EVERYDAY SCIENCE

Detailed explanation-1: -Viruses are pathogenic because they need to hijack the cellular machinery of living cells to multiply. Viruses are smaller than bacteria. The size of a typical virus is 20 to 200 nm (diameter). By looking at the size of typical bacteria and viruses, it can be said that viruses are smaller than bacteria.

Detailed explanation-2: -Size. Bacteria are giants when compared to viruses. The smallest bacteria are about 0.4 micron (one millionth of a meter) in diameter while viruses range in size from 0.02 to 0.25 micron. This makes most viruses submicroscopic, unable to be seen in an ordinary light microscope.

Detailed explanation-3: -Viruses are the smallest of all the microbes. They are said to be so small that 500 million rhinoviruses (which cause the common cold) could fit on to the head of a pin. They are unique because they are only alive and able to multiply inside the cells of other living things.

Detailed explanation-4: -The mimivirus that infects the amoeba Acanthamoeba polyphaga made newspaper headlines because its genome is much larger than those of the smallest bacteria (around 160 kb for Carsonella ruddii) and codes for more than 900 proteins (114 being vehiculated by the virion).

Detailed explanation-5: -On a biological level, the main difference is that bacteria are free-living cells that can live inside or outside a body, while viruses are a non-living collection of molecules that need a host to survive.