Virus and bacteria are infective agents that have been studied by biologists for many years. Although they are extremely small in size, these microorganisms have various features that differentiate them from other microorganisms that exist on the planet.

Below are 10 differences between virus and bacteria.

1. Definition of a virus and bacterium.
Bacteria: bacteria are defined as unicellular microorganisms present in abundance in nature. They may either be present in the environment or in living beings.
Virus: Viruses are defined as acellular infective agents that usually live and multiply inside an organism.

2. Structure of virus and bacteria.
Bacteria: Bacteria are single celled prokaryotic structures. They have a cell wall that is made up of peptidoglycans. They also contain DNA and RNA substances enclosed within the cell membrane.
Virus: viruses are acellular and do not have specific cell structures. They thus do not contain cell walls but are protected by a protein layer instead. DNA and RNA substance are enclosed within the protein coat.

3. Are virus and bacteria living or non living organisms?
Bacteria: Bacteria are living organisms that are capable of independent existence.
Virus: Viruses are generally considered non living and cannot exist independently. They require a host cell to survive and replicate.

4. Infections caused by virus and bacteria.
Bacterial infections: A few infections caused by bacteria include Step throat, Tuberculosis and urinary tract infections.
Viral infections: A few infections caused by viruses include Chickenpox, AIDS and common cold.

5. Are virus and bacteria harmless or harmful?
Bacteria: Bacteria in nature may be either harmful or useful to humans. While harmful bacteria cause diseases in living organisms, useful bacteria are necessary for various purposes. Beneficial bacteria present inside the human body help breakdown food.
Virus: Viruses are generally harmful. Weakened viruses when injected in the body can however help immunize the body to the disease that a more virulent viral infection may cause. Viruses are also very widely used in genetic engineering.

6. Treatment for viral and bacterial infections.
Bacteria: Bacterial infections can be treated by using antibiotics.
Virus: Viral infections can only be controlled. The virus cannot be destroyed using medications. Antiviral medicines however help prevent rapid growth and spread of viruses. Vaccines help immunize the body to different viruses.

7. Reproduction of virus and bacteria.
Bacteria: Bacteria reproduce in an asexual manner by a process called binary fission. In this method of reproduction, one bacterial cell cleaves to form two daughter cells.
Virus: When present outside the host organism’s body, viruses are non living. However, when the virus takes over the host cell, it uses the host cells mechanism to produce multiple copies of viral DNA. The host cell now becomes a factory aiding in replication of viral cells. The host cells are thus destroyed and replaced by the viral cells.

8. Types and classification of virus and bacteria.
Bacteria: Bacteria may be divided into 5 types depending on their shape. The 5 types of bacteria include: Coccus (spherical shaped bacteria), Bacillus (rod shaped bacteria), Vibrio (spiral shaped bacteria), Spirillum, Spirochete (cork screw shaped bacteria).
Viruses: As per the ICTV taxonomy of virus classification, there are 7 orders of virus. The 7 orders are: Caudovirales, Herpesvirales, Ligamenvirales, Mononegavirales, Nidovirales, Picornavirales, and Tymovirales

9. Size of virus and bacteria.
Bacteria are comparatively larger in size in comparison to viruses. The average bacteria measure about 1000nm while most viruses are only 20 to 400 nm big.

10. Presence of ribosome and nuclei in virus and bacteria.
Ribosome is present in bacteria but absent in virus.
Nuclei are absent in both virus and bacteria.