Bacteria: Bacteria is a constitute of a very large domain, or in other words, a kingdom of prokaryotic microorganisms. There length is usually a few micrometers. They have a wide range of shapes, like spheres to rods, and even spirals.
Virus: A virus is a very small infection that duplicates only inside the living cells of other organisms. They can infect all types of life forms, like animals, plants, bacteria, and archaea.