Difference between Virus and Bacteria

Viruses and bacteria cause around 90% of the all serious infectious diseases around the world. Millions of people suffer from these diseases. However, some scientists believe, without viruses or bacteria helping the process of evolution, the world we see may be a totally different place altogether. Even though, they cause disease and misery, viruses and bacteria help humans in many ways. To understand the difference between the viruses and bacteria, one needs to understand the concept of the cell

What is a cell?

Biological dictionary term for the word cell would be “An autonomous self-replicating unit that may exist as functional independent unit of life (as in the case of unicellular organism), or as sub-unit in a multi-cellular organism (such as in plants and animals) that is specialized into carrying out particular functions toward the cause of the organism as a whole.”[1]

Structures inside a living cell are organized into number of organelles. They do specific jobs. They are made up of various proteins, carbohydrates, lipids and nucleic acids. Inside a living cell there are numerous chemical reactions happening, and it is, in fact, in a state of flux.

A cell is a fundamental unit of life. Bacteria have it. But viruses do not have a cellular structure or mechanism. However, the interesting thing is that viruses can integrate into a living cell, hijack it, and act like a living organism.  In other times it is simply a crystal with nucleic acid and some proteins. Therefore viruses change in between life and non-life.

What are the other differences between viruses and bacteria?

A smallest bacterium is hundred times bigger than the biggest virus. So there is huge difference between the sizes. In addition, viruses are always parasites. However, most bacteria are not parasites.  A bacterium can reproduce itself. But the virus needs a living cell to reproduce.

Most bacteria will be destroyed if they do not get enough nutrition. However viruses can persist in their crystalline form without any nutrition.

In addition, viral genome can be incorporated into a living cell, and this can cause cancer and other tumors. In some instances, this can cause a dormant viral infection that can come to life after some time. E.g. Herpes simplex blisters can come out when the host’s immunity is weakened.  Bacteria do not have this ability.


There are many fundamental differences between viruses and bacteria. In addition, viruses are always parasites and bacteria rarely act like parasites. However, both bacteria and viruses are elements of nature that make this world a better place.


1. http://www.biology-online.org/dictionary/Cell

2. Microbiology: Principles and Explorations by Jacquelyn G. Black