posses any of the fundamental parts of a cell like nucleus, cytoplasm, and cell membrane. But it does have a genetic material like DNA or RNA which is vital in increasing their number. The viral DNA is capable of synthesizing new viruses inside its host cell (plant cell, animal cell, or even bacterial cell). In other words, virus is not capable of REPRODUCTION...they only multiply once they invade cell and exhibit lysis or lytic activity. Hope this helps

— 112.✗.✗.206

February 22, 2014, 4:44pm

Antibiotics - is the protective mechanism of the bacterias itself against each other, we learned that with the Fleming's discovery in the start of XX'th century and adopted to use this weapon with invention of penicilline. But bacterias in terms of all biomass are smarter - they transmitted by asexual reproduction with other bacterias genetic material contains the protection from old antibiotics which people used - so, most antibiotics are not working today.
Humans living with microorganisms all their life - in fact the number of microbes on our body is 10 times more than all human body cells (in terms of quantity).
Viruses is definitely the predators of micro-bio-world and very unique organisms - they're like from other planet, but noone sure... The interesting is that if virus is smaller than bacteria - can it attack it?
Human uses the bacterias for work of our body (esp. the ones in stomach) and we even use the parts of very old viruses for our reproduction - scientists found the parts of viruses DNA in mechanism of woman pregnancy - the child can be inside protected from mother's immune system only because of that old viruses DNA which we used for good.

— 188.✗.✗.121

May 28, 2011, 5:39am

Well it does say *most* bacteria can grow on non-living surfaces. So nit picking aside, this article is accurate.

— 24.✗.✗.203

March 16, 2014, 3:46pm

Thank you so much...You have made me pass my exams...nice information...

— 185.✗.✗.127

February 20, 2014, 3:12pm


— 101.✗.✗.9

February 12, 2014, 7:09pm

Micro organisms are juxt like human being in terms of nutrition n other requiments.

— 141.✗.✗.58

January 19, 2014, 12:05pm

Thank u so much 4 information that u gave me.

— 82.✗.✗.109

November 23, 2013, 6:12pm

thank you so much

— 24.✗.✗.65

August 23, 2013, 12:01am

great i learned a lot

— 99.✗.✗.185

November 28, 2012, 6:30am

Thanks, pretty awesome comparison!! Learned a lot today! :)

— 181.✗.✗.114

February 25, 2010, 3:57pm

bacteria and viruses are very dangerous and common to look at

— 65.✗.✗.255

December 3, 2009, 12:07am

It's correct that only bacterium can be destroyed by anti-biotics, however exposure to UV-C light renders all micro-organisms completely harmless, virus's, bacterium, mold, fungi, etc.....

— 64.✗.✗.74


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