The Difference Between Bacteria and Virus

Bacteria (singular: bacterium) are unicellular micro-organisms. 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. 

Virus - Bacteria Differences 

• Viruses are the smallest and simplest life form known. They are 10 to 100 times smaller than bacteria. • 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. 

• There are some useful bacteria but all viruses are harmful. 

• Antibiotics can kill bacteria but not viruses. 

• An example of a disease caused by bacteria is strep throat and an example of an affliction caused by a virus is the flu. 

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. 

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.